HomeMy WebLinkAboutItem 6f. 2025 Water Supply and Demand Assessment Item 6f
Department: Utilities
Cost Center: 6001
For Agenda of: 5/20/2025
Placement: Consent
Estimated Time: N/A
FROM: Aaron Floyd, Utilities Director
Prepared By: Nick Teague, Water Resources Program Manager
SUBJECT: 2025 WATER SUPPLY AND DEMAND ASSESSMENT
RECOMMENDATION
Receive and file the City’s 2025 Water Supply and Demand Assessment
POLICY CONTEXT
The 2025 Water Supply and Demand Assessment was prepared in accordance with the
General Plan, Water and Wastewater Management Element, Policy A5.3.1 and Water
Code §10632.1.
On July 3, 2024, the State Water Resources Control Board (SWRCB) adopted the Making
Conservation a California Way of Life regulation, establishing unique water conservation
goals for each urban water supplier in California.1 Water conservation is important to the
resilience of the City’s water resources; therefore, the City will continue to work to meet
or exceed the State’s water conservation targets.
The City also remains committed to the sustainable use of groundwater from the San Luis
Obispo Valley Groundwater Basin. In collaboration with the County, the City submitted
the San Luis Obispo Valley Groundwater Basin Water Year 202 4 Annual Report to the
State in March 2025. The City is also completing the Groundwater Contamination
Characterization Project Implementation Phase, which will drill and construct two new
groundwater production wells – serving to remove and treat contaminated groundwater
from the groundwater basin, but to also provide a new source of drinking water to the
community.
REPORT-IN-BRIEF
Results of the state-mandated 2025 Water Supply and Demand Assessment (Attachment
A, Reading File) and the City’s Water Projection Model show that the City has more than
1 The Making Conservation a California Way of Life regulation can be accessed at:
https://www.waterboards.ca.gov/conservation/regs/docs/2024/final-text-conservation-way-of-life.pdf
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ten years of water available under a drought scenario2 with current water supply and
demand conditions and future predictions concerning build-out population and associated
water demand. Monthly water supply surpluses signify that the City would not need to
enter a water shortage emergency in any month during the Current Year 3 (Fiscal Year
2025) or during a following hypothetical Dry Year (Fiscal Year 2026)4,5.
DISCUSSION
Background
The City’s 2025 Water Supply and Demand Assessment (Attachment A) was prepared in
accordance with the General Plan, Water and Wastewater Management Element
(WWME), Policy A5.3.1. and meets the State’s repo rting requirements (Water Code
§10632.1). The 2025 Water Supply and Demand Assessment provides an update on the
City’s current water supply and water demands and assesses the potential of a water
supply shortage for a hypothetical dry year.
Current Water Supply Status
The City’s water supply reservoirs (Nacimiento, Salinas, and Whale Rock) are located in
different local watersheds in northern San Luis Obispo County and along the north coast
(Figure 1). Having geographically diverse reservoirs allows the City to maximize the
capture of rainfall at various locations within San Luis Obispo County (Figure 1 and Table
1), providing benefits to the City’s water supplies beyond just rainfall received within the
City. As shown in Table 1, all watersheds that provid e water to City reservoirs received
rainfall that was comparable to the 2013-2024 median.
2 A “drought scenario” is a period when rainfall is less than normal for several weeks, months, or years, the
flow of streams and rivers declines, water levels in lakes and reservoirs fall, and the depth to water in wells
increases.
3 The Current Year for this Water Supply Assessment covers the twelve months from July 2024 through
June 2025.
4 A “Dry Year” is one in which precipitation is as low as the driest year on record.
5 The Current Year and Dry Year periods for this Water Supply Assessment are concurrent with the City’s
2025 and 2026 Fiscal Year periods, respectively.
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Figure 1: Map of reservoirs and rain gauge locations.
Table 1: Rainfall during the 2024 and 2025 Water Years (in inches)1
Rainfall Measurement
Location Watershed Median
Rainfall2
WY 2024 Total
Rainfall
WY 2025 Total
Rainfall3
Rocky Butte Nacimiento
Reservoir 28.93 71.31 34.74
Hwy 46 W 7 Mile Whale Rock
Reservoir 15.54 23.66 12.48
SLO Reservoir San Luis
Obispo Creek 15.17 24.24 14.09
Salinas Dam Salinas
Reservoir 14.33 28.52 14.24
Notes:
1. Water Year is October 1 to September 29.
2. Calculated using data from water years 2013 through 2024.
3. For the dates October 1, 2024, to April 1, 2025.
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Reservoir storage volumes as of April 1, 2025, are shown below in Table 2. The
consecutively wet winters have resulted in Nacimiento Reservoir being above 65-percent
storage capacity, and Salinas and Whale Rock Reservoirs being near capacity.
Table 2: Current Reservoir Storage and Change in Volume from Fiscal Year 2024
Reservoir
Reservoir Storage
City
Allocation
(acre-feet)1
Change from FY 2024 Current
Volume1
(acre-feet)
Total
Percent
Capacity
Storage
(acre-feet) % Capacity
Nacimiento 259,033 68% 5,482 (93,433) (25%)
Whale Rock 36,116 93% 21,451 (2,851) (7%)
Salinas 22,034 99% 19,386 (2,456.6) (11%)
Notes:
1. As of April 1, 2025.
As shown in Table 3, the City’s FY 2024 demand was 4,969 acre-feet. The total per-capita
demand during this period was 91 gallons per capita per day (GPCD). Ninety-four percent
(94%) of this demand was supplied by Whale Rock and Salinas Reservoirs, and 6% was
supplied by recycled water; water deliveries from Nacimiento Reservoir were unavailable
due to pipeline repairs.
Table 3: City Water Supply Used by Source during Fiscal Year 2024 (in acre-feet1)
Nacimiento
Reservoir
Whale Rock
Reservoir 2
Salinas
Reservoir
Recycled
Water Groundwater 3 Total City Water
Demand
- 3,409 1,251 309 0 4,969
0% 69% 25% 6% 0% 100%
Notes:
1. Values are rounded.
2. Water delivered to Cal Poly State University is excluded from the City’s water demand, as Cal
Poly has its own water storage and water diversion rights in Whale Rock Reservoir.
3. Groundwater was not used for potable purposes during Fiscal Year 202 4.
Available Supply
Water Resource Availability is calculated based on WWME, Section 3. Using this method,
the Water Resource Availability for FY 2025 is 10,246 acre-feet (Table 4), which includes
5,482 acre-feet of dependable yield from Nacimiento Reservoir, 4,910 acre-feet of safe
annual yield from Salinas and Whale Rock Reservoirs, 354 acre-feet of Recycled Water
(2024 calendar-year usage) and subtracts 500 acre-feet due to estimated reservoir
capacity losses from siltation (WWME Policy A 4.2.2).
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Table 4: Estimated Fiscal Year 2024-2025 Available Water Resources
Water Resource Acre-Feet Description
Nacimiento Reservoir 5,482 Dependable Yield 1
Salinas & Whale Rock Reservoirs 4,910 Safe Annual Yield 2
Recycled Water 354 2024 Annual Usage 3
Siltation from 2010 to 2060 (500) WWME Policy A 4.2.2 4
10,246 Total Availability5
NOTES:
1. Dependable Yield is the contractual amount of water the City has rights to from
Nacimiento Reservoir.
2. The City’s Safe Annual Yield model was updated in 2018.
3. The quantity of recycled water included (354 AF) is the actual prior year’s usage
(calendar year 2024) per General Plan Water and Wastewater Management
Element Policy A 7.2.2.
4. Reservoir siltation is a natural occurrence that reduces storage capacity over long
periods, resulting in the reduction of safe annual yield.
5. Preliminary estimate that can change with regulatory variability, climate conditions,
and other factors that may affect the City’s water supplies and customer water
uses.
Per WWME, Section 5, the City divides the total Water Resource Availability (Table 4) to
account for water supplies necessary to meet three specific community needs (Table 5):
Primary water supply – is the amount needed to meet the General Plan build-out
of the City, which is the amount of water needed to serve the City’s current and
future residential and non-residential water demand.
Reliability reserve – the buffer for future unforeseen or unpredictable long-term
water supply impacts.
Secondary water supply – the amount of water needed to meet peak water
demand periods or short-term loss of City water supply sources.
Table 5: Fiscal Year 2024 Annual Water Supply Availability (in acre -feet)1
Total Water
Availability
Primary Water
Supply
Reliability Reserve Secondary Water
Supply
10,246 7,496 1,276 1,474
NOTES:
1. Total Water Availability = Primary Water Supply + Reliability Reserve + Secondary Water Supply
Because our policies determine the supplies described above using the maximum per
capita water use allowed by State regulations (117 GPCD), the supply volumes can be
considered conservative estimations of actual demand. Using conservative estimates
allows the flexibility to respond to unforeseen impacts to water supply, or greater than
anticipated increases in demand.
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Water Supply Disruptions
High streamflow in the Salinas River corresponding to a large precipitation event on
January 9, 2023, exposed and damaged the pipeline that delivers water from Nacimiento
Reservoir to the City, disrupting delivery of water to the City. At the date that this report
was published, deliveries of water from Nacimiento Reservoir to the City were expected
to resume in July 2025. This disruption in delivery of water from Nacimiento Reservoir
has required greater than anticipated utilization of water from Whale Rock and Salinas
Reservoirs to meet water demands. As both Whale Rock and Salinas Reservoirs remain
near capacity, the actual impacts of this are currently minimal. The Water Supply and
Demand Assessment provides details on how the City will meet estimated demands while
ensuring that the reservoirs remain a reliable long-term water supply.
Water Demand
During FY 2024, the City registered 4,548 acre-feet of water use at metered locations
(Table 6). The largest demand for water in FY 2024 was for residential use (64%) and the
second largest demand for water was for commercial, industrial, and institutional uses
(24%). Demand for potable irrigation, non-potable (recycled water) irrigation, and recycled
water for construction purposes were each less than 10% of the total demand. About 372
acre-feet of potable water (8% of the City’s Water Potable Supply) were lost to distribution
system leaks and other distribution system processes. The City’s water loss is less than
the national average of about 15%.
Staff have begun migrating water meter reading from contract operations to an Advanced
Metering Infrastructure (AMI) system. AMI systems allow water consumption data to be
collected by digital water meters and transmitted to an online portal through a low-
frequency cellular transmission device, which will allow staff and community members
more visibility and accuracy of water meter reads via smart devices and will be available
on smaller timescales (by the minute instead of monthly). This will result in improved leak
detection and water budgeting.
Year-to-date (July-February) metered data for FY2025 show similar demand patterns as
FY 2024. The breakdown of metered water uses in the City by sector is as follows:
Table 6: City Water Demand by Sector During the 2024 and 2025 Fiscal Years (in acre-feet)
Fiscal
Year
Residential Commercial,
Industrial,
Institutional
Landscape
Irrigation
(Potable)
Landscape
Irrigation
(Recycled)
Construction
(Recycled)
Total
Metered
Use
FY 2024 64% 24% 7% 5% < 1% 4,548
FY 2025
(year-to-
date)1
64% 23% 8% 6% <1% 3,146
Notes:
1. July 2024 through February 2025.
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Water Shortage Assessment
The City utilizes a Water Projection Model to test both hypothetical and actual water
demand scenarios and to forecast how long water supplies will sustain the community
under specific conditions. The Water Projection Model accounts for the storage in the
City’s surface water reservoirs, other available resources, current and projected
demands, and climate data. The model uses historical hydrologic information (rainfall,
evaporation, inflow) based on the average for the worst drought period (2012 to 2014).
Per the City’s 2020 Water Shortage Contingency Plan (WSCP), the 2025 Water Supply
and Demand Assessment will utilize the Water Projection Model to determine current
demand, future demand, and any associated water shortages. Results of the Water
Projection Model show that the City has more than ten years of water available under a
drought scenario with current water supply and demand conditions.
Additionally, Water Code Section 10632.1 requires the City to evaluate water supply and
demand on a monthly time-step for the current fiscal year (FY 2024) and a hypothetical
dry year so that potential seasonal water shortages are highlighted and accounted for.
The City does not expect to enter a water shortage emergency in any month during the
Current Year or following hypothetical Dry Year.
Water Conservation
The City’s Utilities Department has improved water conservation by increasing public
outreach and communication, providing personalized assistance to community members
in detecting and resolving leaks, providing rebates for water -efficient plumbing fixtures
and appliances, promoting water-efficient landscaping and irrigation, and proactively
identifying and repairing leaks in the water distribution system. Water conservation efforts
undertaken by the community have reduced long-term water use by over 15% community
wide since the late 1980s. A comprehensive review of the City’s past, present, and future
water conservation efforts is detailed in the 2023 Water Conservation and Efficiency Plan
(Attachment B).
The City’s efforts to develop a robust and effective water conservation program have
positioned the City to meet or exceed the State’s water conservation goals. On July 3,
2024, the State Water Resources Control Board (SWRCB) adopted the Making
Conservation a California Way of Life regulation, establishing unique water conservation
goals for each urban water supplier in California. These goals reflect efficient use of water
for residential indoor demands; residential outdoor demands; outdoor irrigation at
commercial, institutional, and industrial properties; and water loss. Projection of City water
demands indicate that the City will continue to meet the State’s water conservation goals
as they become increasingly more stringent through the year 2040.
In addition to meeting State water conservation regulations, the City is also working to
prepare for regulations aimed at eliminating irrigation of non -functional turf. Assembly Bill
1572 was approved by the Governor on October 13, 2023. This bill prohibits the use of
potable water for the irrigation of nonfunctional turf located on commercial, industrial, and
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Item 6f
institutional properties, with some exceptions. Nonfunctional turf includes grass areas that
are not used for human recreation or other practical purposes. Functional turf areas that
will still be permitted to use potable water for irrigation include playing fields, recreational
areas, and areas used for community events or pet relief. The timeline for the
implementation of these regulations is as follows:
1. All properties owned by the Department of General Services, beginning January
1, 2027.
2. All properties owned by local governments, local or regional public agencies, and
public water systems, except those specified in paragraph (5) below, beginning
January 1, 2027.
3. All other institutional properties and all commercial and industrial properties,
beginning January 1, 2028.
4. All common areas of properties of homeowners’ associations, common interest
developments, and community service organizations or similar entities, beginning
January 1, 2029.
5. All properties owned by local governments, local public agencies, and public water
systems in a disadvantaged community, beginning January 1, 2031, or the date
upon which a state funding source is made available to fu nd conversion of
nonfunctional turf on these properties to climate -appropriate landscapes,
whichever is later.
The City will develop rules and guidance to facilitate compliance with these regulations.
This information will be shared with the community thro ugh workshops, community
events, handouts, social media, and other communication platforms beginning in January
2026.
Continued Communication Related to Weather Extremes and Local Conditions
The Utilities Department continues to revise its communication related to weather
whiplash (drought and flooding) and water supply topics to be able to provide succinct
information that is easily accessible to the community. While the wet winters have
provided the City with full reservoirs, it is important to ensure that the community is aware
of local water-supply conditions and that water conservation is equally important in wet or
dry years to ensure that water supplies are available to meet current and future demands.
Groundwater Management
The City and County, working together as separate Groundwater Sustainability Agencies
(GSAs) for the San Luis Obispo Valley Groundwater Basin, published the San Luis
Obispo Valley Groundwater Basin Water Year 202 4 Annual Report and submitted it to
the California Department of Water Resources (DWR) in March 2025. Pursuant to the
SGMA regulations, an annual report must be submitted to DWR by April 1 of each year
following the adoption of the Basin’s Groundwater Sustainability Plan (GSP). This is the
fourth Annual Report and documents data for Water Year 2024 (October 1, 2023, through
September 30, 2024). The annual report conveys monitoring and water use data to DWR
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Item 6f
and basin stakeholders on an annual basis to gauge performance of the Basin relative to
the sustainability goals set forth in the GSP.
Water Year 2024 was a wet year with slightly above-average rainfall and groundwater
levels throughout the basin generally remained steady from the previous year.
Groundwater measurements in the representative monitoring sites, as defined by the
GSP, ranged from about 38 feet higher to 20 feet lower than fall 2023. Overall, there was
an increase in total groundwater storage in the basin.
Use of available groundwater resources would improve resiliency in the City’s water
supply portfolio. Based on estimates published in th e San Luis Obispo Valley Basin GSP,
the City anticipates about 700 acre-feet of groundwater is available for use each year.
The City does not currently use groundwater as a drinking water source but considers
groundwater as a valuable water resource that will help the City meet its future water
supply resiliency goals. To utilize this groundwater resource, the City is completing the
Implementation Phase of the Groundwater Contamination Characterization Project, a
larger project which in its entirety aims to design, drill, and equip groundwater wells with
treatment systems capable of removing tetrachloroethylene (PCE) contamination, and to
put the City’s available groundwater to beneficial use as a drinking water source. The
project is funded through a mix of grant funding from the State of California Proposition 1
Groundwater Grant Program and City funding. Completion of the Implementation Phase
is expected in Spring 2026, at which time the City will begin using groundwater as an
additional source of supply.
Previous Council or Advisory Body Action
City Council adopted the 2024 Water Supply and Demand Assessment on June 4, 2024.
Public Engagement
The City will provide communications regarding current water supply conditions and the
results of the Water Supply and Demand Assessment by posting information and
documents on the Utilities Department website. Additionally, this information will be
incorporated into future public communications material (social media posts, radio ads,
and Farmers Market handouts) and into future water supply planning. A copy of this report
and the Water Supply and Demand Assessment will be sent to the City Planning
Commission upon receival by City Council.
ENVIRONMENTAL REVIEW
The 2025 Water Supply and Demand Assessment is not a "project" under the California
Environmental Quality Act (CEQA), because the action does not involve any commitment
to a specific project which may result in a potentially significant physical impact on the
environment, as defined by State CEQA Guidelines, Section 15378.
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Item 6f
FISCAL IMPACT
The action to receive and file the 2025 Water Supply and Demand Assessment does not
create a fiscal impact.
Budgeted: N/A Budget Year: N/A
Funding Identified: N/A
Fiscal Analysis:
Funding
Sources
Total Budget
Available
Current
Funding
Request
Remaining
Balance
Annual
Ongoing
Cost
Total $0 $0 $0 $0
ALTERNATIVES
Council could decide not to receive and file the 2025 Water Supply and Demand
Assessment and provide direction to staff on desired modifications. Should Council
select this alternative, delays beyond the July 1, 2025, due date caused by revisions may
result in noncompliance with California Water Code §10632.1.
ATTACHMENTS
A - 2025 Water Supply and Demand Assessment
B - 2023 Water Conservation and Efficiency Plan
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2025 Water Supply and Demand Assessment
For the Time Period July 1, 2024, through June 30, 2026
Whale Rock Reservoir.
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City of San Luis Obispo
2025 Water Supply and Demand Assessment
Page 2
I. INTRODUCTION
California Water Code (CWC §10632.1.)1 directs urban water suppliers (Suppliers) to conduct an Annual
Water Supply and Demand Assessment (Water Supply Assessment) for the purpose of (i) evaluating its
water supply reliability for the current year and one subsequent dry year and (ii) generating and
submitting an Annual Shortage Report by July 1 every year. The procedures for conducting a Water
Supply Assessment shall include the following:
(A) The written decision-making process that an urban water supplier will use each year
to determine its water supply reliability.
(B) The key data inputs and assessment methodology used to evaluate the urban water
supplier’s water supply reliability for the current year and one dry year, including all of
the following:
(i) Current year unconstrained demand, considering weather, growth, and other
influencing factors, such as policies to manage current supplies to meet demand
objectives in future years, as applicable.
(ii) Current year available supply, considering hydrological and regulatory conditions in
the current year and one dry year. The annual supply and demand assessment may
consider more than one dry year solely at the discretion of the urban water supplier.
(iii) Existing infrastructure capabilities and plausible constraints.
(iv) A defined set of locally applicable evaluation criteria that are consistently relied upon
for each annual water supply and demand assessment.
(v) A description and quantification of each source of water supply.
The City’s 2025 Water Supply Assessment was prepared in accordance with the General Plan, Water and
Wastewater Management Element, Policy A5.3.1.2 The methods for calculating water supply and water
demand have been modified to match the reporting requirements of the Water Supply and Demand
Assessment and are described below.
