HomeMy WebLinkAbout12-12-2017 Item 10 - 2017 Water Resources Status ReportMeeting Date: 12/12/2017
FROM: Carrie Mattingly, Utilities Director
Prepared By: Aaron Floyd, Utilities Deputy Director - Water
Jennifer Metz, Utilities Projects Manager
Mychal Boerman, Water Resources Program Manager
SUBJECT: 2017 WATER RESOURCES STATUS REPORT
RECOMMENDATION
Receive and file the 2017 Water Resources Status Report.
DISCUSSION
The 2017 Water Resources Status Report (2017 Report; Attachment A) provides an overview
and update on the City's water resources. This report covers Water Year 2017; which extends
from October 1 through September 30. These reports have been provided to the City Council and
community since 1985 and serve to both inform future policy decisions as well as provide
historical documentation of water conditions.
2016 Water Year
Summary
2017 Water Year
Summary Change
Total Water Use: 4,731 acre feet 4,975 acre feet +344 acre feet
Potable Water Use 4,529 acre feet 4,746 acre feet +217 acre feet
Recycled Water Use 202 acre feet 229 acre feet +27 acre feet
2017 Population 46,117 residents 46,724 residents +607 residents
Per Capita Demand Per Day (Potable Only) 88 gallons 91 gallons +3 gallons
Water Projection Model
(as of September 30, 2017) >5 years of supply >5 years of supply -
Water Resource Availability: 12,109 acre feet 12,115 acre feet +6 acre feet
Salinas & Whale Rock Reservoirs 6,940 acre feet 6,940 acre feet -
Nacimiento Reservoir 5,482 acre feet 5,482 acre feet -
Recycled Water (from 2016) 187 acre feet 193 acre feet +6 acre feet
Siltation (from 2010 to 2060)1 (500) acre feet (500) acre feet -
Water Supply Accounting: 12,109 acre feet 12,115 acre feet +6 acre feet
Primary Water Supply 2 7,496 acre feet 7,496 acre feet -
Reliability Reserve 3 1,209 acre feet 1,225 acre feet +16 acre feet
Secondary Water Supply 4 3,404 acre feet 3,394 acre feet -10 acre feet
NOTES:
1.Siltation losses at Salinas and Whale Rock Reservoirs are accounted for consistent with General Plan Policy A 4.2.2, The
City’s water supply from Nacimiento Reservoir is a contractual supply and would not be reduced by siltation losses.
2.Per General Plan Policy A 5.2.2, primary water supply is the amount of water needed for General Plan build -out using the
water use rate established by policy A 5.2.1 (117 gallons per capita per day).
3.Per General Plan Policy A 5.2.3, reliability reserve that is 20 -percent of the water use rate established in Policy A 5.2.1
multiplied by the City’s current population (46,724 in 2017).
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4. Per General Plan Policy A 5.2.4, secondary water supply is the remaining City water supply available after accounting for
primary water supply and a reliability reserve.
5. Values are rounded.
The 2017 Report was prepared in accordance with the General Plan, Water and Wastewater
Management Element, Policy A5.3.1. Highlights from the 2017 Report include:
• Beginning in October 2016, the City received abundant rainfall with over 35 inches at
San Luis Obispo Reservoir, where average annual rainfall is approximately 25 inches.
• In January, the City declared Climate Action a top priority during its major city goal-
setting workshop and identified objectives focused on energy efficiency and
greenhouse gas reductions within City facilities, such as the City’s Water Treatment
Plant and Water Resource Recovery Facility.
• In March, the City Council adopted a resolution approving the 2017 Recycled Water
Master Plan and authorized staff to negotiate an agreement for delivery of recycled
water outside the city limits consistent with policies and findings identified in the
General Plan.
• In April, Governor Brown issued Executive Order B-40-17 ending the drought state
of emergency in California and eliminating the City’s mandated 12 percent water use
reduction.