II. DECISION MAKING PROCESS
The CWC does not specify the type of year the Suppliers should use to do the Water Supply Assessment
(Calendar or Fiscal). However, the California Department of Water Resources (DWR) recommends that
the one Dry Year begins in July.3 For this Water Supply Assessment, which will be submitted by July 1,
2025, the Dry Year will therefore cover the twelve months from July 2025 to June 2026. Each subsequent
Water Supply Assessment will define the Dry Year period as July 1st of the Water Supply Assessment year
1 Cal. Water Code §10632.1. can be accessed at:
https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=WAT§ionNum=10632
2 The City’s General Plan, Water and Wastewater Element is available at:
https://www.slocity.org/home/showdocument?id=6649
3 The State of California’s Water Supply and Demand Assessment Draft Guidance states “Characteristic of a dry year
is at the discretion of the Supplier, but it should be adequately defined and ideally align with one of the WSCP water
shortage levels. The assumed Dry Year conditions are often based on a previous historic dry year, such as the driest
year on record. Suppliers presented their defined historic Dry Year in their UWMP Table 7 -1. For the purpose of this
Guidance, the Dry Year data will be applied over the twelve-month period beginning July 1st (the due date of the
current Annual Shortage Report).”
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City of San Luis Obispo
2025 Water Supply and Demand Assessment
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through June of the next calendar year. The Current Year for this Water Supply Assessment will cover
the twelve months from July 2024 through June 2025. The Current Year and Dry Year periods for this
Water Supply Assessment are concurrent with the City’s 2025 and 2026 Fiscal Year periods, respectively.
The City utilizes a Water Projection Model to test both hypothetical and actual water demand scenarios
and to forecast how long water supplies will sustain the community under specific conditions. The Water
Projection Model accounts for the storage in the City’s surface water reservoirs, in conjunction with other
available resources (i.e., groundwater and recycled water), needed to meet the City’s water demand.
The model uses historical hydrologic information (rainfall, evaporation, inflow) based on the average for
the worst drought period (2012 to 2014). Other data included in the model are:
a. Water entitlement
b. Current reservoir levels/storage
c. Average gallons per capita per day community water demand
d. Rainfall
e. Temperature
f. Evaporation
g. Existing population
h. Estimated population growth
Utilizing the Water Projection Model as part of its water supply management strategy, the City can
foresee whether a water supply shortage is anticipated in any given year and the severity of a shortage
based on the availability of the City’s different sources of supply and water demand trends. The City uses
the Water Projection Model to study the potential impacts of various intensities of drought conditions,
including increased air temperature and evaporation rates, along with decreased precipitation. Per the
City’s 2020 Water Shortage Contingency Plan, the Water Supply Assessment will utilize the Water
Projection Model to determine current demand, future demand, and any associated water shortages.4
Water supply and demand are presented in the units of acre-feet (AF). Annual available supply is
determined using existing methods (General Plan Water and Wastewater Management Element
(WWME), Section 3).5 Annual demand for the purposes of estimating Current Year and Dry Year demand
is determined using a modification of the methods described in the City’s method for determining
Primary Water Supply (WWME, Section 5) as described below. Current Year monthly demand is
determined using actual metered data when available; however, for the months when metered data
have not been collected, demand is calculated using the methods described in this report.
III. WATER SUPPLY REALIABILITY EVALUATION
This section describes the City’s various water supply sources. The City primarily utilizes water from three
surface-water reservoirs for drinking water and irrigation, and recycled water for irrigation and
construction. The effect of recent precipitation on reservoir volumes is described herein, as is the method
by which the City accounts for loss of storage capacity due to siltation.
4 The City’s Water Shortage Contingency Plan is available at:
https://www.slocity.org/home/showpublisheddocument/30334/637575513697770000
5 The City’s General Plan, Water and Wastewater Element is available at:
https://www.slocity.org/home/showdocument?id=6649
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City of San Luis Obispo
2025 Water Supply and Demand Assessment
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Description and Quantification of Each Water Supply Source
Per the General Plan Water and Wastewater Management Element, Policy A2.2.1, the City uses multiple
water sources to meet its water supply needs.6 The City has four primary water supply sources:
Nacimiento Reservoir, Whale Rock Reservoir, Salinas Reservoir, and recycled water. The City prioritizes
using contractual water supply from Nacimiento Reservoir first, with Whale Rock Reservoir and Salinas
Reservoir used as needed to meet the City’s overall potable water demand, while recycled water is used
as a non-potable source for irrigation and construction purposes within City limits. A comprehensive
upgrade to the City’s Water Resource Recovery Facility (WRRF) is currently underway and will increase
the volume of recycled water available for use in the future. Additionally, groundwater serves as the
City’s fifth supplemental water source. Substantial work efforts are being made to better understand the
City’s groundwater supplies and how they may be fully utilized in the future.
Nacimiento Reservoir
In 1959, the San Luis Obispo Flood Control and Watershed Protection District (San Luis Obispo District)
entered into an agreement with Monterey County Flood Control and Water Conservation District (now
Monterey County Water Resources Agency) to secure rights to 17,500 AF of water per year (AFY) from
Nacimiento Reservoir. Nacimiento Reservoir is located entirely within San Luis Obispo County, California
(County), and was built by Monterey County Flood Control and Water Conservation District who
continues to control reservoir ownership and operations. Nacimiento Reservoir has a storage capacity of
377,900 AF and serves the purpose of abating seawater intrusion in the groundwater aquifers of the
Salinas River Valley, while also providing flood protection and groundwater recharge for the Salinas
Valley. Of the San Luis Obispo District’s entitlement, 1,750 AFY have been designated for uses around
the lake, leaving 15,750 AFY for allocation to other areas within the County of San Luis Obispo. Water is
delivered via a 45-mile pipeline from Nacimiento Reservoir to participating agencies and cities.
The “dependable yield” from Nacimiento Reservoir is the contractual amount of water that the City has
rights to from Nacimiento Reservoir. The City’s original amount contracted for was 3,380 AFY.
Engineering studies, environmental impact reports, dependable yield analyses, and preliminary design
reports were completed to ensure water needs within the County were met. In 2004, the County
requested interested agencies to approve the contractual agreements for participation in the Nacimiento
Project. The four initial project participants included the cities of San Luis Obispo and Paso Robles, the
Atascadero Mutual Water Company, and the Templeton Community Services District. These agencies
executed participation agreements with San Luis Obispo County for entitlements of water which totaled
9,630 AF. In 2004, the County Service Area 10A in Cayucos became a project participant securing 25 AFY.
On June 29, 2004, the San Luis Obispo City Council authorized participation in the Nacimiento Water
Project for the delivery of the original 3,380 AF of water. In 2004, the County Service Area 10A in Cayucos
became a project participant (25 AFY).
In March 2016, the City Council approved the addition of 2,102 AFY from Nacimiento Reservoir to the
City’s water supply. This addition brought the City’s total Nacimiento Reservoir allocation to 5,482 AFY.
With uncertainty of future climatic conditions, regulation, and aging infrastructure, the additional supply
of Nacimiento water to the City’s portfolio reduces pressure on the use of water supplies in the Whale
Rock and Salinas reservoirs, extending these stored supplies during future critical water shortages.
6 General Plan, Water and Wastewater Management Element, Program A 2.2.1, states “The City shall utilize
multiple water resources to meet its water supply needs.”
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City of San Luis Obispo
2025 Water Supply and Demand Assessment
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During the worst-case drought on record in the region (2012 to 2014), Nacimiento Reservoir remained a
resilient water supply capable of providing a consistent and reliable source of water for San Luis Obispo
County. To confirm the prior analysis with more recent data, the City reviewed rainfall and inflow data
from 2013 which was the driest year on record. Over that year, Nacimiento Reservoir received 35,000
acre-feet of inflow. Though this is significantly below the average inflow into the reservoir, the San Luis
Obispo District’s entitlement could still be met if inflow remained at this level due to the District’s primary
rights.
High streamflow in the Salinas River corresponding to a large precipitation event on January 9, 2023,
exposed and damaged the pipeline that delivers water from Nacimiento Reservoir to the City, disrupting
delivery of water to the City. At the date that this report was published, deliveries of water from
Nacimiento Reservoir to the City were expected to resume in July 2025 through a temporary bypass. This
disruption in delivery of water from Nacimiento Reservoir is accounted for later in this report and points
to the importance of the City having a multi-source supply portfolio.
Whale Rock Reservoir
Whale Rock Reservoir is located on Old Creek Road approximately one-half mile east of the community
of Cayucos, California. The project was planned, designed, and constructed under the supervision of the
California State Department of Water Resources (DWR). Construction took place between October 1958
and April 1961. The reservoir is jointly owned by the City of San Luis Obispo, the California Men's Colony,
and the California Polytechnic State University at San Luis Obispo (Cal Poly). These three agencies form
the Whale Rock Commission which is responsible for operation and administration of the reservoir and
associated water deliveries. Day-to-day operation is provided by the City.
Whale Rock Reservoir is formed by an earthen dam and had capacity to store an estimated 40,662 AF of
water at the time of construction. The dam is 266 feet tall with a crest length of 850 feet and crest width
of 30 feet. The top of dam elevation is 232.2 feet. The Reservoir covers an area close to 600 acres. In
2022, the maximum storage capacity is 38,967 AF. The City owns 55.05 percent of the water storage
rights at the reservoir (22,364 AF). The remaining water storage rights are apportioned between the two
State agencies with Cal Poly owning 33.71 percent and the California Men’s Colony owning 11.24 percent.
Over the life of the Whale Rock Reservoir and dam, the lake has filled to capacity and the spillway has
been used 14 times, most recently spilling in February 2024.
The Whale Rock pipeline is approximately 17 miles long, connecting the reservoir to the member
agencies, and terminating at the City's Water Treatment Plant. The design capacity of the pipeline is
18.94 cubic feet per second (approximately 8,500 gallons per minute). The line consists of modified pre-
stressed concrete cylinder pipe at most locations. Cement mortar lined steel pipe is used at creek
crossings and junctions.
Salinas Reservoir
The Salinas Reservoir (also known as Santa Margarita Lake) is located on the upper Salinas River,
approximately nine miles southeast of the community of Santa Margarita. The project was originally built
by the War Department to ensure an adequate water supply for Camp San Luis Obispo, as well as the
City of San Luis Obispo. The dam and appurtenances were declared surplus by the War Department on
April 14, 1947, and the U.S. Army Corps of Engineers assumed responsibility for the facilities. On July 11,
1947, the Corps entered into an agreement with the San Luis Obispo District for the operation and
maintenance of the dam and related facilities. The City has an agreement with the Corps for use of the
reservoir, as well as a water right permit to divert water from the Salinas River for storage within the
reservoir. Salinas Reservoir is formed by a concrete arched dam. Immediately following construction, the
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reservoir had an estimated storage capacity of 24,000 AF with a surface area of 793 acres, and a drainage
area of 112 square miles. A model of the reservoir was updated in 1991 using computer calculations and
aerial photogrammetry. The San Luis Obispo County Flood Control and Water Conservation District
(District) have used the 1991 model to calculate capacity and surface area using measurements of
reservoir elevation until recently. In 2023 the District updated the model of the reservoir using a
bathymetric survey and LiDAR data to create a full coverage model of the reservoir. The 2023 updated
model resulted in a total capacity at the spillway elevation of 22,507.75 AF, a reduction of 1,522.56 AF.
The decrease in capacity can be attributed to improved data, and to siltation of the reservoir, which is
estimated at 46.14 AF/yr (mean siltation rate over 33 years).
Water is conveyed from Salinas Reservoir through 48,700 feet (9.2 miles) of 24-inch diameter reinforced
concrete pipe to a three million gallon regulating reservoir at the Santa Margarita booster pump station
near the northerly base of Cuesta Grade adjacent to Highway 101. The pipeline is designed to flow by
gravity from the Reservoir to the regulating reservoir when the lake level is above the elevation of 1,267
feet. A booster pump station at the base of the dam, consisting of two horizontal centrifugal pumps, is
capable of maintaining the rated flow of 12.4 cubic feet per second (approximately 5,565 gallons per
minute) when the water surface elevation falls below 1,267 feet.
Safe Annual Yield
Safe Annual Yield, or the maximum amount that could be withdrawn each year without drawing the
reservoir below its minimum pool constraint, for Whale Rock and Salinas reservoirs is 4,910 AFY. This
value was updated in 2018 following the addition of data from the most recent drought that ended in
2016 and analysis of three independent climate change models by the U.S. Environmental Protection
Agency (EPA), San Luis Obispo Council of Governments (SLOCOG) as part of the 2014 Regional
Transportation Plan, and Nature Communications. As a result of siltation since the original construction,
the reservoir capacity has been reduced and accounted for in the Safe Annual Yield for Whale Rock and
Salinas reservoirs.
Accounting for Siltation
Siltation at reservoirs is a natural occurrence that can reduce the storage capacity over long periods. The
reduction of available storage reduces the safe annual yield of the reservoirs. Siltation at reservoirs varies
depending on factors such as rainfall intensity and watershed management practices. Climate change
could have an impact on future water availability in the form of increased siltation in reservoirs resulting
from wildland fires which could affect the safe annual yield of the City’s reservoirs. Numerous studies
and reports addressing siltation at Salinas Reservoir have been completed. As mentioned previously, the
latest study conducted by the District in 2023, indicated that the siltation rate in Salinas Reservoir is
about 46.14 AF/yr, resulting in a decrease in reservoir capacity of 1,522.56 AF since 1991.
The Whale Rock Reservoir Bathymetric Survey and Volumetric Study was completed in May 2013. The
study concluded that sedimentation has reduced reservoir capacity by 4.2% in 52 years, but this impact,
considering 52 years of sedimentation is relatively minimal. The City has policies and programs in the
WWME to anticipate the loss of storage at Whale Rock and Salinas Reservoirs. WWME Policy A 4.2.2
relates to Accounting for Future Siltation.7 The policy states “The City will account for estimated safe
annual yield losses at Salinas and Whale Rock Reservoirs through 2060 by deducting 500 acre-feet of
available water supplies to account for these future losses.” The siltation rate will be updated as
information becomes available from subsequent siltation analyses. The siltation rate calculated by the
7 The City’s General Plan, Water and Wastewater Element is available at:
https://www.slocity.org/home/showdocument?id=6649
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District as part of the 2023 study is similar to previous estimates; therefore, the City’s policy for
accounting for safe annual yield losses remains unchanged. Accounting for siltation of reservoirs
contributes to the overall reliability of the City’s water supply portfolio as it ensures that the City is
planning for this occurrence. Siltation at Nacimiento Reservoir does not need to be accounted for in The
City’s water supply portfolio calculations because the contractual right for San Luis Obispo County
agencies is not dependent on reservoir capacity.
Recycled Water
The City’s Water Resource Recovery Facility (WRRF) produces over 3,200 AF of disinfected tertiary-
treated effluent per year. A minimum of 1,810 AF is discharged to San Luis Obispo Creek annually to
provide satisfactory habitat and flow volume for fish species (steelhead trout) within the Creek
environment. The balance makes up the City’s available recycled water resource which is available for
approved uses. A consistent flow of wastewater to the WRRF enables the City to produce a volume of
recycled water that exceeds current seasonal demand for landscape irrigation. The distribution and
delivery of recycled water is via a pump station located within the WRRF. The pump station does not
have backup power during a power outage. However, because power outage events have been
infrequent, the City’s recycled water supply is considered a reliable, non-potable water supply.
The primary use of recycled water in the City is for landscape irrigation with about 75 percent of the
City’s recycled water demand occurring from May through October. The City began issuing annual
construction water permits in July 2009. Permit holders have access to recycled water for dust control
and compaction on construction sites in the City. The City has four metered wharf head hydrant filling
stations located throughout city limits. During calendar year 2024, 354 AF of recycled water was used for
landscape irrigation and construction water. The City has identified a “seasonal surplus” of recycled
water available in excess of required discharge to San Luis Obispo Creek (4.96 AF per day as required by
the National Oceanic and Atmospheric Association, National Marine Fisheries Service in 2005). As only a
limited amount of landscape irrigation takes place from November to April (seasonal off-peak period),
more than 4 AF per day of recycled water is available during the seasonal off-peak period. An upgrade of
the WRRF is underway, which will accommodate the City’s buildout and maximize recycled water
production. These upgrades will enable the City to maximize beneficial use of recycled water, including
consideration of either direct or indirect potable reuse in the future. Until potable reuse is implemented,
the City is focused on expanding the use of recycled water within City limits to help offset potable water
use. Per the City’s 2017 Recycled Water Master Plan, recycled water use is projected to increase by 10
AF per year.
Groundwater
Although the City suspended using groundwater for potable purposes in April 2015, the City is
completing a project to build two new groundwater supply wells, with hopes of utilizing groundwater
as a supplementary drinking water source by late 2026. In July of 2020, the City received a nearly $2
million planning-phase grant, funded through Proposition 1, to study Tetrachloroethylene (PCE)
contamination of the groundwater basin. This study was completed in April 2023 and provided a more
detailed understanding of the extent of PCE contamination and identified potential remediation
options for the City to fully utilize its groundwater pumping opportunities. An additional
implementation-phase grant was awarded in March 2023; current grant funding through Proposition 1
for the implementation-phase is $7,782,800. The implementation phase will result in the construction
or outfitting of two new production wells with treatment systems to provide the City with an additional
source of potable water, while simultaneously removing contaminated groundwater from the
groundwater basin. Several new monitoring wells planned for installation in the implementation phase
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will provide an understanding of changing groundwater conditions resulting from renewed groundwater
pumping.
In January 2022, the City and the County of San Luis Obispo, acting as Groundwater Sustainability
Agencies, submitted a draft of the Groundwater Sustainability Plan (GSP) for the San Luis Obispo Valley
Groundwater Basin to the California Department of Water Resources (DWR).8 The GSP was approved
by DWR in April 2023. The GSP was a result of several years of work conducted to better understand
the hydrology of the basin and will be instrumental in guiding sustainable use of groundwater in the
basin, including the City’s utilization of groundwater as a source of supp ly. The GSP estimates a
groundwater surplus (recharge minus withdraws) of approximately 700 AFY for the portion of the
groundwater basin underlying the City .
Current Year Precipitation and Reservoir Storage
Current Year precipitation in the City is slightly below the median for Water Years 2012-2024 (Table 2);
however, reservoir levels have held steady from last year, at or near capacity. Precipitation is generally
greatest in the winter months, November through April, and can be absent in the summer months, May-
September. As of February 28, 2025, the Current Year precipitation is 10.91 inches, with 6.80 inches
falling in the month of February alone, resulting in increases in reservoir storage volumes of 54,945 AF
in Nacimiento Reservoir, 3,033 AF in Salinas Reservoir, and 513 AF in Whale Rock Reservoir9.
Table 2: Precipitation Measured at the SLO Reservoir Station1
(in inches)
Water Year Accumulation
(in inches)
2012 12.36
2013 8.50
2014 10.51
2015 11.70
2016 17.76
2017 35.34
2018 12.88
2019 27.10
2020 15.60
2021 11.62
2022 14.82
2023 51.99
2024 24.21
2012-2024 Median 16.68
2025 (October-February) 10.91
Notes:
1. Precipitation data measured at the SLO Reservoir – P (749) station can be found at:
https://wr.slocountywater.org/site/?site_id=27&view=51a30d03-3991-46af-9d23-7bc0f56a118f.
8 The San Luis Obispo Valley Basin Groundwater Sustainability Plan is available at:
https://opengov.slocity.org/WebLink/DocView.aspx?id=151703&dbid=0&repo=CityClerk&searchid=bd6f22bb-
d951-472c-848d-2d187628a2d2&cr=1
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IV. SUPPLY AND DEMAND ANALYSIS
Using the Water Projection Model described above, the City has more than ten years of water available
under a drought scenario with current water supply and demand conditions. Analysis of supply and
demand data at a monthly timescale shows that the City has the supply needed to meet monthly
demands for the Current Year and a subsequent Dry Year. This is why the City does not expect to enter
a water shortage emergency in any month during the Current Year and following hypothetical Dry Year.
This analysis provides valuable insight on the primary uses of water in the City and also highlights periods
when disruptions in delivery of water from one or more of the City’s reservoirs would be most impactful
to the City’s ability to meet demand. Monthly demands show that water supply is used primarily to meet
residential demands. Additionally, monthly demands show the seasonal variation associated with the
need for more water in the hot, dry summer months and the need for less water during the cool, wet
winter months. Ultimately, the data show that water use within the City is driven by residential use during
the dry, summer months, likely in response to outdoor irrigation needs. Because of this, water
conservation programs that target reduction in outdoor irrigation may provide the greatest water
savings.