• In May, the City became a Groundwater Sustainability Agency over the area of the
San Luis Obispo Valley Groundwater Basin that lies beneath and within its
jurisdictional boundaries. In that role, the City will work collaboratively with other
stakeholders to comply with Sustainable Groundwater Management Act requirements
for the entire groundwater basin.
• In June, the City Council adopted resolutions to rescind the drought emergency
locally.
• In September, the City completed its first annual standardized water loss audit as
required by the Department of Water Resources.
ENVIRONMENTAL REVIEW
The 2017 Water Resources Status Report 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
contemplated by Title 14, California Code of Regulations, Section 15378.
CONCURRENCES
Community Development concurs with the environmental review findings.
FISCAL IMPACT
There are no fiscal impacts associated with the recommended action.
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Attachments:
a - 2017 Water Resources Status Report
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2017
Water Resources
Status Report
For the Time Period October 1, 2016 through September 30, 2017
Photo Credit: City of San Luis Obispo.
PREPARED BY:
Jennifer Metz, Utilities Projects Manager
Aaron Floyd, Utilities Deputy Director - Water
Mychal Boerman, Water Resources Program Manager
Salinas Reservoir (2015) Salinas Reservoir (2017)
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The City’s 2017 Water Resources Status Report includes water production and water consumption data
for October 1, 2016 through September 30, 2017 and was prepared in accordance with the General Plan,
Water and Wastewater Management Element, Policy A5.3.1. The reporting period corresponds to the
Water Year (October 1 through September 30), the 12-month period for which precipitation totals are
measured designated by the calendar year in which it ends. This report for Water Year 2017 is organized as
follows:
I. Drought Declaration Rescinded and Water Policy Update
II. Water Supply
III. Water Demand
IV. Water Resource Availability
V. Water Supply Accounting
VI. Water Demand Management
I. DROUGHT DECLARATION RESCINDED AND WATER POLICY UPDATE
Following abundant rainfall this past winter, on April 7, 2017 Governor Brown issued Executive Order B-
40-17 ending the drought state of emergency in California and eliminating the City’s mandated 12 percent
water use reduction. The City Council adopted resolutions to rescind the drought emergency locally on
June 20, 2017.
A 2016 Executive Order (B-37-16),
approved by Governor Brown on May 9,
2016, bolsters California’s drought
resilience and preparedness by establishing
longer-term water conservation measures
that include permanent monthly water use
reporting, new urban water use targets,
reducing system water loss, eliminating
clearly wasteful practices, and
strengthening urban drought contingency
plans. These measures aim to not only
reduce immediate water use but to establish a long-term change in the way Californians think about
water.
What a Difference a Year Makes – For California and San Luis Obispo
The California Department of Water Resources Water Year 2017 report, subtitled “What a Difference a
Year Makes,” noted that the water year “dramatically illustrated the variability in California’s annual
precipitation, ending the state’s 5-year drought and coming in at second place for statewide runoff, behind
the wettest year of 1983.” On the hydrologic impacts of a wet 2017, the statewide report states:
Many of the hydrologic impacts of California’s prior five-year drought were remedied by the wet
conditions. For the first time since 2011, runoff in major river basins exceeded 150 percent of
average, in some cases exceeding 200 percent of average. The abundant runoff replenished
depleted soil moisture. Depleted surface water storage in most of the state’s major res ervoirs was
refilled (excepting Lake Oroville, due to emergency repairs and reconstruction of its spillways).
Locally, the City saw its surface water reservoirs recover between January and June of 2017. Since the end
of the drought the City has seen a slight increase in overall consumption from 2016 to 2017, from 92
gallons per capita day (gpcd) in Water Year 2016 to 95 gpcd in Water Year 2017. For potable water only,
the increase was from 88 gpcd in Water Year 2016 to 91 gpcd in Water Year 2017.