The supply and demand analysis assumes reliable delivery of available water supplies during drought
conditions similar to those experienced in recent history. More extreme drought conditions may present
issues that decrease the volume of available water in storage or degrade the quality of water in storage.
Available water supply may also be less than estimated because of disruptions in the delivery of available
water supplies, whether temporarily caused by minor issues or prolonged disruptions caused by
catastrophic events.
Assessment Methodology: Locally Applicable Evaluation Criteria
Water supply reliability is the City’s ability to meet the water needs of its customers under varying
conditions. The City estimates annual Water Supply based on Water and Wastewater Management
Element, Section 3. The City’s fiscal year 2023-2024 water supply that was estimated using this method
is shown in Table 1. This method incorporates Safe Annual Yield from Salinas and Whale Rock Reservoirs
as determined through the City’s Safe Annual Yield Model, the City’s contractual amount of water from
Nacimiento Reservoir (Dependable Yield), the prior Calendar Year volume of Recycled Water utilized by
the City, and reduction in reservoir storage caused by siltation as directed in WWME Policy A 4.2.2. The
values shown in Table 1 are preliminary estimates that can change with regulatory variability, climate
conditions, and other factors that may affect the City’s water supplies and customer water uses. As
described in Chapter 6 of the City’s 2020 Urban Water Management Plan (UWMP)10, the City assesses
long-term water supply reliability by analyzing the hydrological variability of the City surface water
reservoirs (Salinas, Whale Rock, and Nacimiento). This analysis is done using the City’s Water Projection
model and applies worst-case drought conditions according to guidelines set forth in the UWMP plan
documentation.
10 The City’s 2020 Urban Water Management Plan can be accessed from the California Department of Water
Resources, WUEdata Portal at: https://wuedata.water.ca.gov/uwmp_plans.asp?cmd=2020
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Table 1: Estimated Fiscal Year 2024-2025 Annual Water Supply
Water Resource Acre-Feet Description
Nacimiento Reservoir 5,482 Dependable Yield 1
Salinas & Whale Rock Reservoirs 4,910 Safe Annual Yield 2
Recycled Water 354 2024 Annual Usage 3
Siltation from 2010 to 2060 (500) WWME Policy A 4.2.2 4
10,246 Total Availability5
NOTES:
1. Dependable Yield is the contractual amount of water the City has rights to from
Nacimiento Reservoir.
2. The City’s Safe Annual Yield model was updated in 2018.
3. The quantity of recycled water included (354 AF) is the actual prior year’s usage
(calendar year 2024) per General Plan Water and Wastewater Management Element
Policy A 7.2.2.
4. Reservoir siltation is a natural occurrence that reduces storage capacity over long
periods, resulting in the reduction of safe annual yield.
5. Preliminary estimate that can change with regulatory variability, climate conditions, and
other factors that may affect the City’s water supplies and customer water uses.
Generally, the City accounts for annual demand, or the water supplies necessary to meet community
needs, using the methods detailed in the General Plan Water and Wastewater Management Element
(WWME), Section 5.11 The amount of water needed to serve the City’s future residential and non-
residential water demand is termed the primary water supply. The primary water supply is calculated
using the build-out population identified in the General Plan, Land Use Element (2014) and the maximum
allowed per capita water use under Senate Bill X7-7, which is 117 gallons per capita per day (GPCD).12
Previous Water Supply and Demand Assessments utilized this method to estimate future demand;
however, this resulted in large overestimations when compared to actual demand. These
overestimations of water demand did not reflect the recent historical demand, presenting difficulties in
assessing the City’s short-term water supply and demand scenario.
For this Water Supply and Demand Assessment, Current Year and Dry Year water supplies were
calculated using the estimated supply available from Nacimiento Reservoir (see proceeding text
regarding supply disruptions), the full safe annual yield from Salinas and Whale Rock reservoirs, recycled
water use from the previous calendar year plus 10 AFY, and a reduction in 500 AFY to account for
siltation. To accurately assess the City’s short-term potable water demand, Current Year and Dry Year
demands were calculated by multiplying the previous fiscal year’s potable water GPCD by the estimated
population for fiscal years 2025 and 2026, respectively.13 The annual water supply and demand volumes
calculated using the methods described above are converted to monthly volumes for the purposes of
this Water Supply Assessment so that potential seasonal water shortages are highlighted.
11 The City’s General Plan, Water and Wastewater Element is available at:
https://www.slocity.org/home/showdocument?id=6649
12 Senate Bill No. 7 – Water conservation, is available at:
https://leginfo.legislature.ca.gov/faces/billNavClient.xhtml?bill_id=200920107SB7
13 The potable water demand for fiscal year 2024 was 79. Per the City’s General Plan, population growth is estimated
to be 1% per year.
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When utilizing the Water Projection Model to estimate long-term water supply and demand, GPCD
decreases in accordance with the 2020 Water Shortage Contingency Plan (WSCP). For example, water
demand is calculated using an initial value of 117 GPCD and decreases by ten percent (corresponding to
a ten-percent decrease in water use) to 105 GPCD when available supply is less than 5-years of estimated
annual demand. This ten percent reduction is in alignment with the demand reduction that the City
projects it would achieve from conservation measures outlined in the WSCP.
Existing Infrastructure Capabilities and Plausible Constraints
The utilization of water from three separate reservoirs provides the City with operational flexibility to
meet water demands while maintaining optimal storage volumes in each reservoir; however
environmental factors can inhibit reservoir storage or prevent utilization of stored water by degrading
water quality. While inflow to Nacimiento has proven to be sufficient during the worst drought in recent
history, it is conceivable that in the most extreme drought, when precipitation is near zero, that inflow
is less than the City’s contractual amount. The City has not typically experienced significant water quality
issues with water stored in its reservoirs, but extreme heat and low reservoir levels associated with
drought conditions are ideal conditions for biological processes that can impair water quality, including
growth of algae, which can lead to secondary water quality complaints related to taste and odor. The
City’s water treatment plant is capable of producing water that meets all state and federal standards,
even as water quality is deteriorated by ongoing drought.
Generally, the City satisfies demand without utilizing the full dependable yield from Nacimiento Reservoir
because pipeline capacity constraints and treatment operation only allow for the delivery and treatment
of approximately 4,500 AFY. Projects are being developed to allow for the full utilization of dependable
yield from Nacimiento Reservoir in preparation for future periods when demands require the full
available water supply. Should the City need to utilize its full entitlement to Nacimiento for any reason,
it could modify plant operation to accommodate this need. Because the City relies primarily on water
supplied by its reservoirs, disruptions in delivery of water from a reservoir could be caused by damage
to existing infrastructure. While temporary disruptions in water supply availability can be mitigated
through utilization of water from the other available reservoirs, prolonged disruptions could result in
water shortages.
The City is expanding its groundwater program and considering potable reuse of recycled water to
provide water supply redundancy and increased operational flexibility in extreme drought scenarios and
during disruptions in delivery of water from reservoirs. Additionally, the City produces recycled water
that can be used to offset potable demand and during disruptions of water supply. Ultimately the City
proactively pursues projects that help gain a better understanding of potential issues that may threaten
its water supply and how to mitigate them.
Current Year Water Supply and Demand Assessment
Analysis of the supply and demand data from the previous year allows for a better understanding of how
annual demand is met with the available water supplies. As shown in Table 3, the City’s 2023-2024 Fiscal
Year demand was 4,713 AF. The per-capita demand, including recycled water, during this period was 86
GPCD. Ninety-three percent (93%) of this demand was supplied by Whale Rock and Salinas Reservoirs,
and 7% was supplied by recycled water; water deliveries from Nacimiento Reservoir were unavailable
due to pipeline repairs.
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Table 3: City Water Supply by Source during the 2023-2024 Fiscal Year1
(in acre-feet)
Nacimiento
Reservoir
Whale Rock
Reservoir 2
Salinas
Reservoir
Recycled
Water Groundwater 3 Total City Water
Demand
- 4,027 377 309 0 4,713
0% 85% 8% 7% 0% 100%
Notes:
1. Values are rounded.
2. Water delivered to Cal Poly State University at San Luis Obispo (Cal Poly) is excluded from the City’s water demand, as Cal
Poly has its own water storage and water diversion rights in Whale Rock Reservoir.
3. Groundwater was not used for potable purposes during Fiscal Year 2023-2024.
Current Year available water supply is 6,875 AF; 4,742 AF potable water and 2,133 AF non-potable water
(Table 4). In the Current Year the City planned to utilize its water sources similarly to Fiscal Year 2021-
2022 by prioritizing water from Nacimiento Reservoir to preserve or increase storage volumes in Whale
Rock and Salinas Reservoirs. However, the damage to the Nacimiento pipeline, previously detailed in this
report, is estimated to prevent the City from using water from Nacimiento for the remainder of the fiscal
year. The City’s Current Year water supply (Table 4) summarizes actual supply volumes delivered to the
City’s distribution system for the period July 2024 through February 2025 and estimated supply volumes
for March through June 2025. The water supply volumes reflect the absence of Nacimiento Reservoir
and the increased utilization of water from Whale Rock and Salinas Reservoirs and the associated safe
annual yield. Utilizing a volume less than or equal to the safe annual yield helps to ensure that the
reservoirs remain a reliable long-term water supply; however, short-term exceedance of the safe annual
yield should not negatively impact long-term water supply – especially at times when the reservoirs are
at storage capacity. The subtraction of 42 AF for March through June 2025 represents the City’s methods
to account for siltation in the reservoirs (500 AFY divided among twelve months) and ensures that the
volume of water used from Whale Rock and Salinas Reservoirs is in alignment with the General Plan
Water and Wastewater Management Element (WWME), Section 5.
The Current Year estimated potable demand is 4,742 AF (Table 5). Using actual data for the period July
2024 through February 2025, the potable water GPCD is 92. Thanks to a history of collaboration between
the City and its community members, community-wide water conservation has resulted in more efficient
water use over the last 15 years. This water conservation ethic is supported by City programs such as the
water conservation rebate program, school education program, community outreach program, customer
water audits, and the retrofit upon sale program. Additionally, the City is improving the water efficiency
of its operations by identifying and repairing leaking infrastructure, annually testing and upgrading water
meters, and supplying parks with non-potable recycled water for irrigation. The City will conduct regular
assessments of the water conservation program to ensure the most effective use of City resources to
provide the greatest water savings.
Current Year water supply and demand data are shown on a monthly time-step in Table 5. The values
demonstrate the seasonal differences in demand and the supplies needed to meet those demands. The
City is not anticipating entering into a water shortage emergency at any point in the Current Year. The
Current Year non-potable demand is 304 AF. This represents recycled water used for irrigation and
construction purposes and acts to offset potable water use. The Current Year non-potable supply and
demand assessment shows large surpluses for every month and a total annual surplus of about 1,829 AF.
The total non-potable supply includes the total volume of water treated at the City’s WRRF minus 4.9 AF
per day creek discharge requirement. The non-potable supply and demand assessment provides insight
on seasonal fluctuations in non-potable water supply and will assist the City in determining the ability to
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meet increases in future demands for irrigation and the volume of water available for potable reuse
projects.
Dry Year Water Supply
The City’s estimated Dry Year water supply is 9,034 AF (potable supply plus recycled water for non-
potable reuse in Table 6). The Dry Year water supply is equivalent to the Fiscal Year 2025-2026 supply
and reflects a restricted supply from Nacimiento Reservoir once temporary repairs are completed in July
2025. The City’s potable and non-potable water supplies are shown on a monthly time-step in Table 6.
Dry Year Unconstrained Demand
The Dry Year estimated potable demand is 4,737 AF (Table 7). Actual Dry Year demand be lower or
greater than the estimated demand because of more efficient water use and variations in water needs
caused by annual climate variations. Most of the City’s potable demand is for single-family residential
use (42%), followed by muti-family residential (19%), and commercial (19%). Demands for industrial,
institutional, and dedicated landscape meters are each below ten percent of the total annual demand.
Single-family and multi-family residential demands are greatest during the period May through October
when precipitation is generally low. This suggests that residential demand is driven by outdoor irrigation
and the increased demand for irrigation during dry periods. Non-potable water is estimated to offset
about 329 AF of potable demand during the Dry Year (Table 7).
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Table 4: Current Year 2024-25 Water Supply, in acre-feet
Potable Water Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Total
Nacimiento Reservoir 0 0 0 0 0 0 0 0 0 0 0 0 0
Salinas and Whale Rock Reservoirs3 484 471 461 476 388 351 384 340 328* 349* 430* 448* 4,910*
Groundwater 0 0 0 0 0 0 0 0 0 0 0 0 0
Siltation from 2010 to 2060 - - - - - - - - (42) (42) (42) (42) (168)
Total by Month (Potable) 484 471 461 476 388 351 384 340 286* 307* 388* 406* 4,742*
Non-Potable Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Total
Recycled Water for non-potable use4 41 42 33 30 17 8 10 8 11* 24* 33* 37* 294*
Recycled Water available for use 68 58 86 85 149 154 185 260 289* 204* 168* 133* 1,839*
Total by Month (non-potable) 109 100 119 115 166 162 195 268 300* 228* 201* 170* 2,133*
Notes:
1. Values are rounded to the nearest whole number.
2. * Denotes estimated values.
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Table 5: Current Year 2024-25 Water Supply and Demand, in acre-feet
Potable Water Jul Aug Sep Oct Nov Dec Jan Feb Mar* Apr* May* Jun* Total*
Unconstrained
Demand 484 471 461 476 388 351 384 340 286 307 388 406 4,742
Total Water Supply2 484 471 461 476 388 351 384 340 286 307 388 406 4,742
Surplus/Shortage 0 0 0 0 0 0 0 0 0 0 0 0 0
% Surplus/Shortage 0% 0% 0% 0% 0% 0% 0% 0% 0% 0% 0% 0% 0%
State Standard
Shortage Level 0 0 0 0 0 0 0 0 0 0 0 0 0
Non-Potable Jul Aug Sep Oct Nov Dec Jan Feb Mar* Apr* May* Jun* Total*
Unconstrained Demand 41 42 33 30 17 8 10 8 11 24 37 43 304
Total Water Supply3 109 100 119 115 166 162 195 268 300 228 201 170 2,133
Surplus/Shortage 68 58 86 85 149 154 185 260 289 204 164 127 1,829
% Surplus/Shortage 62% 58% 72% 74% 90% 95% 95% 97% 96% 89% 82% 75% 86%
Notes:
1. * Denotes estimated values.
2. Values are rounded to the nearest whole number.
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Table 6: Estimated Dry Year 2024-25 Water Supply, in acre-feet
Water Supply
Source
Additional
Detail on Water
Supply
Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Total
Annual
Water
Supply
Nacimiento
Reservoir
From dependable
yield1
249 234 218 234 207 184 161 164 179 190 235 245 2,500
Salinas and
Whale Rock
Reservoirs
From safe annual
yield
488 459 428 459 406 361 318 322 352 374 462 481 4,910
Groundwater Supplier-produced - - - - - - - - - - - - -
Other Decrease in
available supply
from siltation in
reservoirs
(41) (41) (41) (41) (42) (42) (42) (42) (42) (42) (42) (42) (500)
Total Potable 696 652 605 652 571 503 437 444 489 522 655 684 6,910
Recycled Water
for non-potable
reuse
For irrigation and
construction uses
41 42 36 42 34 17 5 5 11 24 34 38 329
Recycled Water
available for use
Produced by the
WRRF that is not
allocated for non-
potable reuse or
creek discharge
requirements
65 60 89 115 91 117 240 224 289 204 168 133 1,795
Total Non-Potable 106 102 125 157 125 134 245 229 300 228 202 171 2,124
1. Restricted supply from Nacimiento due to service through temporary connection.
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I. PLANNED SHORTAGE RESPONSE ACTIONS
The City does not plan to implement a water shortage response in the Current Year or following Dry Year;
however, the City’s Water Shortage Contingency Plan (WSCP) provides a framework for responding to
water shortages when necessary.14 The City’s water shortage response is dependent on the ability to
temporarily augment supply and/or reduce water demand. The goals of the WSCP are to extend the
City’s available water resources long enough to gain another winter rainfall period which could serve to
add to reservoir storage. Extending available water resources through water demand reductions provides
time for the City to bring on supplemental water supplies to meet demand. The City’s water shortage
response would combine a variety of strategies including outreach, indoor water efficiency regulations,
and outdoor irrigation restrictions, each increasing in intensity as the shortage persists and the City’s
water supplies are further restricted. If necessary, implementation of these restrictions is critical to
conserve the City’s water supply for the greatest public benefit regarding domestic use, sanitation, and
fire protection.
The City reads water meters monthly to ensure water consumption data is collected for tracking and
analysis, as well as meeting state reporting requirements. Monitoring and reporting water use metrics
are fundamental to water supply planning and management. Monitoring is essential in evaluating the
effectiveness of expected response actions and identifying the need for new actions. While compliance
tracking helps to ensure the effectiveness of enforcement programs. To monitor the functionality of the
WSCP and ensure effectiveness, staff will track community response to water demand reduction
measures, public outreach, enforcement, and other administrative actions at each water shortage
response stage. This will include a review of monthly water consumption data for each customer class
and evaluation of associated revenue and expenditure impacts. Based on these analyses, staff will
recommend program refinements to the City Council as water shortage stages progress.
14 The City’s Water Shortage Contingency Plan is available at:
https://www.slocity.org/home/showpublisheddocument/30334/637575513697770000
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Table 7: Dry Year 2024-25 Unconstrained Demand, in acre-feet
Water Use
Projected Monthly Water Demand1 Total
Annual
Demand
Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun
Demands Served by Potable Supplies
Single Family 175 183 177 176 154 126 121 129 131 153 168 174 1,867
Multi-Family 85 89 96 98 90 82 81 83 82 91 89 86 1,052
Commercial 80 82 77 79 73 68 59 65 66 68 70 77 864
Industrial 15 15 14 13 9 7 6 7 7 10 12 13 128
Institutional/Government 3 3 3 4 3 3 3 2 3 3 3 3 36
Landscape 47 48 44 38 25 11 9 14 15 26 38 44 359
Water Loss 41 42 41 41 35 30 28 30 30 35 38 40 431
Total by Month (Potable) 446 462 452 449 389 327 307 330 334 386 418 437 4,737
Demands Served by Non-Potable Supplies2
Landscape 36 37 30 26 16 6 6 9 10 19 32 36 263
Golf Course Irrigation 5 5 3 3 2 0 1 1 1 3 4 5 33
Construction 4 5 4 4 2 0 1 2 1 2 3 4 32
Utilities 0 0 0 0 1 0 0 0 0 0 0 0 1
Total by Month (Non-Potable) 45 47 37 33 21 6 8 12 12 24 39 45 329
Notes:
1. Estimated values.
2. Non-potable water treated to tertiary level.
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Table 8: Dry Year 2023-24 Water Supply and Demand, in acre-feet
Potable Water Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Total
Anticipated Unconstrained
Demand 446 462 452 449 389 327 307 330 334 386 418 437 4,737
Anticipated Total Water Supply 696 652 605 652 571 503 437 444 489 522 655 684 6,910
Surplus/Shortage 250 190 153 203 182 176 130 114 155 136 237 247 2,173
% Surplus/Shortage 36% 29% 25% 31% 32% 35% 30% 26% 32% 26% 36% 36% 31%
State Standard Shortage Level 0 0 0 0 0 0 0 0 0 0 0 0 0
Non-Potable Water Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Total
Anticipated Unconstrained
Demand 45 47 37 33 21 6 8 12 12 24 39 45 329
Anticipated Total Water Supply 106 102 125 157 125 134 245 229 300 228 202 171 2,124
Surplus/Shortage 61 55 88 124 104 128 237 217 288 204 163 126 1,795
% Surplus/Shortage 58% 54% 70% 79% 83% 96% 97% 95% 96% 89% 81% 74% 85%
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II. SUMMARY
Based on the findings from this Water Supply Assessment, the City does not expect to enter a water
shortage emergency and will not need to implement water shortage response actions. In fact, the Water
Supply Assessment shows that the Dry Year the City will have a water supply surplus on an annual and
monthly timestep. The City will continue to monitor its supply and demand using its Water Projection
Model to ensure that any water shortage emergencies may be identified well in advance so that
programmatic and operational changes can be made to mitigate their effects. Finally, this Water Supply
Assessment assumes reliable delivery of available water supplies during drought conditions similar to
those experienced in recent history. Decreases in water availability caused by extreme drought
conditions or disruptions in the delivery of available water supplies may create unexpected water
shortage emergencies. If such water shortage emergencies arise, the City is prepared to implement its
WSCP to extend the City’s available water resources long enough to gain additional winter rainfall periods
which could serve to add to reservoir storage or to bring on supplemental water supplies to meet
demand.