This conservation measure that originated with the drought became a
permanent requirement under the 2016 Executive Order
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Water Resiliency Planning
The City declared Climate Action a top priority during its January 2017 major city goal-setting workshop
and identified objectives focused on energy efficiency and greenhouse gas reductions within City facilities,
such as the City’s Water Treatment Plant. The City is in the study phase of an energy efficiency project at
the Water Treatment Plant to utilize photovoltaic panels and install a hydropower turbine that would
convert the energy in the high-pressure water line from Nacimiento Reservoir into electricity. The
electricity generated on-site would offset the Water Treatment Plant’s overall power demand.
Concurrently, the energy efficiency project will assess several projects identified in the adopted 2015
Potable Water Master Plan such as: pump efficiencies within plant, the primary disinfection system, water
quality in storage tanks, distribution main inter-ties between service zones, and settings of related
controls needed for control system (SCADA-Supervisory Control and Data Acquisition) integration. The
assessment will make recommendations to replace aging infrastructure in a holistic manner from the
surface water source, to the treatment plant, and within the distribution system.
Although it is not clear exactly how San Luis Obispo and its watersheds will be affected, climate change
will impact future water supplies. To ensure water supply resiliency under worse-case scenarios, the City
utilizes a multi-source water supply discussed further in this report, makes conservative water demand
projections, and continues to pursue increased water use efficiency, increased water recycling, and
groundwater recharge.
Formula for Water Resiliency
Multi-
Source
Water
Supply
Conservative
Water
Demand
Projections
Water Use
Efficiency
Water
Recycling
Future
Ground
Water
Recharge
Water
Resiliency
10%32%25%
100%79%78%
SALINAS RESERVOIR WHALE ROCK RESERVOIR NACIMIENTO RESERVOIR
LOCAL RESERVOIR LEVELS
Jan-17 Jun-17
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Water Loss Audit Regulation
Even the most efficiently managed water systems across the country experience unavoidable water loss
from leaks, water main breaks, meter inaccuracies, and a variety of other causes. Despite efforts to
minimize water loss, according to the US Environmental Protection Agency, the average water system
sees a difference of about 15 percent between water produced and water sold each year. The City is
working to reduce both real and apparent water losses. Senate Bill 555, approved by Governor Brown in
October 2015, requires retail water suppliers in California with 3,000 or more connections, or an annual
water demand of over 3,000 acre-feet, to conduct an annual audit of their distribution system to quantify
water loss. The standardized audit must be validated by a certified third party to ensure data accuracy
and consistency in reporting. The City submitted its first annual water loss audit to the Department of
Water Resources in October 2017
Calendar Year 2016 Water Loss
Apparent Losses 102.8 AF
Real Losses 412.9 AF
Water Losses 515.7 AF
Non-revenue water as percent by volume of water supplied 11.7%
Non-revenue water as percent by cost of operating system 2.8%
By “benchmarking” this data and setting water loss efficiency goals, the City will continue to work to
reduce real and apparent water losses by:
✓ Installing a computer system to monitor water system data such as pressure, flow, and tank levels
for early detection of abnormalities in the water distribution system.
✓ 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.
✓ Implementing a comprehensive meter replacement strategy to ensure water used at homes and
businesses is correctly recorded.
✓ Performing routine billing audits to reduce data handling errors.
Sustainable Groundwater Management Act and Formation of a Groundwater Sustainability Agency
The Sustainable Groundwater Management Act (SGMA) is a statewide law that empowers local agencies
to adopt groundwater management plans that relate to the needs and resources of their communities.
Although currently banking its groundwater resources, the City envisions groundwater playing an
important role in ensuring continued resiliency in its water supply portfolio.