In summary, the City maintains a robust water supply portfolio that can meet current and future
demands, including during dry periods. To plan for potential future dry years, the City has secured a
multi-source supply that provides reliability and operational flexibility. The City’s estimates of water
supply and demand account for both current and future build-out demands to ensure adequate water
supply, and the use of conservative estimates provides a buffer that reduces the potential for water
shortages even during unexpected disruptions in water supply or greater than expected increases in
demand. This buffer is in part to the long-standing history of water conservation by the City and its
community members, making water conservation a reliable component of the City’s water shortage
mitigation strategy. Additionally, the City is working to expand the use of recycled water within its limits
to offset additional potable water use and to develop groundwater and potable reuse programs to
provide supplementary sources of potable water supply that provide further operational flexibility during
disruptions in water deliveries from reservoirs.
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Page 115 of 555
Table of Contents
1. Introduction ......................................................................................................................... 6
2. Service Area and Water System Characteristics ................................................................. 8
3. Water Supply and Demand ................................................................................................13
4. Historical and Current Water Conservation Program ..........................................................22
5. Regulatory Compliance ......................................................................................................29
6. Evaluation of Long-Term Water Conservation Measures ...................................................33
7. Final Water Conservation Program ....................................................................................38
8. Conclusion .........................................................................................................................45
9. Appendix ............................................................................................................................47
List of Tables
Table 1. Projected and Actual City Population...........................................................................10
Table 2. Annual Water Supply for Fiscal Year 2022-23. ............................................................14
Table 3. Water Supply Use by Source for Fiscal Year 2023. .....................................................15
Table 4. Water Demand by Customer Category for Fiscal Year 2022-23. .................................16
Table 5. Key Water Loss Audit Metrics. ....................................................................................24
Table 6. Results of the 2022 Survey of Businesses' Interests in Water Conservation Measures.
.................................................................................................................................................35
Table 7. Quantity and Budget Allocated for Water Conservation Plan C. ..................................35
Table 8. Projected Water Demands. .........................................................................................40
Table 9. Estimated CO2 Savings from Implementation of the Selected Water Conservation
Program. ...................................................................................................................................42
Table A 1. Commercial, Industrial, and Institutional (CII) Water Account Classifications ...........47
Table A 2. Plan A Water Conservation Measure Parameters. ...................................................49
Table A 3. Benefit-Cost Ratio for Conservation Measures Included in Plan A. ..........................50
Table A 4. Plan B Water Conservation Measure Parameters. ...................................................51
Table A 5. Plan C Water Conservation Measure Parameters. ...................................................53
Table A 6. Implementation Schedule. ........................................................................................54
List of Figures
Figure 1. Map of Key Water Infrastructure. ................................................................................. 9
Figure 2. Water Demand by Source (FY2000-2022). ................................................................15
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City of San Luis Obispo Water Conservation and Efficiency Plan P a g e | 3
Figure 3. Actual City Water Demand Versus SB X7-7 Estimated Water Demand (FY 2000 - FY
2023). .......................................................................................................................................18
Figure 4. Historical Storage Volume, in Acre-Feet, in Salinas and Whale Rock Reservoirs, and
Projected Storage Volume Through an Extended Drought Period. ............................................20
Figure 5. Screenshot of the City of San Luis Obispo's Plumbing Retrofit Portal. .......................31
Figure 6. City of San Luis Obispo Annual Per Capita Water Use (in gallons per capita per day,
GPCD) Versus Population and the Target Per Capita Use as Determined by SB X7-7, 2000-
2022. .........................................................................................................................................32
Figure 7. Estimated Water Savings and Program Costs for Water Conservation Plans A-C. .....37
Figure A 1. Plan A Annual Program Water Savings. .................................................................51
Figure A 2. Plan B Annual Program Water Savings. .................................................................52
Figure A 3. Benefit Cost Ratio Versus Expected Water Savings ...............................................52
Figure A 4. Plan C Annual Program Water Savings. .................................................................53
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City of San Luis Obispo Water Conservation and Efficiency Plan P a g e | 4
List of Abbreviations and Acronyms
AB Assembly bill
AF Acre-feet
AFY Acre-feet per year
AMI Advanced metering infrastructure
AWE Alliance for Water Efficiency
AWWA American Water Works Association
CALGreen California Code of Regulations, Title 24, California Green Building Standards
Code
Cal Poly California Polytechnic State University
CII Commercial, industrial, and institutional
CO2 Carbon dioxide
CWC California Water Code
DIM Dedicated irrigation meter
FY Fiscal year
GHG Greenhouse gas
GPCD Gallons per capita per day
HCF Hundred cubic feet
kWh Kilowatt hour
Mgd Million gallons per day
MFR Multi-Family Residential
MWELO Model Water Efficient Landscape Ordinance
PG&E Pacific Gas and Electric
psi Pounds per square inch
R-GPCD Residential gallons per capita per day
SB Senate Bill
SCADA Supervisory Control and Data Acquisition
SFR Single-Family Residential
UWMP Urban Water Management Plan
UWUO Urban Water Use Objective
WRRF Water Resource Reclamation Facility
WSCP Water Shortage Contingency Plan
WTP Water Treatment Plant
WWME Water and Wastewater Management Element
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Page 119 of 555
1. INTRODUCTION
Purpose and Scope
The City of San Luis Obispo (City) has developed the Water Conservation and Efficiency Plan to
ensure the sustainable management of its water resources while meeting the needs of a growing
community and the demands of evolving water-use regulations. The purpose of this plan is to
guide the implementation of water conservation measures that maximize water savings using
available financial and staffing resources. Water conservation includes activities designed to (1)
reduce the demand for, and improve use efficiency of, water use (demand management), (2)
reduce losses and waste of water, and (3) improve land management practices, such as soil
improvement and low-impact development stormwater retention.
The City is committed to maintaining its long history of water conservation and water supply
reliability. As a continuation of this commitment, the Water Conservation and Efficiency Plan
includes a detailed assessment of historical and current water conservation efforts, a
comprehensive evaluation of long-term water conservation measures, and thoughtful selection of
water conservation measures to be incorporated into the City’s future water conservation
programing. The Water Conservation and Efficiency Plan also aims to estimate water supply and
demand changes in response to water use efficiency regulations, implementation of water
conservation measures, and population growth. This plan differs from the City’s Water shortage
Contingency Plan (WSCP)1 in that it defines actions the City will take to proactively conserve
water, while the WSCP defines water conservation actions that will be taken in response to
various degrees of drought.
1 The City’s 2020 Water Shortage Contingency Plan can be accessed at:
https://www.slocity.org/home/showpublisheddocument/31039/637673766931570000
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City of San Luis Obispo Water Conservation and Efficiency Plan P a g e | 7
Objectives
The five primary objectives of this plan are to:
1. Develop cost-effective water conservation measures that maximize opportunities to meet
the future water needs of the community.
2. Offset and/or delay the need to construct additional water supplies or upsize treatment
and distribution infrastructure.
3. Offset and/or reduce ratepayer costs for the treatment and delivery of safe water and the
treatment of wastewater.
4. Meet state and federal water conservation mandates.
5. Foster environmental stewardship through the implementation of responsible and
innovative water use practices.
To achieve these objectives, the City will continue to strive to be more water-efficient within its
own operations and maintenance practices and encourage customers to be more water efficient
through the implementation of various water conservation measures. The Water Conservation
and Efficiency Plan will act as a roadmap for the City to meet its water conservation goals, while
also ensuring that its water resources are sustainable for future generations.
Plan Development and Public Participation
The City’s Water Conservation and Efficiency Plan was developed with valuable input and
recommendations to ensure that it reflects the needs of the community. Stakeholders included
City staff and members of the community-at-large. The plan will be regularly reviewed and revised
to reflect new technology and industry practices, and staff will seek public input during these
updates to ensure continued community involvement. Revisions will be made with careful
consideration of the benefits and costs associated with the most current water conservation and
efficiency industry standards. By continuing to engage with a wide range of stakeholders, the
Water Conservation and Efficiency plan will continue to promote the responsible use of the City’s
water resources for all community members.
Plan Elements
The City’s approach to water conservation is tailored to the unique needs and characteristics of
the San Luis Obispo community. The Water Conservation and Efficiency Plan includes a
comprehensive analysis of the City’s water service area, current and historical water supply and
demand patterns, and relevant conservation regulations. Next, an evaluation of potential long-
term water conservation measures is conducted using the Alliance for Water Efficiency (AWE)
Conservation Tracker Tool. With this information, the plan identifies a final water conservation
program and sets specific targets for reducing usage in residential and commercial sectors. This
section also outlines the measurable objectives the City aims to achieve to meet those targets.
Lastly, the Water Conservation and Efficiency Plan describes an implementation plan that the City
will use to regularly monitor and evaluate the effectiveness of the water conservation measures
that have been implemented. Overall, the Water Conservation and Efficiency Plan acts as an
important tool in evaluating the City’s approach to water conservation and establishing a more
sustainable and resilient water supply for the community.
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2. SERVICE AREA
AND WATER
SYSTEM
CHARACTERISTICS
Service Area
The City of San Luis Obispo is located about half-way between Los Angeles and San Francisco,
California (Figure 1) and has a total area of 13.2 square miles. Situated in a coastal valley
approximately ten miles inland from the Pacific Ocean, the City’s Mediterranean climate provides
for mild and dry summers and cool winters, with an annual average of about 20 inches of
precipitation. Summers are generally warm and sunny, often with morning fog from the Pacific
coast. Winters are generally mild, though below freezing lows may be expected during the winter.
Temperatures vary widely, with 80° F readings in January and February not uncommon. Because
the City receives water from surface water reservoirs located in different watersheds, climate data
specific to the areas surrounding the reservoirs are utilized in water management models.
Demographic Forecasts
The City’s January 2023 population was 47,788.2 From 2012 to 2022, the City grew by 235 people
which was below the City’s General Plan one percent growth maximum3. The City’s future growth
is projected to be in specific plan areas, as well as infill and intensification of existing developed
areas, such as the City’s’ downtown.
2 The State of California Department of Finance, Population and Housing Estimates for Cities, Counties, and the
State – January 1, 2022 and 2023 can be accessed at: https://dof.ca.gov/forecasting/demographics/estimates-e1/
3 The City of San Luis Obispo General Plan can be found at: https://www.slocity.org/government/department-
directory/community-development/planning-zoning/general-plan
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City of San Luis Obispo Water Conservation and Efficiency Plan P a g e | 9
Figure 1. Map of Key Water Infrastructure.
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City of San Luis Obispo Water Conservation and Efficiency Plan P a g e | 10
The City uses the growth rate and population projections from the City’s General Plan Land Use
Element (1% annual growth rate and 57,200 persons in 2035). To comply with State
requirements, the City’s 2020 Urban Water Management Plan (UWMP)4 projected population
through 2040. The City assumed an annual population growth of one percent for the five years
from 2035 to 2040, yielding a future population of 60,118 in 2040. Table 1 provides the City’s
actual 2020 population and population projections to 2040.
Table 1. Projected and Actual City Population.
2020 2025 2030 2035 2040
Land Use Element (2014),
Projected Population1
48,826 51,317 53,934 57,200 60,118
Actual City Population2 45,920 --- --- --- ---
1City of San Luis Obispo, General Plan, Land Use Element, Table 3, 2014.
2Population estimate for the City of San Luis Obispo is from the California Department of Finance website at:
www.dof.ca.gov/forecasting/Demographics/Estimates/e-1/
The City is a civic, economic, and cultural hub on the Central Coast. With an influx of employees
to major regional employers, the City has an estimated daytime population of up to 90,000
persons. Public sector jobs account for a sizeable portion of the job market, including California
Polytechnic State University (Cal Poly) and the County of San Luis Obispo. Per the June 2019
Cal Poly Campus Master Plan5, student enrollment, faculty, and staff is anticipated to grow from
just over 24,000 at the 2015 baseline mark, to nearly 29,000 people by the 2035-36 academic
year (an average increase of 200 students per year). Although Cal Poly plans to increase on
campus housing and the university has its own water supply source, large portions of the student,
faculty, and staff populations reside within City limits and visitors frequently visit or stay in the City
for university related events. In addition to local events, the City is also a popular tourist
destination due to its proximity to beaches and open space areas, historic downtown, and its
overall vitality. The City’s tourism is at its peak during the summer; however, Cal Poly is also out
of session at this time, thus reducing the overall daily population served by the City during the
summer months.
Water System
The City utilizes water from three surface-water sources for potable (drinking-water) purposes
and recycled water from its Water Resource Recovery Facility (WRRF) for non-potable uses.
Several upgrades of the City’s Water Treatment Plant (WTP) have improved treatment plant
resiliency and capacity to meet the City’s evolving demands. Treated water is delivered from the
WTP to water customers through a system of water mains, storage tanks, and pump stations. The
City performs regular system maintenance to ensure reliable water delivery and to reduce water
loss. Water demand is measured at customer meters monthly using a contract meter reading
service, which allows prompt, accurate, and efficient meter reading. Monthly meter reads also
allow the City’s Water Resources section to respond to potential concerns of water loss in a timely
manner. To increase water efficiency in the community’s water distribution and treatment
4 The City of San Luis Obispo 2020 Urban Water Management Plan can be found at:
https://www.slocity.org/home/showpublisheddocument/31041/637673768464130000
5 The 2019 Cal Poly Campus Master Plan can be found at: https://masterplan.calpoly.edu/docs/cal-poly-campus-
master-plan-2019-06-27.pdf
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City of San Luis Obispo Water Conservation and Efficiency Plan P a g e | 11
systems, the City has developed a Water Distribution System Operations Master Plan6, and
conducts annual Water Loss Audits.
Water Sources
The City utilizes three surface water reservoirs to meet its potable water demand. Salinas
Reservoir, located nine miles southeast of the community of Santa Margarita, has provided water
to the City since 1944. Whale Rock Reservoir, located one-half mile east of the town of Cayucos,
has been a water source for the City since 1961. Water deliveries from Nacimiento Reservoir,
located 14 miles northwest of the City of Paso Robles, to the City began in January 2011. Three
distinct raw water transmission facilities deliver water to the City’s WTP from the Salinas, Whale
Rock, and Nacimiento Reservoirs. The City does not currently rely on local groundwater to serve
the community’s long-term water supply needs. However, the City has relied heavily on
groundwater during past droughts and is planning to resume the use of groundwater pumping in
2026. The City is supplied recycled water from its WRRF, which is utilized for landscape irrigation
and for construction water (dust suppression, compaction, etc.). The City will be maximizing the
production of recycled water with the upgrade of the WRRF, currently under construction. Figure
1 shows the location of the City’s reservoirs and raw water conveyance pipelines.
Water Treatment System
The City’s WTP is located on Stenner Creek Road, northwest of the Cal Poly campus. The facility
was constructed in 1964 to provide treatment of surface water from Salinas and Whale Rock
Reservoirs. The WTP is a conventional plant that includes ozone disinfection, coagulation,
flocculation, sedimentation, and filtration. The WTP was originally designed to treat up to eight
million gallons per day (mgd). In 1977, the plant was upgraded to provide 11.5 mgd of treatment
capacity but has been able to treat up to 12.0 mgd for limited periods during peak summertime
water demands. In 1994, the WTP was upgraded to comply with new regulations and to increase
the treatment capacity to 16.0 mgd. In 2020, the City entered into a public/private partnership with
Pacific Gas and Electric (PG&E) for the Water Energy Efficiency Project at the WTP. Project
components included upgrading the ozone generation system, Supervisory Control and Data
Acquisition (SCADA) system, plant service water, and improvements to the Transfer Pump
Station. The implementation of the Water Energy Efficiency Project is estimated to result in a
reduction of energy usage of over 33 percent annually from 2019 WTP operations.
Water Distribution System
The City’s potable water distribution system delivers water from the WTP to approximately 16,500
metered customers and over 2,000 fire hydrants via 190 miles of water mains, ten treated water
storage tanks, and seven pump stations. The water delivered from the WTP is split into two main
distribution networks, the high-pressure side of town and the low-pressure side. The WTP has a
large pump station (the Transfer Pump Station) that pumps water to the high-pressure zones
which provide service to the higher elevation areas in the City. The transfer pumps take
approximately half of the produced water, increase the pressure, and then provide water to
Reservoir #2, Cal Poly, and other portions of the City, generally north and east of the Union Pacific
Railroad tracks. Water flows by gravity directly into the lower pressure zones from the WTP's
6 The City of San Luis Obispo Final Potable Water Distribution System Operations Master Plan, December 2015, can
be found at: https://www.slocity.org/home/showpublisheddocument/6439/636009798150130000
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City of San Luis Obispo Water Conservation and Efficiency Plan P a g e | 12
onsite clear well treated water storage tanks. The City has ten water storage facilities, seven of
which are steel storage tanks ranging in size from 0.04 to 4.0 million gallons and three concrete
facilities with a capacity of 0.35 to 7.5 million gallons. In 2023, the combined storage capacity is
23.705 million gallons. The goal of the distribution system is to provide uninterrupted water flow
at adequate pressures (between 40 pounds per square inch (psi) and 80 psi) to meet all fire and
domestic flow requirements and to minimize system water loss due to breaks and leakage. This
pressure range will meet the needs of most irrigation sprinklers and other uses and provide
adequate pressure for fire sprinkler systems. Preventative maintenance is performed to minimize
water service disruption, prolong system service life, and reduce water loss.
The water distribution team is currently in the process of updating mechanical meters to digital
meters that will allow the City to utilize Advanced Metering Infrastructure (AMI) to read water
meters through a cellular network. This system will provide customers a portal to track their water
use and be alerted of potential water leaks. Automatic reads will also allow the City to eliminate
the need for contract meter reading, identify instances of potential water waste or leaks more
quickly, and improve customer service operations.
Contract Meter Reading
In January 2015, the City executed its first water meter
reading contract to address irregular billing period
lengths and billing dates during the City’s Average
Winter Water Use billing cycle. Meters are read at the
beginning of each month utilizing a contract meter
reading service provider. The use of this service
makes it feasible to have all of the City’s water meters
read in one week and for billing dates to be
standardized for all ratepayers. Contract meter
readers also take pictures of water meter reads that
are outside a normal range of water consumption. Prior
to contract meter reading, Water Resources staff had
to visit a property to re-read a meter if the meter read
appeared outside of a normal range. Staff are now able
to utilize the picture taken by the contract meter reader
to inform customers of the potential for a water leak or
another cause of high consumption. The pictures have
also reduced the number of billing errors related to
misread meters. The City continues to utilize a contract
meter reading service provider in 2023 and looks to
expand the efficiencies gained through use of these
services, and associated technology, in the future.
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3. WATER SUPPLY
AND DEMAND
Water Supply
Water supply reliability is the City’s ability to meet the water needs of its customers under varying
conditions. The City estimates annual Water Supply based on Water and Wastewater
Management Element (WWME), Section 37. This method incorporates Safe Annual Yield from
Salinas and Whale Rock Reservoirs as determined through the City’s 2018 Safe Annual Yield
Model, the City’s contractual amount of water from Nacimiento Reservoir (Dependable Yield), the
prior Calendar Year volume of Recycled Water utilized by the City, and reduction in reservoir
storage caused by siltation as directed in WWME Policy A 4.2.2. As described in Chapter 6 of the
City’s 2020 UWMP8, the City assesses water supply reliability by analyzing the hydrological
variability of the City surface water reservoirs (Salinas, Whale Rock, and Nacimiento), regulatory
variability, climate conditions, and other factors that may affect the City’s water supplies and
customer water uses. This analysis is done using the City’s Water Projection model and applies
worst-case drought conditions according to guidelines set forth in the UWMP plan documentation.
The City accounts for the water supplies necessary to meet community needs using the methods
detailed in WWME Section 5. The amount of water needed to serve the City’s future residential
and non-residential water demand is termed the primary water supply. The primary water supply
is calculated using the build-out population identified in the General Plan, Land Use Element
(2014) and 117 gallons per capita per day (GPCD), which is the maximum allowed per capita
water use under the Water Conservation Act of 2009 (SB X7-7)9.