During the 2017 Water Year, the City became a Groundwater Sustainability Agency over the area of the
San Luis Obispo Valley Groundwater Basin that lies beneath and within its jurisdictional boundaries. The
San Luis Obispo Valley Groundwater Basin “eligible entities” (City, County, Golden State Water Company,
Edna Ranch Mutual Water Company-East, Varian Ranch Mutual Water Company, and Edna Valley Growers
Mutual Water Company) are all working collaboratively to comply with SGMA requirements for the entire
Real Water Loss
Leaks in distribution system
infrastructure, pipeline breaks,
and water tank overflows.
+
Apparent Water Loss
Unauthorized consumption (water
theft), water metering inaccuracies,
and data handling errors.
=
Total
Water
Loss
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groundwater basin. The GSA structure includes a Groundwater Sustainability Commission which is an
advisory body to the City Council and the Board of Supervisors. The Groundwater Sustainability
Commission consists of one member from the City Council, one County Supervisor and a representative
of each of the identified water companies. The City, County, and eligible entities are required by SGMA to
work together to create Groundwater Sustainability Plans by January 31, 2022.
II. WATER SUPPLY
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. The City has four primary water supply sources including
Whale Rock Reservoir, Salinas Reservoir, Nacimiento Reservoir, and
supplies recycled water for landscape irrigation and construction water.
Groundwater serves as a fifth supplemental source. The supply per
source for Water Year 2017 (October 1, 2016 to September 30, 2017) is
summarized below.
2017 City Water Supply by Source (Acre Feet)
Nacimiento
Reservoir
Whale Rock
Reservoir 2
Recycled
Water
Salinas
Reservoir Groundwater 3 Total City Water
Demand
3,383 1,150 229 213 0 4,975
68% 23% 5% 4% 0 % 100%
Notes:
1. All values are rounded.
2. Water delivered to Cal Poly State University is excluded from the City’s water demand.
3. Groundwater was not used for potable purposes during the 2017 Water Year.
NACIMIENTO RESERVOIR
Water deliveries to the City from Nacimiento Reservoir began in January 2011. During the 2017 Water
Year, 68 percent of the City’s total water demand was met by Nacimiento Reservoir. San Luis Obispo
County operates and maintains the water delivery system from Nacimiento Reservoir to participating
agencies (currently the cities of Paso Robles and San Luis Obispo, Atascadero Mutual Water Company,
Templeton Community Services District, County Service Area 10A [Cayucos], Santa Margarita Ranch, and
Bella Vista Mobile Home Park). The Nacimiento Project Commission provides oversight to project
operations, maintenance, and the project budget. The Nacimiento Project Commission is made up of
representatives from each of the four agencies’ governing boards and a County Representative who is a
member of the County Board of Supervisors which also sits as the Board of Directors for the Flood Control
District.
Since 2010, San Luis Obispo County Flood Control
District, the Nacimiento Regional Water
Management Advisory Committee, Monterey
County Parks, and Monterey County Water
Resources Agency have worked together to plan,
advise, and organize a Mussel Prevention
Program at Lake Nacimiento. On July 29, 2017, an
inspector noticed hundreds of invasive mussels
attached to a boat and prevented the owner
City of San Luis Obispo
Water Supply Sources
✓ Nacimiento Reservoir
✓ Whale Rock Reservoir
✓ Recycled Water
✓ Salinas Reservoir
✓ Groundwater
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from launching at the Heritage Ranch boat ramp. Inspections are conducted as part of the on-going
program. Invasive mussels have not been found in any local San Luis Obispo County lakes to-date, due in
part to inspection program efforts, along with responsible boat owners’ prevention efforts.
SALINAS & WHALE ROCK RESERVOIRS
Prior to receiving water from Nacimiento Reservoir, Salinas and Whale Rock Reservoirs served as the City’s
primary water supplies for over 50 years. The City pays the County of San Luis Obispo Flood Control and
Water Conservation District (County) to provide oversight, operations, and maintenance of the Salinas
Reservoir and related water delivery facilities. The City provides the oversight, operations, and
maintenance of the Whale Rock Reservoir for the benefit of the Whale Rock Commission, a joint powers
agency made up of Cal Poly State University, California Men’s Colony, and the City. During the 2017 Water
Year, the City utilized 1,373-acre feet from Salinas and Whale Rock reservoirs, meeting 27 percent of total
City water demand.