7 The City of San Luis Obispo General Plan, Water and Wastewater Element is available at:
https://www.slocity.org/home/showdocument?id=6649
8 The City’s 2020 Urban Water Management Plan can be accessed from the California Department of Water
Resources, WUEdata Portal at: https://wuedata.water.ca.gov/uwmp_plans.asp?cmd=2020
9 Senate Bill No. 7 – Water conservation, is available at:
https://leginfo.legislature.ca.gov/faces/billNavClient.xhtml?bill_id=200920107SB7
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City of San Luis Obispo Water Conservation and Efficiency Plan P a g e | 14
Fiscal Year (FY) 2022-2023 (July-June) available water supply was 10,183 acre-feet (AF; Table
2). Results from the City’s Water Projection Model demonstrate that this is a reliable estimate of
supply availability for the Current Year as well as extended drought periods (greater than 10
years).
Table 2. Annual Water Supply for Fiscal Year 2022-23.
Water Source Annual Water
Supply (AF) Description
Nacimiento Reservoir 5,482 Dependable Yield1
Salinas & Whale Rock Reservoirs 4,910 Safe Annual Yield2
Recycled Water 291 2022 Annual Usage3
Siltation from 2010 to 2060 (500) WWME Policy A 4.2.24
Total Availability 10,183 ---
1Dependable Yield is the contractual amount of water the City has rights to from Nacimiento Reservoir.
2The City’s Safe Annual Yield model was updated in 2018.
3The quantity of recycled water included (291 AF) is the actual prior year’s usage (calendar year 2022) per General
Plan Water and Wastewater Management Element Policy A 7.2.2.
4Reservoir siltation is a natural occurrence that reduces storage capacity over long periods, resulting in the reduction
of safe annual yield.
Water Demand
The FY 2023 calculated potable demand was 6,262 AF based on the 2023 population of 47,788
and per-capita daily demand of 117 GPCD. The actual FY 2023 demand shown in Table 3 (4,935
AF) is lower than the estimated demand because of more efficient water use (92 GPCD) and
variations in water needs caused by annual climate variations. The City’s total water demand has
not increased at a rate that follows the rate of population growth (Figure 2). In fact, community-
wide water use has decreased since 1987 when it was at a high of 182 GPCD. The residential
GPCD (R-GPCD) for the City during FY 2023 was 53 R-GPCD, which is considerably lower than
the San Luis Obispo County average of 70 R-GPCD for 2022, according to the California Water
Board’s Water Conservation Reporting10. The FY 2023 non-potable demand was 231 AF. This
represents recycled water used for irrigation which acts to offset potable water use.
10 The California Water Board Water Conservation and Production Reports can be found at:
https://www.waterboards.ca.gov/water_issues/programs/conservation_portal/conservation_reporting.html
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City of San Luis Obispo Water Conservation and Efficiency Plan P a g e | 15
Table 3. Water Supply Use by Source for Fiscal Year 2023.
2023 Fiscal Year Water
Supply Use (AF)1 Percentage of Annual Use
Nacimiento Reservoir 2,096 42%
Whale Rock Reservoir2 1,660 34%
Salinas Reservoir 948 19%
Recycled Water 231 5%
Groundwater 0 0%
Total City Water Demand 4,935 100%
1Values are rounded.
2Water delivered to Cal Poly State University is excluded from the City’s water demand, as Cal Poly has its own water
storage and water diversion rights in Whale Rock Reservoir.
3Groundwater was not used for potable purposes during FY 2022.
Figure 2. Water Demand by Source (FY2000-2022).
Analysis of Water Use by Customer Group
The City has several different customer types, which can primarily be categorized as residential,
commercial industrial and institutional (CII), landscape, and recycled water users. These
categories are then further broken down into classifications based on facility. These classifications
allow the City to better understand specific customer water needs, develop more effective water
conservation programs, and establish fair and equitable water rates.
Residential Water Use
Residential water use is comprised of single-family residences (SFR), multi-family residences
(MFR), mobile home parks, and homestays. As displayed in Table 4, in FY 2023 most of the City’s
potable demand was for SFR use (50%), followed by MFR (17%). During FY 2023, 2,849 AF of
water was utilized by all residential water customers in the City. Residential demands are
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generally greatest during the period May through October when precipitation is generally low, and
temperatures are highest. This suggests that residential demand is driven by outdoor irrigation
during hot, dry periods. During the cooler, winter months when landscape irrigation is minimal,
the R-GPCD can be used as a rough estimate of indoor residential water use; for the City this
value averages about 44 R-GPCD for the period 2015-2022.
Table 4. Water Demand by Customer Category for Fiscal Year 2022-23.
Customer Category Water Demand (AF) Percent of Total
Demand
Single Family Residential 2,072 50%
Multi-Family Residential 704 17%
Commercial 882 21%
Institutional 109 3%
Industrial 34 1%
Dedicated Residential Irrigation Meters 73 2%
Dedicated CII Irrigation Meters 235 6%
Total Potable Water Demand 4,108 100%
Commercial, Industrial, and Institutional (CII) Water Use
CII water use varies based on the type and size of operations, the facility’s water demands
(landscaping and plumbing fixtures), and the water practices in place. The City’s CII customers
are categorized into 28 classifications, which are detailed in the Appendix A1 of this plan. These
classifications allow the City to identify potentially abnormally high-water users within each
classification and to estimate water use of new businesses proposed for development within the
City. CII water demand, not including landscape irrigation demand, accounted for approximately
25% (1,025 AF) of potable water demand during the FY 2023.
Landscape Water Use
Landscape water use is comprised of City Park landscaping, City landscaping (i.e. medians,
parkway, and facility landscaping), residential landscaping, and CII landscaping. The City’s
municipal code requires that nonresidential, multifamily, or mixed-use properties with one
thousand square feet of landscaping or greater use a dedicated irrigation meter (DIM) to measure
landscape irrigation demand11. DIMs allow customers to more precisely understand water used
for landscaping and identify leaks or other issues associated solely with the irrigation system. This
allows property owners to make more informed decision about their overall water consumption
and can assist in efficient water use. Additionally, forthcoming regulations from the State of
California will require the use of DIMs on certain CII properties, and the City’s policy requiring
DIMs positions it well to meet those regulations. About 235 AF of water was measured by DIMs
at CII properties in the City in FY 2023. This is approximately 6% of the City’s potable water use
for that year.
Recycled Water Use
The primary use of recycled water in the City is for landscape irrigation with the majority of that
use occurring from May through October. About 231 AF of recycled water was used for landscape
11 City municipal code 13.04.130, Water Meters is available at:
https://sanluisobispo.municipal.codes/Code/13.04.130
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irrigation in FY 2023. Of this amount 45% was utilized to maintain City landscape areas, including
parks, 23% for MFR landscaping, and 32% for CII landscaping and private parks. About 26 AF of
recycled water was used for construction water in FY 2023. The City has identified a “seasonal
surplus” of recycled water available in excess of the required discharge to San Luis Obispo Creek
(5 AF per day as required by the National Oceanic and Atmospheric Association, National Marine
Fisheries Service in 2005) and recycled water for landscape irrigation and construction needs. As
only a limited amount of landscape irrigation takes place from November to April (seasonal off-
peak period), more than 6 AF per day of recycled water is available during the seasonal off-peak
period. An upgrade of the WRRF is underway, which will accommodate the City’s buildout and
maximize recycled water production. The upgrade will enable the City to maximize beneficial use
of recycled water, including consideration of either direct or indirect potable reuse in the future.
Until potable reuse is implemented, the City is focused on expanding the use of recycled water
within City limits to help offset potable water use. Per the City’s Recycled Water Master Plan,
recycled water use is projected to increase by 10 AF per year.
Conservation as a Source of Supply
Water conservation above and beyond the state’s regulations can be considered a source of
water supply because the City retains that volume of water in its reservoirs and groundwater
aquifers for future use. Per SB X7-7, the City is required to meet a per-capita target of 117 GPCD.
Prior to FY 2010 the City exceeded the water conservation target; per capita water use for the
City was 129 GPCD in FY 2007 and FY 2008 (Figure 3). Since FY 2010 the City is consistently
below the SB X7-7 target and the water conservation mandates enacted by the State during the
2015-2017 drought reduced the City’s annual demand to its current levels of around 100 GPCD,
while current water conservation efforts are aimed at maintaining or reducing per-capita water
use. Average annual water supply resulting from water conservation for FY 2010-2023 is 813
AFY, or about 20 percent of the City’s FY 2023 potable demand.
The City accounts for the increase in available water supply resulting from water conservation by
including it in its water supply accounting. In addition to the Primary Water Supply described
above, the City estimates a Reliability Reserve and a Secondary Water Supply. The Reliability
Reserve acts as a buffer for unforeseen or unpredictable long-term impacts and the water supply
that exceeds the City’s Primary Water and Reliability Reserve is referred to as the City’s
Secondary Supply.
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Figure 3. Actual City Water Demand Versus SB X7-7 Estimated Water Demand (FY 2000 - FY 2023).
Impact of Plumbing Code or Building Code on Water Use
Plumbing and building codes serve as instrumental tools for water conservation efforts. These
type of conservation efforts are considered “passive” and result in long-term, reliable water
savings as old inefficient fixtures are replaced over time. Federal and state policies such as the
Federal Energy Policy Act of 199212, the California Code of Regulations Title 2013, and the
California Code of Regulations, Title 24, California Green Building Standards Code (CALGreen
Code)14 mandate fixtures being sold or installed meet specific water efficiency standards. These
include low-flow toilets, urinals, showerheads, faucets, and pre-rinse spray valves, which are
designed to limit water usage without compromising performance. City of San Luis Obispo
plumbing codes also mandate the use of water-efficient fixtures and designs, aligning with
statewide plumbing codes and water conservation initiatives.
The City adopted Chapter 17.70.220 Water-efficient landscape standards15 as a part of its
municipal code that promotes the use of native and drought tolerant materials and sets water
efficient landscape standards consistent with State law. Systems must be designed for efficient,
12 The Federal Energy Policy Act of 1992 can be accessed at: https://afdc.energy.gov/files/pdfs/2527.pdf
13 The California Code of Regulations, Title 20. Public Utilities and Energy can be accessed at:
https://www.energy.ca.gov/sites/default/files/2021-07/Title%2020%20Updated%20July%2023%2C%202021.pdf
14 The California Code of Regulations, Title 24, California Green Building Standards Code (CALGreen Code) can be
found at: https://codes.iccsafe.org/content/CABC2022P1/california-code-of-regulations-title-24
15 City of San Luis Obispo municipal code 17.70.220, Water-efficient landscape standards is available at:
https://sanluisobispo.municipal.codes/Code/17.70.220
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City of San Luis Obispo Water Conservation and Efficiency Plan P a g e | 19
conservative use of water that are in accordance with the City’s Engineering Standards16.
Community Design Guidelines17 also required proposed landscaping to set goals to reflect the
local climate and conserve water, including considering water shortages, effects of drought, plant
loss, and increased water cost. Proposed developments must also incorporate features such as
permeable surfaces that facilitate the absorption of water into the ground as a part of the City’s
Community Design Guidelines. Mandating water-efficient fixtures and optimizing outdoor water
use create a foundation for sustainable water practices that create long-term water savings.
Overall Supply and Demand Balance
Per California Water Code (CWC §10632.1.)18 the City conducts an Annual Water Supply and
Demand Assessment (Water Supply Assessment) for the purpose of (i) evaluating its water
supply reliability for the current year and one subsequent dry year and (ii) generating and
submitting an Annual Shortage Report to the California Department of Water Resources. The City
converts annual supply and demand values to monthly volumes for the purposes of this Water
Supply Assessment so that potential seasonal water shortages are highlighted. Monthly supply
and demand volumes are calculated using average monthly demand as a percent of average
annual historical demand for the period following the previous drought (2015-2017) and including
the most recent drought. These monthly average demand percentages are then applied to the
annual supply and demand to provide monthly volumes. The City’s FY 2022 Water Supply and
Demand Assessment showed that the City consistently has a water surplus (supply is greater
than demand) month to month for a typical year and also a subsequent, hypothetical dry year.
For longer-range estimations of supply and demand balance the City utilizes a Water Projection
Model to test both hypothetical and actual water demand scenarios and to forecast how long
water supplies will sustain the community under specific conditions. The Water Projection Model
accounts for the storage in the City’s surface water reservoirs, in conjunction with other available
resources (i.e., groundwater and recycled water), needed to meet the City’s water demand. The
model uses historical hydrologic information (rainfall, evaporation, inflow) based on the average
for the worst drought period (2012 to 2014). Other data included in the model are:
• Water entitlement
• Current reservoir levels/storage
• Average GPCD community water demand
• Rainfall
• Temperature
• Evaporation
• Existing population
• Estimated population growth
16 Standard Specifications & Engineering Standards August 2020:
https://www.slocity.org/home/showpublisheddocument/27919/637341402080900000
17 San Luis Obispo Community Design Guidelines:
https://www.slocity.org/home/showpublisheddocument/2104/635491488007630000
18 Cal. Water Code §10632.1. can be accessed at:
https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=WAT§ionNum=10632
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The City uses the Water Projection Model to study the potential impacts of various intensities of
drought conditions, including increased air temperature and evaporation rates, along with
decreased precipitation. Utilizing the Water Projection Model as part of its water supply
management strategy, the City can foresee whether a water supply shortage is anticipated in any
given year and the severity of a shortage based on the availability of the City’s different sources
of supply and water demand trends. When utilizing the Water Projection Model to estimate future
water supply and demand, GPCD decreases in accordance with the 2020 WSCP. For example,
water demand is calculated using an initial value of 117 GPCD and decreases by ten percent
(corresponding to a ten-percent decrease in water use) to 105 GPCD when available supply is
less than 5-years of estimated annual demand. This ten percent reduction is in alignment with the
demand reduction that the City projects it would achieve from water conservation measures
outlined in the WSCP. Model results using FY 2022 data showed that the City would have
adequate supply to meet City demands without implementing the WSCP for ten years of
continuous drought conditions (Figure 4).
Figure 4. Historical Storage Volume, in Acre-Feet, in Salinas and Whale Rock Reservoirs, and Projected
Storage Volume Through an Extended Drought Period.
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Water Shortage Contingency Plan
The City adopted the 2020 WSCP on June 15, 202119. The City’s WSCP provides the foundation
for a staged response to worsening water shortage conditions. A water shortage could occur due
to drought, earthquake, infrastructure failure, or another emergency. Drought may occur with
unpredictable frequency, intensity, and duration. An update to the City’s Water Conservation
Ordinance (Chapter 13.07 of the Municipal Code), established the regulations and procedures for
implementing this Plan and updated the ordinance to comply with newer requirements under
Water Code Chapter 3.3: Excessive Residential Water Use During Drought.
The City’s water shortage response is dependent on the ability to temporarily augment supply
and/or reduce water demand. The City’s water shortage response would combine a variety of
strategies including outreach, indoor water efficiency regulations, and outdoor irrigation
restrictions, each increasing in intensity as the shortage persists and the City’s water supplies are
further restricted. Implementation of these restrictions is necessary to conserve the City’s water
supply for the greatest public benefit regarding domestic use, sanitation, and fire protection. It is
the City’s goal to implement water demand reduction programs that will achieve measurable water
savings without requiring customers to make significant lifestyle changes. In the more advanced
water shortage stages lifestyle and water-use habit changes will be necessary.
The City’s WSCP consists of seven stages. The multi‐stage approach provides different levels of
response for a water shortage event ranging from a ten percent supply deficiency up to a 50
percent or greater deficiency. The purpose of establishing water shortage stages is to clearly
define the severity of the shortage and establish appropriate targets for demand reductions.
Defining these stages allows the City to respond to worsening conditions, with each stage
“triggering” different actions. City Council may adopt variations of these Water Shortage
Response Actions, independent from the stage resulting from the use of the Water Projection
Model, to strategically address the current water shortage situation.
19 The City’s 2020 Water Shortage Contingency Plan can be accessed at:
https://www.slocity.org/home/showpublisheddocument/31039/637673766931570000
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4. HISTORICAL AND
CURRENT WATER
CONSERVATION
PROGRAM
Water conservation is an integral part of the City’s overall water management strategy and was
first referenced as a part of the City’s water management policies in 1973. In 1985, the City
adopted the Annual Water Operational Plan policy that established water conservation as a
means of extending water supplies during projected water shortages. Many technological and
philosophical changes have occurred since that time, proving that water conservation can be used
for both a short-term corrective measure to address immediate water supply shortages, and as a
long-term solution to water supply reliability.
The City’s water conservation program aims to implement water conservation measures that
optimize water supply, treatment, and delivery requirements to assist with the long-term
sustainability of water resources. Water conservation measures are those programs and
incentives that prevent the waste of water and promote the reasonable and efficient use and reuse
of available supplies. These water conservation measures also allow the City to continue to
achieve compliance with all state water reduction and efficiency regulations. The following
provides a summary of the City’s current and historical water conservation efforts broken down
into operational (internal facing) and external (customer oriented) water conservation programs.
Water conservation programs the City has implemented due to State or Federal requirements are
outlined in the Regulatory Compliance section of this plan (Section 5).
Operational Programs
Operational programs encompass the programs and policies in place that prevent water waste,
reduce water loss, and address water efficiency within the City’s water service operations
internally. By implementing and adhering to these programs, the City aims to establish a
sustainable water service system that not only conserves water but also decreases operational
costs and fosters long-term environmental stewardship.
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Metering and Billing
In accordance with the 2020 UWMP guidebook20 and CWC § 527 (2022)21, the City has
implemented universal metering of all service (public and private) connections. Metering service
connections encourages water conservation by effectively billing customers for the quantity of
water consumed, forming a relationship between water consumed and the total cost of the water
bill. The City also meters all water supply sources, including the City’s three primary water
sources, groundwater, and recycled water sources. Having a fully metered system allows the City
to effectively monitor and analyze where water losses are occurring and where additional water
savings may be possible. The City continues to implement effective metering requirements for
new developments by requiring separate water meters for residential, non-residential, and
landscape use and is in the process of upgrading all water meters to digital water meters to deploy
AMI in the future.
In addition to metering water consumption, the City’s water and wastewater rates are set to
promote water conservation practices. All meters within the City are read and billed monthly and
the City’s Utility Billing team performs routine billing audits to reduce data handling errors.
Although meters are read and customers are billed in hundred cubic feet (HCF), customers are
provided conversion factors on both paper and online bills to convert consumption into gallons.
The City also provides sanitary sewer collection and treatment service for the community. Sewer
rates for residential customers are based on the volume of metered water used each month and
are set using wintertime water use. If in the event a meter cannot be read, for example due to
repairs, or is not registering the City may estimate usage based on historical customer usage.
However, the City makes every effort to avoid estimating reading and attempts to limit estimated
readings to no more than twice per year per customer. Details on how estimations are computed
are outlined in Section 13.04.13022 of the City’s Municipal Code.
Water Loss Control Program
The City has been conducting annual American Water Works Association (AWWA) water loss
audits since 2009 to identify and work towards reducing real and apparent losses within the
distribution system. Water loss performance indicators identified from the 2016 – 2021 AWWA
water loss audits are shown in Table 5 below. These water loss audits are prepared using the
AWWA/IWA Water Audit Method, as described in the AWWA Manual of Water Supply Practices
– M36, Water Audits and Loss Control Programs, and is validated by a certified Level 1 Water
Audit Validator each year. To provide transparency and accountability, these audits are made
available to the public on the City’s website23.
20 The Urban Water Management Plan Guidebook 2020 is available at: https://water.ca.gov/-/media/DWR-
Website/Web-Pages/Programs/Water-Use-And-Efficiency/Urban-Water-Use-Efficiency/Urban-Water-
Management-Plans/Final-2020-UWMP-Guidebook/UWMP-Guidebook-2020---Final-032921.pdf
21 2022 California Water Code, Section 527 is available at: https://law.justia.com/codes/california/2022/code-
wat/division-1/chapter-8/article-3-5/section-527/
22 The City of San Luis Obispo municipal code 13.04.130, Water meters is available at:
https://sanluisobispo.municipal.codes/Code/13.04.130
23 The city’s Water Loss Audits from 2016 through 2021 can be accessed at:
https://www.slocity.org/government/department-directory/utilities-department/documents-and-files
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City of San Luis Obispo Water Conservation and Efficiency Plan P a g e | 24
Table 5. Key Water Loss Audit Metrics.
2016 2017 2018 2019 2020 2021
Apparent Losses (gal/conn/day) 8.34 12.62 8.99 6.25 6.33 6.28
Real Losses (gal/conn/day) 33.51 32.65 16.00 13.54 15.47 23.57
Non-Revenue Water as a Percent
of Cost of Operating System 2.8% 3.3% 2.3% 2.2% 2.8% 3.5%
Infrastructure Leakage Index (ILI)1 2.02 1.96 0.97 0.93 1.06 1.60
1. The Infrastructure Leakage Index (ILI) is a ratio of the Real Losses to the Unavoidable Real Losses. This
performance indicator is dimensionless. In California, the median ILI is 1.4.24
To further reduce water loss, the City conducts water service line replacement projects based on
service line age and condition, along with extensive programs to replace defective polybutylene
service lines that have been identified to have a high likelihood of failure. Water meter
replacement programs exist to replace meters based on age, consequence of failure, and
likelihood of failure. Along with these maintenance programs, the City also implements a valve
exercising program that ensures water mains can be isolated during repairs to minimize the
amount of water lost during water main breaks and repairs.
In 2015, the City completed its Potable Water Distribution System Operations Master Plan25 which
identifies and prioritizes best practices, actions, and goals regarding future maintenance and
capital improvement projects to help reduce future water loss due to infrastructure failure. That
work effort included development of a comprehensive hydraulic model of the City’s water
distribution system. The hydraulic model is used to determine available service pressure and is
maintained annually to remain current with the waterline replacement project, new water main
installations, zone consolidations, and other projects. In 2019, the City began using acoustic
correlation equipment where acoustic sensors are attached to water valves to measure the speed
at which sounds waves travel along the pipe. These sensors effectively listen to water flowing
through the pipe and can detect when water is escaping through a leak. The location can then be
pinpointed within about two feet, which helps reduce excavation costs. Using this tool regularly,
the City can more accurately locate small leaks, resulting in less damage to surrounding
infrastructure, further optimize its capital spending, minimize water main breaks, water loss, and
damage from leaks, and better manage aging water infrastructure. Moving forward, the City plans
to continue to work to reduce real and apparent water losses by replacing aging infrastructure to
prevent pipe breaks and leaks, implementing a comprehensive meter testing and calibration
program to ensure water meters are functioning per manufacturers’ specifications, and continuing
with its comprehensive meter replacement strategy to ensure water used at homes and
businesses is correctly recorded.
Recycled Water Program
The City of San Luis Obispo has been utilizing recycled water as a component of its multi-source
water supply since 2006. Recycled water acts as a means of water conservation by offsetting
usage that would have otherwise utilized the City’s potable (drinking water) supply. Additionally,
because recycled water is reliant on wastewater flows, and therefore less dependent on weather
24 The California Department of Water Resources Water Loss Audit Reports and associated data for calendar years
2016 to present can be found at: https://wuedata.water.ca.gov/
25 The City of San Luis Obispo Final Potable Water Distribution System Operations Master Plan, December 2015,
can be found at: https://www.slocity.org/home/showpublisheddocument/6439/636009798150130000
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than the City’s surface water reservoirs, recycled water helps to diversify the City’s water supply
portfolio and acts as an alternative, reliable water supply during times of drought.
Currently there are 54 recycled water sites
throughout the City. Each site is required to
have a site supervisor, which must undergo a
site supervisor training and complete quarterly
reports including identifying water waste runoff
and system deficiencies. Site supervisors are
either property owners, property managers, or
landscape maintenance professionals.
Although recycled water is often not subject to
water efficiency ordinances and state-
mandated reduction requirements, droughts
across the State, and specifically in the Central
Coast region, have contribute to a heightened
interest in the City’s recycled water supply over
the years. Improvements in water conservation
or changes in use, such as potable reuse,
would impact how recycled water is used
throughout the City. Additional information regarding the City’s recycled water program can be
found in the City’s 2017 Recycled Water Master Plan26.
External Programs
External, customer-facing programs are instrumental in engaging the community and promoting
water conservation practices beyond the City's water service operations. These programs are
designed to educate and encourage customers to play an active role in preserving water
resources and adopting sustainable water use practices. By implementing these programs, the
City aims to empower its residents and businesses to make informed choices that contribute to a
more water-conscious community and cultivate a culture of responsible water consumption.
Water Use Reports and Audits
The City’s Water Resources section offers no-cost assistance to both residential and non-
residential customers who have high water use or would like to reduce their water consumption.
Water resource technicians examine historical water use and the property with the customer to
identify potential water saving opportunities and provide information about irrigation reduction
methods, proper property maintenance, confirm meter functionality, water leak determination, low
flow fixtures installation, and general information on methods for reducing water use. This service
is often offered proactively to customers who have unexplained high use, water waste violations,
or other instances where a review could provide potential water savings. However, customers
may also request assistance at any time. To maximize staff time and resources, staff first attempt
to work with customers over the phone or via email. If staff are not able to contact a customer,
they will conduct a site visit and either make contact in person or leave a door hanger. Customers
26 The City of San Luis Obispo 2017 Recycled Water Master Plan is available at:
https://www.slocity.org/home/showpublisheddocument/14955/636269147657570000
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are also provided a copy of the City’s Water Audit Worksheet27 to conduct a more in-depth
analysis of indoor and outdoor daily water use. In the future, the program may be expanded to
include more in-depth leak detection methods (i.e. acoustic listening devices) and irrigation audits.
Complimentary Devices and Financial Incentives
The City provides various water conservation devices as a complimentary service to the
community. Currently, the program provides low-flow showerheads, faucet aerators, flow meter
bags, five-minute shower timers, dish squeegees, leak detection dye tablets, hose nozzles, soil
moisture meters, save water posters, and lawn signs. Customers are encouraged to notify the
City if there are items they are interested in that are not currently made available as part of the
program. Staff will continue to stock and promote the use of these and other complimentary items
as funding allows.
The City has also provided various rebates for water conservation devices and actions over the
years. A rebate is a partial refund after a customer has purchased a water-efficient device to
incentivize customers to purchase a water-efficient device over a less efficient device. During the
drought in 2015, the City Council authorized $100,000 in support of effective rebate programs.
Rebate of $100 dollar were provided for qualified toilet and washing machine replacements. City
Council authorized $30,000 in 2022 to launch an updated rebate program. Beginning in 2023, the
City now offers rebates for high-efficiency toilets and urinals, large landscape smart irrigation
controllers, and water-efficient restaurant dipper wells. Current rebate funding is equitably
allocated between SFR, MFR, and CII account holders, ensuring the program does not favor one
customer class. Should funding not be exhausted by one customer class type, staff will reevaluate
allocating funds to other customer class types, should those classes have fully exhausted their
own allocated funds. Lastly, the City has also entered into a partnership with Rachio through the
California Water Efficiency Partnership to offer discounted smart irrigation controllers to single
family residences. Offering rebates and discounted smart irrigation controllers assist customers
to modify their irrigation systems to be more efficient and apply water in a more efficient manner.
27 The City of San Luis Obispo Water Audit Worksheet is available at:
https://www.slocity.org/home/showpublisheddocument/30756/637883714862000000
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Public Information and Outreach Programs
The City has used public education and outreach as a mechanism for decreasing water use in
the City and for promoting water conservation since the 1970s. Public education is often a
component of water conservation programs aimed at encouraging customers to proactively
decrease water usage and participate in conservation rebates and programs. Staff routinely
update and maintain the City’s water conservation website, release city news articles and e-
notifications, participate in local events such as farmers markets, community events, and local
career fairs, host community tours at Whale Rock Reservoir, the WTP, and the WRRF, provide
informational brochures and printed newsletters, and create social media campaigns (Facebook,
Instagram, YouTube, and LinkedIn), and paid radio advertising. Additional public outreach and
education programs have
included informational
welcome emails, “We’ve Let it
Go, California Gold” landscape
signs deployed during the
drought on turf areas the City
maintains, billing inserts, “how
to” videos, direct mail
campaigns, and meetings with
local business groups and
homeowners associations. The
City is committed to reviewing
and modifying the public
education and outreach
program to ensure that
messaging stays effective and
relevant. For example, in 2021,
the City launched an interactive
street sticker campaign, where
residents and visitors could
scan QR codes on various infrastructure locations in order to access an interactive, virtual ArcGIS
Storymap28 of the City’s water and wastewater resources and infrastructure. In 2022, staff
launched a Water-Wise Landscape of the Month competition where residents could submit their
yard or nominate neighbors’ yards that embrace water-wise landscaping techniques; helping to
encourage residents to conduct landscape transformations that adopt climate-appropriate native
plants that require little to no supplemental irrigation. Moving forward staff are working to create
virtual reality (VR) tours and educational games to educate a wider audience and utilize new,
interactive outreach methods.
The City has also been a long time member of the San Luis Obispo Partners in Water
Conservation, a joint regional effort between local water purveyors in San Luis Obispo County, to
promote and collaborate on water conservation and efficiency measures. Participation helps
facilitate regional knowledge sharing and educational programs. Most notably, the partnership co-
28 The City of San Luis Obispo ArcGIS storymap Get to know YOUR water can be accessed at:
www.slocity.org/yourwater
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funded and launched the SLO Water Wise Landscaping website29, which provides design and
installation resources for water-wise landscaping that are specific to microclimates in San Luis
Obispo County. The guide provides information on how customers can irrigate based on plant
needs and discourages customers from over watering, watering too frequently, or watering during
the times of the day when water loss to evaporation and wind is greatest. In addition to the SLO
Water Wise Landscaping website, the City also provides information on how customers can find
certified water efficient landscape contactors, designers, landscapers, or irrigation auditors on its
website.
Children’s Specific Outreach
In addition to general outreach,
the City has also had a long
standing history of working to
instill water awareness in
children to help further promote
households to participate in
water conservation and set the
stage for students to make
informed and appropriate
decisions about water later in
life. The City provides education
programs on various water
related topics for San Luis
Obispo Coastal Unified School
District schools within the city.
The spotlight program, The Story
of Your Water, teaches third
through fifth graders about the
water cycle, water treatment
process, water use, water
conservation, and water
reclamation. At the end of the
program students are provided a
flow meter bag and toilet leak
detection tablets to promote
discussing water conservation
at home and identifying if their
home has a leaking toilet or
fixtures that can be updated to
low-flow. In addition to classes,
the City has hosted art contest
and offers tours of the WTP and
WRRF.
29 Waterwise Landscaping for San Luis Obispo County website is available at:
https://www.slowaterwiselandscaping.com/
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5. REGULATORY
COMPLIANCE
California has enacted regulations to promote water
conservation and sustainable water management that the
City’s Water Conservation Programs and Water
Conservation and Efficiency Plan must consider.
Historically, some of the most important regulations for
water conservation in California have included the Soil and
Water Resources Conservation Act of 197730, which
requires urban water suppliers to develop and implement
water conservation plans, and the SB X7-731, which
requires urban water suppliers to establish water
conservation targets and report progress toward meeting
those targets. Senate Bill 606 (SB 606)32 and Assembly Bill
1668 (AB 1668)33 are the most recent water conservation
regulations and establish the Long-Term Framework
legislation for making water conservation a California way
30 The Soil and Water Resources Conservation Act of 1977 can be found at:
https://www.congress.gov/95/statute/STATUTE-91/STATUTE-91-Pg1407.pdf
31 California Water Conservation Act, Water Code Section 10608.28(b) provides methods for calculating urban
water use targets that identify per capita use targets that cumulatively result in a statewide 20 percent
reduction: https://california.public.law/codes/ca_water_code_section_10608.20
32 California Senate Bil No. 606, Water management planning is available at:
https://leginfo.legislature.ca.gov/faces/billTextClient.xhtml?bill_id=201720180SB606
33 California Assembly Bill No. 1668, Water management planning is available at:
https://leginfo.legislature.ca.gov/faces/billTextClient.xhtml?bill_id=201720180AB1668&search_keywords=55+gall
ons+water
Making Water
Conservation a California
Way of Life Framework
In 2018, the California State
Legislature passed Assembly Bill
1668 (Friedman, 2018) and Senate
Bill 606 (Hertzberg, 2018) which
directed the State Water Board to
adopt standards for using water
more efficiently.
As part of the proposed regulation,
Urban Retail Water Suppliers,
including the City of San Luis
Obispo, will be held to new “urban
water use objectives” comprised of
indoor residential water use, outdoor
residential water use, commercial,
industrial, and institutional (CII)
irrigation with dedicated meters,
water loss, and unique local uses.
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City of San Luis Obispo Water Conservation and Efficiency Plan P a g e | 30
of life. This framework establishes standards for water use efficiency and requires local water
agencies to set water budgets based on those standards.
Regulatory Programs
Regulatory approaches can be an effective strategy for water suppliers to reduce water use at
the service level. In addition to the regulations the City must comply with at the state level, the
City of San Luis Obispo has also adopted local regulations that prohibit water waste and require
water-efficient plumbing. Below are the current water conservation programs the City has
implemented. The City aims to adopt water-efficient codes and standards that are feasible and
appropriate to the community.
Water Conservation Regulations
Chapter 13.07 of the City’s municipal code, adopted in 1987, outlines water conservation
regulations for the City. Under this code, water waste due to substandard, leaky, or faulting water
fixtures and water waste due to excessive application are prohibited. City staff conduct routine
patrols to monitor water waste and follow set timelines and procedures to ensure community
members are addressing water leaks in a timely manner. In addition to these restrictions,
restaurants may not serve water to customers except upon request and potable water cannot be
used for major construction activities or to wash down sidewalks, driveways or parking areas
except to alleviate fire and sanitation hazards.
Plumbing Retrofit Program
In 1992 the City also adopted plumbing retrofit regulations which require all existing residential
and CII structures to be retrofitted, if not already equipped with, low water use plumbing fixtures
upon sale, change of use, or expansion of use of the property. New developments are required
to comply with CALGreen Code34, which are more restrictive than the City’s Municipal Code.
Plumbing codes and standards are considered a “passive” water conservation measure that
create permanent water-saving potential given a nominal decline in water saving performance
over the useful life of a fixture or appliance.
The City’s plumbing retrofit verification program was most recently amended on December 7,
2021, to require all indoor toilets, faucets, showerheads, and urinals meet the requirements set
forth in California Civil Code CIV § 1101.335. City staff will continue to manage the program and
document compliance within the City. All properties that have been certified to have low-flow
fixtures are shown via a user-friendly online mapping tool at slowater.org, shown below in Figure
5. This tool also provides the City with a database that can be used to help project the
effectiveness of future indoor water fixture rebate, offset, and replacement programs. Water
savings from plumbing retrofits is dependent on the number and current water use of existing
fixtures; however, this program, along with fixture replacement through various rebate programs,
has reduced the City’s long-term water demand by an estimated 1,500 AFY.
34 The California Code of Regulations, Title 24, California Green Building Standards Code (CALGreen Code) can be
found at: https://codes.iccsafe.org/content/CABC2022P1/california-code-of-regulations-title-24
35 California Civil Code, Article 1.4. Installation of Water Use Efficiency Improvements can be found at:
https://leginfo.legislature.ca.gov/faces/codes_displayText.xhtml?lawCode=CIV&division=2.&title=4.&part=4.&cha
pter=2.&article=1.4.
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City of San Luis Obispo Water Conservation and Efficiency Plan P a g e | 31
Figure 5. Screenshot of the City of San Luis Obispo's Plumbing Retrofit Portal.
Water Efficient Landscaping Requirements
The California Department of Water Resources first established the Model Water Efficiency
Landscape Ordinance (MWELO)36 in 1993 and requires local jurisdictions to adopt the state’s
framework or develop alternative water-efficient landscape ordinances that are at least as
effective. MWELO sets guidelines for water budgets, irrigation efficiency, plant selection, and
other factors to encourage sustainable landscaping practices and reduce water consumption in
outdoor spaces. The Utilities Department and Community Development Departments work
together to implement these and other water efficiency standards into land-use planning to
influence water demand within the community. The water efficiency standards require water
efficient design, installation, and maintenance practices to maximize water applied to landscapes
on new and rehabilitated landscapes in both residential and commercial settings. It has been
estimated that landscapes adhering to MWELO landscape irrigation regulations use 80 percent
less water than traditional landscapes.
Future Regulatory Requirements
The City will continue to comply with water conservation related regulations as they are enacted.
Currently, the most notably are the future Urban Water Use Objectives (UWUO) set by the Making
Water Conservation a California Way of Life Framework. The objectives will include standards for
residential outdoor water use, residential indoor water use, CII-DIM outdoor water use, real water
loss, variances, and potential bonus incentives. The sum of each respective standard establishes
an overall water budget, known as the UWUO, which water suppliers cannot exceed on an annual
basis. The City and other water suppliers will be required to meet their overall UWUO and not
standards for each specific category.
36 Information on the California Department of Water Resources, Model Water Efficient Landscape Ordinance can
be found at: https://water.ca.gov/Programs/Water-Use-And-Efficiency/Urban-Water-Use-Efficiency/Model-Water-
Efficient-Landscape-Ordinance
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City of San Luis Obispo Water Conservation and Efficiency Plan P a g e | 32
Through the City’s water conservation programs and policies, water demand over the five-year
period between 2016 - 2022 ranged from a high of 97 GPCD in 2017 to a low of 88 GPCD in
2016, as shown in Figure 6, which are below the City’s SB X7-7 compliance goal of 117 GPCD.
The City’s indoor R-GPCD from 2015-2022 averages around 44. California Department of Water
Resource’s recommended Indoor Residential Water Use Standards are 55 R-GPCD for the years
2020 - 2025, 47 R-GPCD for the years 2025-2030, and 42 R-GPCD beyond 2030. With the
continuation of the water conservation measures listed in this plan, the City anticipates ongoing
compliance with these mandates into the future.
Figure 6. City of San Luis Obispo Annual Per Capita Water Use (in gallons per capita per day, GPCD)
Versus Population and the Target Per Capita Use as Determined by SB X7-7, 2000-2022.
Page 146 of 555
6. EVALUATION OF
LONG-TERM
WATER
CONSERVATION
MEASURES
Water conservation measures were evaluated using the AWE Water Conservation Tracking
Tool37, which evaluates the water savings and program costs of different water conservation
measures for the development of long-range water conservation plans. The model estimates
annual demand reduction in AF, which is divided into active and passive demand reduction for
the model period. Active demand reduction is the share of estimated water savings that can be
attributed solely to the implementation of the conservation program. Passive demand reduction
is the estimated share of water savings that would have been generated in the absence of the
conservation program by (1) plumbing and energy codes interacting with the natural replacement
of toilets, showerheads, and other water-using appliances whose current or future minimum
efficiency is dictated by national, state, or local code requirements plus (2) water savings from
program freeriders – a participant that would have taken the same water-conserving action in the
same timeframe had the program not existed.
The analysis for this plan was conducted in a staged approach to provide an understanding of
benefits and costs of a large, comprehensive conservation program (Plan A); benefits and costs
of a conservation program targeted at the greatest benefit-cost ratio, regardless of budget
restrictions (Plan B); and benefits and costs of a conservation program that provides the greatest
benefit-cost ratio within a budget that is representative of the Utilities Department’s existing
budget (Plan C). The results of the Water Conservation Tracking Tool for each plan are included
37 Alliance for Water Efficiency (AWE) Water Conservation Tracking Tool can be accessed at:
https://www.allianceforwaterefficiency.org/resources/topic/water -conservation-tracking-tool
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City of San Luis Obispo Water Conservation and Efficiency Plan P a g e | 34
in the Appendix of this report and described in the text below. The water conservation measures
included in Plan A represent water conservation measures that Utilities Department Staff have
identified as practical for staff to implement and administer as stand-alone work efforts, and do
not include all possible water conservation measures. The water conservation measures included
in Plan B are a subset of Plan A, and the water conservation measures in Plan C are a subset of
Plan B. All of the conservation program plans assume an initial 2-year period of rebate
implementation for larger water conservation measures such as turf replacement and clothes
washers, followed by an annual implementation of other water conservation measures such as
SFR home water reports, MFR water use audits, and showerhead replacement rebates.
Plan A
Conservation program Plan A is a large, comprehensive conservation program that consists of
29 water conservation measures. Utilities Department staff selected water conservation
measures that staff would be able to implement and administer as stand-alone work efforts;
therefore, implementation of the Plan in its entirety would be impractical for the existing staff and
under the existing budget. Plan A serves to provide an upper threshold for water savings and
program costs in comparison to subsequent, more targeted conservation program plans. Plan A
also serves to estimate the benefit-cost ratios for a large suite of water conservation measures.
These benefit-cost ratios were the basis for determining which water conservation measures
should be included in subsequent conservation program plans.
Plan B
Conservation program Plan B consists of the water conservation measures from Plan A with the
greatest benefit-cost ratios. There are 16 water conservation measures included in Plan B.
Traditional water conservation measures including turf replacement rebates, graywater rebates,
rain barrel rebates, and clothes washer rebates were determined to have a low benefit-cost ratio
in Plan A and were therefore excluded from Plan B. As such, a comparison of benefits and costs
between Plan A and Plan B illustrates the value of implementing water conservation measures
with high benefit-costs ratios. Plan B represents a conservation program plan that could be
implemented and administered with a substantial increase in staff, funding, and resources.
Plan C
Conservation program Plan C utilized the information gained from Plan A and Plan B, as well as
results from a community-wide survey of local businesses, to develop an informed conservation
program that implements high benefit-cost ratio measures within a budget that is representative
of the Utilities Department’s existing budget. There are 12 conservation measures included in
Plan C.
The survey, completed by 240 San Luis Obispo business owners and managers in the fall of
2022, found that over half of those that responded (53.96%) were most interested in a rebate for
WaterSense® high-efficiency toilets. This is believed to be in part because 26% of the
respondents (62 individuals) identified themselves as operating a real estate or property
management business and toilets were the primary water conservation measure that would apply
to this type of business. The interest for all items included in the survey are summarized in Error!
Reference source not found. Additional water conservation measures participants listed as
being of interest included: trees for shading, rainwater retention, compressed air for removing
food residue, AMI and leak detection technologies, rain barrels, pipe replacement, landscape/turf
conversions, native plants, promotion of low-water use businesses such as retail, rate increases,
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City of San Luis Obispo Water Conservation and Efficiency Plan P a g e | 35
and high-efficiency reverse osmosis systems. Ultimately the quantity of those that expressed
interested in items identified as having a high benefit-cost ratio were utilized to estimate the
quantities of the water conservation measures modeled in Plan C.
Table 6. Results of the 2022 Survey of Businesses' Interests in Water Conservation Measures.
Conservation
Measure Yes No Yes, If Increased1
ConserveWell®
Dipper Well 3.23% (7) 93.09% (202) 3.69% (8)
WaterSense High-
Efficiency Toilet 35.12% (72) 52.20% (107) 12.68% (26)
Waterless or High-
Efficiency Urinal 10.10% (20) 86.36% (171) 3.54% (7)
Commercial
Clothes Washer 15.10% (29) 78.13% (150) 6.77% (13)
Commercial Dish
Waster 13.76% (26) 82.54% (156) 3.70% (7)
Waterbroom 10.99% (20) 85.16% (155) 3.85% (7)
Kitchen Spray
Rinse Valve
(complimentary)
22.10% (40) 77.90% (141) N/A
1“Yes, If Increased” was used for the respondent to advise of the dollar amount needed for them to be interested in a
rebate for the item.
Quantities and costs identified for Plan C were also determined with the goal of ensuring that the
program does not favor one customer class over another, in contrast to the way in which water
conservation programs that focus on turf replacement favor single-family homeowners. Therefore,
the $60,000 budget for water conservation rebates was divided evenly between seven water
conservation measures not currently offered by the Utilities Department for SFR, MFR, and CII
categories. $10,000 was also set aside for developing water budgets for large landscapes on CII
properties. The quantities included for each water conservation measure of Plan C represents a
conservation program plan that could be implemented with current staffing levels, funding,
resources, and expected community participation based on the results of the survey (Table 6).
Table 7 outlines the quantity and budgeted dollar amount for each water conservation measure
included for Plan C during Year 1 and Year 2.
Table 7. Quantity and Budget Allocated for Water Conservation Plan C.
Conservation Measure1 Year 1 Year 2
SFR High-Efficiency Toilet (1.28 GPF) 100 ($10,000) 100 ($10,000)
MFR High Efficiency Toilet (1.28 GPF) 44 ($4,400) 44 ($4,400)
MFR Large Landscape Smart Irrigation Controller 8 ($5,600) 8 ($5,600)
CII High-Efficiency Toilet (1.28 GPF) 70 ($7,000) 70 ($7,000)
CII High-Efficiency Urinal (0.125 GPF) 20 ($2,000) 19 ($1,900)
CII Restaurant Dipper Wells 7 ($1,050) 7 ($1,050)
CII Large Landscape Water Budgets 20 ($5,000) 20 ($5,000)
1Water conservation measures that were modeled but are already a part of the Utilities Department's standard water
conservation operations (water reports, audits, and complimentary items) are not included.
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City of San Luis Obispo Water Conservation and Efficiency Plan P a g e | 36
Results of Benefit-Cost Analysis
The AWE Tracker Tool provides a benefit-cost ratio for each water conservation measure in units
of dollar per AF of water saved. Water conservation measures with low benefit-cost ratios provide
lower water savings per dollar than the water conservation measures with high benefit-cost ratios.
As stated earlier, the development of Plan A included a large suite of water conservation
measures and serves to compare the benefit-cost ratios of those measures. The list of benefit-
cost ratios for all water conservation measures included in Plan A is provided in the Appendix.
Conservation programs Plan B and C included measures that had a benefit-cost ratio greater than
the median determined in Program A (29.7) as well as CII large landscape water budgets.
Although CII large landscape water budgets were determined to have a benefit-cost ratio lower
than the median (16.9), the water conservation measure was included in Plans B and C due to
the Utilities Department’s interested in determining water budgets for meeting forthcoming State
regulations regarding large CII landscapes.
Measures that are utilized daily, such as toilets, urinals, and showerheads, provide the highest
benefit-cost ratio. While water conservation measures that would be utilized infrequently, such as
rain barrels and graywater laundry to landscape systems, are some of the lowest benefit-cost
ratios. Turf replacement is also among the lowest benefit-cost ratio due to the high expense of
replacing each square foot. For this simulation, $1.00 per square foot with a maximum of 5,000
square feet available for replacement was utilized. Lastly, when comparing the expected savings
in gallons per day per unit to the benefit-cost ratio, MFR large landscape smart irrigation controller
and CII large landscape water budgets stand out as having the potential to produce a large water
savings but have a low benefit-cost ratio due to the high expense. Rebates for restaurant dipper
wells and commercial kitchen dishwashers also show a high expected savings compared to other
water conservation measures.
Water Savings and Cost Evaluation
The AWE Conservation Tracker Tool allows users to identify program cost parameters for each
water conservation measure, including the cost to the utility, any costs covered by a program
partner, and the cost to the program participant. For this analysis only the cost to the utility was
utilized as official offers from program partners have not been established and the cost to the
program participant is assumed to vary based on the specific device the participant choses to
purchase. The cost to the utility for each water conservation measure was determined based on
the recommended cost provided by AWE and the estimated maximum amount that the City would
provide, which was roughly half of the average cost for each measure.
Figure 7 shows the estimated water savings, total program costs, and per acre-foot cost of the
three water conservation programs that were evaluated. If all water conservation measures in
Plan A were implemented and utilized, a demand reduction of 1,814 AF is estimated over the
eighteen-year model period; however, it would cost the Utilities Department $341,646 with the
bulk of the total program costs occurs in the first two years due to implementation of rebate
programs. This equates to a cost of about $188 per AF of demand reduction. Demand reduction
is predicted to initially increase following the implementation of the rebate water conservation
measures and then remains relatively consistent for several years until decreasing as the
plumbing fixtures age and become less efficient, and the effects of the rebates diminish.
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City of San Luis Obispo Water Conservation and Efficiency Plan P a g e | 37
Figure 7. Estimated Water Savings and Program Costs for Water Conservation Plans A-C.
If only the water conservation measures with a high benefit-cost ratio identified in Plan B were
implemented and utilized, it is estimated that the City would experience 72% of the demand
reduction estimated in Program A (1,314 AF), while decreasing program costs by 56% during the
first two years (a $180,200 savings). The cost per acre-foot of demand reduction for Plan B is
about $123.
Lastly, with a constrained budget of $60,000 for rebate programs and $10,000 for developing
large landscape water budgets on CII properties, as identified in Plan C, it is estimated that the
City would experience 47% of the demand reduction estimated in Plan A (844 AF), while
decreasing program costs during the first two years by 78% (a $253,700 savings)Error!
Reference source not found.. The cost per acre-foot of demand reduction for Plan C is the
lowest of the three plans used in this evaluation, with a value of about $83.
1535
1071 739
279
243
105
$341,616
($188/AF)
$161,446
($123/AF)
$70,000
($83/AF)
$-
$50,000
$100,000
$150,000
$200,000
$250,000
$300,000
$350,000
$400,000
0
200
400
600
800
1,000
1,200
1,400
1,600
1,800
2,000
Plan A Plan B Plan C
Wa
t
e
r
S
a
v
i
n
g
s
(
A
F
)
Active Water Savings Passive Water Savings Total Program Cost
Page 151 of 555
7. FINAL WATER
CONSERVATION
PROGRAM
Selection Criteria
The development of this Water Conservation Plan utilized the AWWA Manual of Water Supply
Practices, M52 – Water Conservation Programs – A Planning Manual. Internally, the City
identified four goals of the water conservation rebate program, which carry over to the entire water
conservation program. These goals are:
• Support a community that already conserves water.
• Increase conservation among CII properties.
• Maximize water savings with available resources.
• Create a plan that is equitable across all user groups.
When a community has largely embraced water conservation as a way of life, such as San Luis
Obispo, it is important to support the programming that has provided that success and to avoid
demand hardening. As such, several of the water conservation measures included in the City’s
final water conservation plan are continuations of previous measures, such as communication,
outreach, education, and home water reports. Given that 69% of the City’s water use is attributed
to residential water use, historical water conservation programs have focused heavily on providing
water devices and rebates to residential customers.
Description of Program Components
Continued Programming
The City will continue the operational, external, and regulatory programs outlined in Section 4 of
this plan. By leveraging the knowledge gained from the implementation of these programs over
the years, these programs can become more refined, targeted, and impactful.
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City of San Luis Obispo Water Conservation and Efficiency Plan P a g e | 39
New Measures Selected
The City has implemented (as of January 1, 2023) the water conservation measures from Plan
C, described in Section 6 of this report. This includes rebates for the following:
• Single-Family Residential High-Efficiency Toilets
• Multi-Family Residential High-Efficiency Toilets
• Multi-Family Residential Large Landscape Smart Irrigation Controllers
• Commercial, Industrial, and Institutional High-Efficiency Toilets
• Commercial, Industrial, and Institutional High-Efficiency Urinals
• Restaurant Dipper Wells
Staff are in the process of updating and developing water budgets for City parks and recycled
water sites. A third party will be hired to develop additional water budgets for select CII properties
that have a DIM. These budgets will allow city staff to identify customers that are over budget and
offer assistance to help lower their water use by improving irrigation system performance and
management. Understanding if a property is exceeding a water budget will help ensure efficient
water use and that the City remain in compliance with the supplier level requirements for the
State’s CII Standard and Performance Measure requirements.
Future Options
Following regularly scheduled evaluations of the water conservation program, the City may
implement water conservation measures included in Plan B in addition to, or in place of, the water
conservation measures included in Plan C. Existing water conservation measures will be
evaluated for community participation and water savings to determine if changes to the program
are necessary. Changes will be made based on the information gathered during the conservation
plan development detailed in Section 6 of this report and available City resources. The City is also
developing programs and processes that should result in water conservation, in addition to water
conservation measures, some of which are described below.
The City of San Luis Obispo is in the process of converting its water meters from mechanical
meters to ultrasonic digital meters that will be compatible with AMI. AMI enables two-way
communication between water providers and consumers for monitoring and managing water
usage. The benefits of AMI include real-time monitoring, leak detection, demand management,
and customer engagement which can improve operational efficiency, conserve water, and
enhance customer service. The movement towards AMI citywide will require a significant work
effort from the City, including replacing all existing mechanical meters, installation of cellular
hardware, establishing a reliable communication network and robust data management system,
and educating customers regarding the transition. AMI-compatible water meters provide many
benefits, even if the system is not converted to an AMI system.
City staff are also currently participating in the AWE learning cohort on cooling towers. The goal
of this program is to bring together water utilities across the nation to discuss rebates or regulatory
requirements that encourage efficient water use for cooling towers. The City is in the process of
evaluating if an incentive or regulatory based cooling tower water conservation measure could be
implemented depending on projected water savings, funding, and staff availability.
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City of San Luis Obispo Water Conservation and Efficiency Plan P a g e | 40
The City is developing a strategy to update its method for estimating water supply and demand
using land use-based demand projections instead of the current method which uses population
and the SB X7-7 water use target. This method will mirror the methods used by the California
Department of Water Resources in determining UWUOs.
Projected Water Savings
Table 8 shows the projected per capita water use in AF in 5-year increments for the projected
demand with no plumbing code savings, projected demand with plumbing code savings, and
projected demand with plumbing code savings and the recommended program implementation.
It should be noted that not all of the water conservation measures, such as public outreach,
educational programs, and water waste regulations, could be quantified to be included in the
model. Furthermore, these estimates assume that the quantity of the measure is fully utilized (i.e.
the anticipated number of rebates are fully utilized by the community).
Table 8. Projected Water Demands.
2025 2030 2035 2040
Population 51,317 53,934 57,200 60,118
“Baseline” Demand without Plumbing Code (acre-
feet)
5,213 5,638 6,092 6,578
Demand with Plumbing and Landscape Standards
(acre-feet)
4,922 5,128 5,372 5,665
Demand with Plumbing and Landscape Standards
and Recommended Program Plan C (acre-feet)
4,883 5,093 5,360 5,660
Additional Benefits
Water conservation programs provide benefits ancillary to water savings and prolonging water
supplies. Water conservation programs are instrumental in helping water utilities meet water use
objective and leak reduction compliance goals, which are paramount in California. Reducing per
capita water use alleviates the need for expanded water supplies or water treatment and
distribution infrastructure, which results in deferred infrastructure upgrades. Also, reducing water
use is directly related to decreased energy consumption, which reduces greenhouse gas
emissions and can also reduce energy costs for the utility and the water customers.
Regulatory Compliance
Although the City is currently below the SB X7-7 required 117 GPCD, implementation of the Water
Conservation and Efficiency Plan will ensure that total GPCD remains low as population continues
to increase. Additionally, various measurable objectives outlined in Conclusion of this plan are
requirements of SB 606 and AB 1668 regardless of whether annual water use is below the
calculated Urban Water Use Objectives (UWUO)38. Periodic reviews and updates will ensure that
38 The California Urban Water Use Objectives are calculated following California Water Code §10609.20, which can
be accessed at:
https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?sectionNum=10609.24.&lawCode=WAT
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City of San Luis Obispo Water Conservation and Efficiency Plan P a g e | 41
the Water Conservation and Efficiency Plan remains current with the most up-to-date regulatory
requirements and industry best practices, which will help the City to maintain its compliance with
relevant water conservation regulations. Ultimately, the implementation of the Water
Conservation and Efficiency plan is a proactive approach to ensure that the City meets its
regulatory obligations, even as population increases and weather becomes more unpredictable.
Leak Reduction
In addition to a reduction in overall water usage, implementation of the Water Use and Efficiency
Plan will also lead to water savings through a reduction in water leaks. Water leaks result in
wasteful energy and financial resources. Not only does water that is lost because of a leak require
additional energy to pump and treat the lost water, but water leaks can also cause costly damage
to infrastructure. On an individual level, customers face high bills and potential structural damage
and mold growth. For the City, small leaks will eventually turn into larger leaks, such as main line
breaks in the distribution system, that require extensive financial resources such as staff time and
materials. Larger breaks may also disrupt water pressure, thus affecting the efficiency and
effectiveness of the overall supply. Measures that specifically focus on leak detection and repair,
such as AMI, will help to ensure that any leaks in the system are promptly identified and fixed.
Moreover, by raising awareness about the importance of water conservation among the
community, the plan encourages individuals to adopt water-saving behaviors, such as addressing
leaks as soon as they are identified. Through these efforts, the City can significantly reduce overall
water system leakage both internally and externally throughout the community.
Deferred Infrastructure Upgrades
Implementation of the Water Conservation and Efficiency Plan can also significantly contribute to
deferring infrastructure upgrades related to water supply acquisition, treatment, and distribution.
By reducing water demand through water conservation measures, the need to construct additional
water supply sources or expand existing treatment facilities is reduced. This can result in
considerable cost savings and a reduction in carbon emissions, energy use, and environmental
impacts associated with the construction of new facilities. Therefore, the implementation of the
Water Conservation and Efficiency Plan can be an effective strategy for the City to manage its
water resources sustainably while minimizing the need for costly and potentially disruptive
infrastructure upgrades.
Greenhouse Gas Reductions
Water conservation and efficiency also often have ancillary benefits of reductions in energy use
and greenhouse gas (GHG) emissions associated with water supply, treatment, and use. GHG
emissions are released during water supply pumping, treatment, and distribution, the treatment
of wastewater, and if there is any energy associated with the operation of appliances and
equipment that require water for end-users. By reducing water demand through water
conservation, the City can reduce the energy required for water pumping and treatment and the
community can reduce the energy required for use, thus resulting in a decrease in GHG
emissions. Additionally, by deferring infrastructure updates, GHG emissions related with
construction and maintenance activities such as the use of heavy equipment can be avoided.
The City of San Luis Obispo established a community-wide goal to reduce community greenhouse
gas emissions to reach carbon neutrality by 2035. The City has established a culture of using
resources mor effectively and strive to improve community equity and well-being.
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For the estimated amount of water saved through the implementation of this plan, there is an
estimated embedded energy intensity savings of 2,177 kilowatt-hours per acre-foot (kWh/AF). By
multiplying the water savings times the energy intensity and a GHG emission factor estimated by
PG&E this converts to an estimated 2,106 pounds of carbon dioxide (CO2) equivalent per AF. It
should be noted that emission factors are estimated based on the California Public Utilities
Commission calculator and that additional GHG savings from hot water savings at the end user
level and from reduced wastewater collection, treatment, and disposal energy are not quantified.
Total projected annual CO2 equivalent savings for each year are estimate in Table 9.
Table 9. Estimated CO2 Savings from Implementation of the Selected Water Conservation Program.
Year Cumulative Tons of CO2 Equivalent Savings
2025 2,581
2030 8,582
2035 17,004
2040 27,515
Next Steps
Annual monitoring and reporting of the City’s water supply status will continue, and updates to
the City’s UWMP and WSCP will continue on a five-year cycle. The City understands that water
use is dynamic and responds to changes in population, economy, weather, regulations, and
technology. Therefore, the City may adjust water conservation targets and schedules as needed.
This may include expanding or scaling back various water conservation measures to meet budget
and staffing restrictions, increase efficiency, or adopt new technologies or better methods. With
the calculated water savings identified for various water conservation measures in this plan, the
City will be able to adjust program components to strive to meet the measurable objectives
discussed below.
Implementation Schedule
The Water Conservation and Efficiency Plan will act as a road map, outlining anticipated new
water conservation measures until 2040. Table A6 in the Appendix of this report shows the
implementation schedule for the planned conservation measures. However, the implementation
schedule will remain adaptable over time, as it is subject to modifications based on changes in
budget and staffing resources. The determination of specific measures will be guided by key
questions, including but not limited to:
• What level of support will be required from conservation staff to implement and maintain
the selected water conservation measures?
• What other support is needed (e.g. outsourced support or other sources of funding) or
wanted to implement and maintain these programs?
• Does the conservation measure meet other Departmental objectives?
• How quickly can the conservation measure be implemented?
It should be noted that although new water conservation measures may be implemented on
schedule, high participation rates will be crucial to achieving the estimated demand reduction and
measurable objectives outlined below. Therefore, the following benchmarks will be used to help
gauge progress and determine the effectiveness of the individual measures that are implemented.
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City of San Luis Obispo Water Conservation and Efficiency Plan P a g e | 43
Measurable Objectives
Baseline Water Usage and Water Use Efficiency Standards
Baseline water use will serve as a reference point for measuring future reductions and efficiency
improvements. Water use efficiency standards set by the State, or locally, will define the upper
limit of water use targeted by the City’s water conservation program. A water conservation
program that results in water use below these standards will be considered a success.
Participation Rates
Staff will track the number of items offered and level of participation from individuals, households,
community groups, and businesses for water conservation measures that are implemented. This
will include the number of:
• Rebates approved
• Tours provided
• Youth education classes offered
• Plans reviewed for conformance with MWELO requirements
• Complimentary water conservation items provided
• Technical assistance visits conducted
• Water waste violations investigated
• Plumbing retrofit certifications approved
Cost Per AF Saved
Staff will monitor water use for program participants that can be tracked, such as rebate programs,
to determine the cost to the Utilities Department per acre-foot of water saved.
These benchmarking metrics will then be used during the performance tracking and review
process to modify the overall program and improve future processes and procedures.
Budget and Staffing
In recent years, water agencies have recognized the value of water conservation as an essential
component of their water supply portfolio. Conserving water not only reduces the need for
additional water extraction, treatment, and distribution, but also mit igates the necessity for
securing extra water sources to meet future demands and buffer supplies. The estimated cost of
water saved per unit volume ($/AF) for the Final Water Conservation measures outlined in this
plan is $83/AF. This cost is lower than the average expense of obtaining, treating, and distributing
water from the City’s three surface water reservoirs, which is currently estimated to be about
$276/AF.39 Consequently, water conservation serves as a cost-effective solution when
considering the expenses of future water supplies.
The budget for the City’s Water Conservation Program may vary, particularly during drought
periods. For instance, additional funds were allocated in the City’s 2022-23 Budget Supplement
to support increased public outreach, hire additional support staff, and launch a new water
conservation rebate program, all in response to the drought. Therefore, staff will use the Water
Conservation and Efficiency Plan as a roadmap to implement water conservation measures that
39 This is the variable production cost estimated in the City’s 2021 Water Loss Audit. This is the cost to produce and
supply the next unit of water and can include both short -run and long-run marginal costs.
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City of San Luis Obispo Water Conservation and Efficiency Plan P a g e | 44
have the potential to create the largest water savings while aligning with the City’s current financial
or mid-year financial plan. Staff will also aim to actively seek partnerships and apply for grants
that maximize support for water conservation measures as staffing and resources allow.
Performance Tracking and Review
The use of measurable objectives will help clearly identify the overall progress and performance
of the City’s Water Conservation and Efficiency Plan. Staff will track the participation and
effectiveness of individual water conservation measures through the benchmarks identified above
and the overall performance of the plan through the following measurable objectives listed below.
Measurable objectives were chosen based on historical tracking and current and anticipated
future regulatory compliance metrics.
• Meet the City’s UWMP GPCD target and current state GPCD regulations annually.
• Meet the state’s requirements for outdoor residential landscape standards annually.
• Meet the state’s water loss standards in gallons per connection per day annually.
• Document increased water use efficiency for CII DIMs.
• Document increased water use efficiency for the highest 20% water-users for each
classification of CII properties (excluding process water use).
• Document increased water use efficiency for the top 5% of individual CII accounts
(excluding process water use).
After compiling the measurable objectives, staff will conduct a comprehensive review and analysis
to determine the extent to which these objectives were met or fell short. This evaluation will enable
the staff to identify programs or customer groups that m ay require additional resources, staff
allocation, or funding to ensure the ongoing fulfillment of the community's Water Conservation
and Efficiency Plans goals. Furthermore, these reviews will serve as an opportunity to incorporate
new ideas and regulatory requirements, thereby ensuring that the City not only complies with but
also surpasses water conservation regulations. The findings of these reviews and potential
updates will be provided in the City’s annual Water Supply and Demand Assessment and five-
year UWMP in accordance with the policies and procedures identified in the City’s General Plan
WWME. The Water Conservation and Efficiency Plan will be reviewed and updated at least once
every five years.
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8. CONCLUSION
The City’s Water Conservation and Efficiency Plan uses the latest tools and information to
develop a conservation plan that builds on the City’s history of building a strong water
conservation ethic. This plan aims to proactively meet State mandated water use efficiency
standards using an equitable, budget-conscious approach. Development of the latest water
conservation program has provided information that will be used to modify future water
conservation programs as needed, to maximize community participation and water savings.
The following is a summary of the key findings of this plan. These key findings demonstrate the
City’s commitment to strategic and sustainable water management practices that will help ensure
the City of San Luis Obispo continues to have a resilient water future.
Water Savings and Ancillary Benefits
The water conservation program developed as part of this Water Conservation and Efficiency
Plan is estimated to save as much as 844 AF/Year. This water remains in the City’s available
water supplies to provide for future demand, or as Reliability Reserve or Secondary Water Supply.
Additional benefits to implementing this water conservation program include regulatory
compliance, leak reduction, deferred infrastructure upgrades, and reducing greenhouse gasses
and energy costs.
Enhanced Understanding
The utilization of emerging tools for the development of this plan has provided the City with a
deeper understanding of water demand and the potential impact of water conservation measures
on future water conservation efforts. Implementation of the Water Conservation and Efficiency
Plan will allow the City to continue to integrate innovative techniques and tools into the
community’s water conservation practices moving forward.
Integral Role of Conservation
Water conservation has played a crucial role in the City’s water supply planning and has allowed
the City to ensure the fulfillment of foreseen and unforeseen water demands and regulatory
obligations. Water conservation preserves available water supplies for unforeseen short-term
demands and preserves stored water resources to be used during future droughts. The
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City of San Luis Obispo Water Conservation and Efficiency Plan P a g e | 46
measurable objectives in this plan will align the City with that State’s “Making Water Conservation
a California Way of Life” legislation (SB 606 and AB 1668). Therefore, the City will be able to
utilize the Water Conservation and Efficiency Plan to fulfill its compliance obligations to meet
regulatory requirements as these and other new water conservation regulations are put in place
by the state and federal governments.
Cost-Effectiveness
Conservation is recognized as one of the most cost-effective strategies for meeting current and
future water needs. The implementation of the water conservation measures identified in this plan
has the potential to reduce the necessity for further infrastructure upgrades and expansion.
Additionally, the ability of the Conservation Tracker Tool to provide estimates of benefit-cost ratios
of conservation measures allows the City to implement a cost-effective water conservation
program.
Proactive Management
The Water Conservation and Efficiency Plan aligns with the City’s approach to actively managing
water supply to meet both current and future demands under various climate scenarios, helping
to ensure long-term water sustainability. The plan provides metrics that can be used to estimate
future water savings and to measure the effectiveness of the water conservation program. Should
the program not meet the City’s goals, the plan provides alternative pathways that can be utilized
to help improve program effectiveness. Coupled with the tools the City has historically used to
proactively manage its water resources, the Water Conservation and Efficiency Plan adds another
layer to the City’s informed decision making.
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9. APPENDIX
Table A 1. Commercial, Industrial, and Institutional (CII) Water Account Classifications
Class Code Class Code Definition
Airport This includes all meters that service the San Luis Obispo County
Regional Airport.
Auto Services This includes all meters that service commercial automobile services,
including mechanics, detailing services, gas stations, motor vehicle
sales, towing services, and vehicle rentals. Please note that this does
not include meters that service car wash facilities.
Car Wash This includes all meters that service the various types of car washes:
self-service, automated, hand wash, etc. Gas stations that include car
washes should be categorized as "Auto Services".
Cemetery This includes all meters that service areas with graves, tombs, and
funeral urns.
City Facility This includes all meters that service City of SLO buildings and facilities
that are not associated with City of SLO parks (i.e. City Hall, 879
Morro, etc.)
City Park Facility This includes all meters that service City of SLO park facilities (i.e. park
restrooms, park water fountains, etc.).
Convenience
Store
This includes all meters that service convenience stores, including
liquor stores.
Entertainment with
Food
This includes all meters that service entertainment facilities that provide
customers food services (i.e. theaters and bowling allies).
Entertainment
without Food
This includes all meters that service entertainment facilities that do not
offer customers food services (i.e. museums).
Food and
Beverage
This includes all meters that service full-service restaurants, bars, fast
food eateries, catering services, service bakeries, cafes, and coffee
shops.
Grocery Store This includes all meters that service grocery stores and supermarkets.
Group Live-in This includes all meters that service facilities providing rehabilitation
services, such as housing and drug and alcohol rehabilitation.
Health Care This includes all meters that service public and private hospital
facilities, private medical centers, doctors’ offices, labs, and long-term
nursing homes: institutions equipped to care for people unable to look
after themselves, as the aged or chronically ill. Please note that there is
a separate category for retirement homes.
Hotel/Motel This includes all meters that service properties identified by the
downtown association to be a hotel or motel.
Industrial This includes all meters that service industrial facilities, including
manufacturing and warehousing facilities.
Laundry Facility This includes all meters that service commercial laundry services and
dry-cleaning facilities. Please note that there is a separate category for
residential laundry facilities.
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City of San Luis Obispo Water Conservation and Efficiency Plan P a g e | 48
Misc Commercial This includes all meters that service commercial facilities that do not
fall into any of the commercial categories identified above.
Office This includes all meters that service office buildings.
Other Public
Facility
This includes all meters that service public institutional facilities not
owned by the City of SLO (i.e. County/State/Federal administrative
offices, post offices, public use buildings, etc.)
Pool This includes all meters that service community pools.
Preschool/Daycare This includes all meters that service commercial and non-profit
childcare services. Religious institutions that include child services
should still be listed as religious buildings if there is only one meter.
School This includes all meters that service public and private primary and
secondary educational institutions. Please note that there is a separate
category for Cal Poly meters under the Other category.
Religious Building This includes all meters that service religious facilities.
Residential
Laundry
This includes all meters that service only laundry facilities on residential
properties (i.e. non-commercial).
Retirement Home This includes all meters that service retirement facilities: institutions
equipped to care for people who are independent but want to be able
to access care and support if they need it. Please note nursing homes
fall under the Health Care class code.
Sales/Services This includes all meters that service retail and service stores,
commercial shopping centers, commercial personal service facilities
(such as beauty salons, massage facilities, and fitness/recreational
facilities), or business centers that include a variety of commercial
businesses.
Utility This includes all meters that service non-City run utility facilities (i.e.
gas, electric, etc.)
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City of San Luis Obispo Water Conservation and Efficiency Plan P a g e | 49
Table A 2. Plan A Water Conservation Measure Parameters.
Water Conservation Measure
Cost to
Utility
($/Unit)
Quantity
Year 1
Quantity
Year 2
Quantity
(Annual
Thereafter)
SFR Home Water Report $0.00* 250 250 250
SFR ULFT Replacement (1.6 GPF) $100.00 100 100 -
SFR HET Replacement (1.28 GPF) $100.00 100 100 -
SFR Washer Rebate (WF <=4) $150.00 40 40 -
SFR Showerhead Replacement (<= 1.8 GPM) $6.00** 50 50 50
SFR Smart Irrigation Controller Rebate $130.00 20 20 -
SFR Turf Replacement $1.00/sq ft 5000 5000 -
SFR Graywater Laundry to Landscape
Rebate $200.00 10 10 -
SFR Rain Barrel (< 200 gal) Rebate $50.00 20 20 -
MFR Water Use Audit $0.00* 250 250 250
MFR ULFT Replacement (1.6 GPF) $100.00 100 100 -
MFR HET Replacement (1.28 GPF) $100.00 100 100 -
MFR In-Unit Washer Rebate (WF <=4) $150.00 100 100 -
MFR Shared Washer Rebate (WF <=4) $350.00 20 20 -
MFR Showerhead Replacement (<= 1.8
GPM) $6.00** 10 10 10
MFR Large Landscape Smart Irrigation
Controller Rebate $700.00 12 12 -
MFR Turf Replacement $1.00/sq ft 5000 5000 -
CII ULFT Replacement (1.6 GPF) $100.00 100 100 -
CII HET Replacement (1.28 GPF) $100.00 100 100 -
CII Urinal (Waterless) Replacement $100.00 12 12 -
CII Urinal (1/8 GPF) Replacement $100.00 12 12 -
CII Washer Rebate (WF <=4) $350.00 14 14 -
CII Commercial Kitchen Dishwasher Rebate $700.00 7 7 -
CII Commercial Kitchen Spray Rinse Valve
Rebate $31.85** 20 20 20
CII Commercial Kitchen Food Streamer
Rebate $1,400.00 7 7 -
CII Restaurant Dipper Well Rebate $150.00 7 7 -
CII Large Landscape Irrigation Controller $1400.00 12 12 -
CII Large Landscape Turf Replacement $1.00/sq ft 5000 5000 -
CII Large Landscape Water Budget $250.00 20 20 -
*SFR Home Water Report and MFR Water Use Audits set to $0.00 because this is a standard service that Water
Resources staff provides the community.
**SFR/MFR showerheads and CII Kitchen Spray Rinse Valves are kept at their true cost in Program 1 to compare to
other measures.
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City of San Luis Obispo Water Conservation and Efficiency Plan P a g e | 50
Table A 3. Benefit-Cost Ratio for Conservation Measures Included in Plan A.
Water Conservation Measure Benefit-
Cost Ratio
SFR Rain Barrel (< 200 gal) Rebate 0.6
SFR Graywater Laundry to Landscape Rebate 2.1
MFR Turf Replacement 3.7
CII Large Landscape Turf Replacement 3.7
SFR Turf Replacement 3.7
SFR Smart Irrigation Controller Rebate 7.6
MFR In-Unit Washer Rebate (WF <=4) 8.3
CII Commercial Kitchen Food Steamer Rebate 10.0
SFR Washer Rebate (WF <=4) 12.4
MFR Shared Washer Rebate (WF <=4) 16.5
CII Washer Rebate (WF <=4) 16.5
CII Large Landscape Water Budget 16.9
CII Large Landscape Irrigation Controller 19.7
SFR ULFT Replacement (1.6 GPF) 29.5
CII Commercial Kitchen Dishwasher Rebate 29.7
CII Commercial Kitchen Spray Rinse Valve Rebate 39.6
CII ULFT Replacement (1.6 GPF) 41.1
MFR ULFT Replacement (1.6 GPF) 42.6
MFR Large Landscape Smart Irrigation Controller Rebate 62.8
SFR Home Water Report 100.0
MFR Water Use Audit 100.0
SFR HET Replacement (1.28 GPF) 105.3
CII Restaurant Dipper Well Rebate 109.2
CII Urinal (1/8 gpf) Replacement 116.6
MFR HET Replacement (1.28 GPF) 117.0
CII Urinal (Waterless) Replacement 126.2
CII HET Replacement (1.28 GPF) 146.5
MFR Showerhead Replacement (<= 1.8 GPM) 175.9
SFR Showerhead Replacement (<= 1.8 GPM) 175.9
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City of San Luis Obispo Water Conservation and Efficiency Plan P a g e | 51
Figure A 1. Plan A Annual Program Water Savings.
Table A 4. Plan B Water Conservation Measure Parameters.
Water Conservation Measure Utility
($/Unit)
Quantity
Year 1
Quantity
Year 2
Quantity
(Annual
Thereafter)
SFR Home Water Report $0.00* 250 250 250
SFR HET Replacement (1.28 GPF) $100.00 100 100 -
SFR Showerhead Replacement (<= 1.8 GPM) $6.00** 50 50 50
MFR Water Use Audit $0.00* 250 250 250
MFR HET Replacement (1.28 GPF) $100.00 100 100 -
MFR ULFT Replacement (1.6 GPF) $100.00 100 100 -
MFR Showerhead Replacement (<= 1.8 GPM) $6.00** 10 10 10
MFR Large Landscape Smart Irrigation
Controller Rebate
$700.00 12 12 -
CII HET Replacement (1.28 GPF) $100.00 100 100 -
CII ULFT Replacement (1.6 GPF) $100.00 100 100 -
CII Urinal (1/8 GPF) Replacement $100.00 12 12 -
CII Urinal (Waterless) Replacement $100.00 12 12 -
CII Commercial Kitchen Dishwasher Rebate $700.00 7 7 -
CII Commercial Kitchen Spray Rinse Valve
Rebate
$31.85** 20 20 20
CII Restaurant Dipper Well Rebate $150.00 7 7 -
CII Large Landscape Water Budget $250.00 20 20 -
*SFR Home Water Report and MFR Water Use Audits set to $0.00 because this is a standard service that Water
Resources staff provides the community.
**SFR/MFR showerheads and CII Kitchen Spray Rinse Valves are kept at their true cost in Program 2 to compare to
other measures. However, these measures would fall under the standard $5,000 annual complimentary water
conservation item budget.
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City of San Luis Obispo Water Conservation and Efficiency Plan P a g e | 52
Figure A 2. Plan B Annual Program Water Savings.
Figure A 3. Benefit Cost Ratio Versus Expected Water Savings
CII Large Landscape
Water Budgets
CII Commercial Kitchen
Dishwasher Rebate
MFR Large Landscape Smart
Irrigation Controller Rebate
CII Restaurant Dipper
Well Rebate
0
200
400
600
800
1000
1200
1400
0 5 10 15 20
Ex
p
e
c
t
e
d
W
a
t
e
r
S
a
v
i
n
g
s
(
G
P
D
/
U
n
i
t
)
Benefit-Cost Ratio
CII Large Landscape Water Budgets CII ULFT Replacement (1.6 GPF)
MFR ULFT Replacement (1.6 GPF)CII Commercial Kitchen Dishwasher Rebate
CII Commercial Kitchen Spray Rinse Valve Rebate MFR Large Landscape Smart Irrigation Controller Rebate
SFR Home Water Report MFR Water Use Audit
SFR HET Replacement (1.28 GPF)CII Restaurant Dipper Well Rebate
CII Urinal (1/8 gpf) Replacement MFR HET Replacement (1.28 GPF)
CII Urinal (Waterless) Replacement CII HET Replacement (1.28 GPF)
MFR Showerhead Replacement (<= 1.8 gpm)SFR Showerhead Replacement (<= 1.8 gpm)
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City of San Luis Obispo Water Conservation and Efficiency Plan P a g e | 53
Table A 5. Plan C Water Conservation Measure Parameters.
Water Conservation Measure Utility
($/Unit)
Quantity
Year 1
Quantity
Year 2
Quantity
(Annual
Thereafter)
SFR Home Water Report $0.00* 250 250 250
SFR HET Replacement (1.28 GPF) $100.00 100 100 -
SFR Showerhead Replacement (<= 1.8 GPM) $0.00** 50 50 50
MFR Water Use Audit $0.00* 250 250 250
MFR HET Replacement (1.28 GPF) $100.00 44 44 -
MFR Showerhead Replacement (<= 1.8 GPM) $0.00** 10 10 10
MFR Large Landscape Smart Irrigation
Controller Rebate
$700.00 8 8 -
CII HET Replacement (1.28 GPF) $100.00 70 70 -
CII Urinal (1/8 GPF) Replacement $100.00 20 19 -
CII Commercial Kitchen Spray Rinse Valve
Rebate
$0.00** 20 20 20
CII Restaurant Dipper Well Rebate $150.00 7 7 -
CII Large Landscape Water Budget $250.00 20 20 -
*SFR Home Water Report and MFR Water Use Audits set to $0.00 because this is a standard service that Water
Resources staff provides the community.
**Price set at $0.00 because the measure is included in the standard $5,000 annual complimentary water conservation
item budget.
Figure A 4. Plan C Annual Program Water Savings.
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City of San Luis Obispo Water Conservation and Efficiency Plan P a g e | 54
Table A 6. Implementation Schedule.
Mea
sure Ye
a
r
1
Ye
a
r
2
Ye
a
r
3
Ye
a
r
4
Ye
a
r
5
Ye
a
r
6
Ye
a
r
7
Ye
a
r
8
Ye
a
r
9
Ye
a
r
1
0
Ye
a
r
1
1
Ye
a
r
1
2
Ye
a
r
1
3
Ye
a
r
1
4
Ye
a
r
1
5
Ye
a
r
1
6
Ye
a
r
1
7
Ye
a
r
1
8
Pu
blic
Inf
or
mat
ion
and
Out
rea
ch
Ho
me
Wa
ter
Us
e
Re
por
ts
Lea
k
As
sist
anc
e
Plu
mbi
ng
Ret
rofi
t
Pro
gra
m
Co
mpl
ime
nta
ry
Co
nse
rva
tio
n
Ite
ms
Wa
ter
Effi
cie
nt
Lan
dsc
ape
Ord
ina
nce
Hig
h
Effi
cie
ncy
Toil
et
Re
bat
e
(1.2
8
GP
F)
Uri
nal
Re
pla
ce
me
nt
Re
bat
e
(1/8
GP
F)
Larg
e
Lan
dsc
ape
Sma
rt
Irrig
atio
n
Con
troll
er
Reb
ate
CII
Re
sta
ura
nt
Dip
per
Wel
l
Re
bat
e
CII
Lar
ge
Lan
dsc
ape
Wa
ter
Bu
dge
ts
Ex
pan
ded
Wa
ter
Us
e
Au
dits
Ad
van
ced
Met
eri
ng
Infr
ast
ruc
tur
e
(A
MI)
On
goi
ng
Sys
tem
Wat
er
Los
s
Red
ucti
on
Pro
ject
s
Co
mm
erci
al
Kit
che
n
Dis
hw
ash
er
Re
bat
e
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