Safe Annual Yield Update
Safe annual yield analyses of available water supply
sources are based on rainfall, evaporation, and
stream flow experienced during a historical period.
Although future conditions are unlikely to occur in
the precise sequence and magnitudes as have
occurred historically, this technique provides a
conservative estimate of the future water supply
capability of the existing sources, and provides a
tool for observing the impacts of increased
temperature, evaporation, and decreased
precipitation.
In 1988, the City contracted with engineering firm
Leedshill-Herkenhoff, Inc., to prepare a detailed
analysis of the coordinated operation of Salinas and
Whale Rock Reservoirs and create a model to
determine the safe annual yield. The report was completed in 1989 and utilized data from 1943 through
1991 including drought periods in 1946-51, 1959-61, and 1976-77. Key assumptions used in the model
were that the "controlling drought period" was from 1946 to 1951, that the City only used Whale Rock
Reservoir when Salinas Reservoir was below minimum pool or could not meet the City’s monthly demand,
and that minimum pool at Salinas and Whale Rock of 400 and 500 acre-feet, respectively. The minimum
pool at each lake is the amount of water that must be left in the lake for fishery and habitat resources (in
2017, minimum pool for each lake is 2,000-acre feet). Under those assumptions, the study estimated the
City’s total safe annual yield from the two reservoirs to be 9,080 acre-feet per year.
In 1991, staff updated the safe annual yield model to examine the impact of the 1986-91 drought and
revise the assumptions on the amount of water used from Whale Rock Reservoir each year to more
accurately reflect the way the City used that resource. The analysis determined that the 1986-91 drought
was the critical drought of record for the two reservoirs. When siltation is included, these revised
assumptions resulted in a reduction in the safe annual yield estimate to the 6,940-acre feet recognized
today.
The most recent drought data is currently being analyzed and peer-reviewed to determine if reductions
to the City’s current safe annual yield will be necessary going forward. Reductions are anticipated as the
Whale Rock Reservoir Level Gauge.
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recent drought is now the critical drought of record. Revisiting the safe annual yield model will also
consider revision to the assumptions on the amount of water used from Salinas and Whale Rock
Reservoirs each year to accurately reflect the way the City uses its available water resources.
Spillway Assessment
As a result of the spillway failure at Oroville Dam, the
Department of Water Resources (DWR) is requiring
detailed analyses of dams that have large spillways
at high hazard dams. Though there are no known
deficiencies in the Whale Rock spillway, in May 2017,
the City received a letter from the DWR requesting
preparation of a work plan for a comprehensive
spillway condition assessment by August 1, 2017. By
conducting an analysis of design, current conditions,
and underlying or adjacent geology, any deficiencies
in the spillway will be identified. If required,
corrective action will be planned and projects
implemented to ensure the ability of Whale Rock
Reservoir’s spillway to function as designed.
The Work Plan for Whale Rock Reservoir’s Comprehensive Spillway Condition Assessment was approved
in September. The intent of the assessment is to evaluate the ability of the spillway to function as intended
during normal operations as well as during a flood event. The tasks listed in the work plan include:
• Review of the spillway’s design features using available as-built drawings, design and
construction records
• Evaluation of the existing conditions of the spillway
• Geologic inspection
• Evaluation of all inspection and repair records
The City’s Utilities Department staff is developing a scope of work for the comprehensive spillway analysis
based on the approved Work Plan. The scope of work will be the basis for a request for proposals to
identify qualified consultants to perform the spillway analysis.
Pipeline Reliability Analysis
The 18-mile long Whale Rock pipeline was
constructed in the late 1950s and has served the City
well since 1960, requiring minimal maintenance and
repairs. A pipeline reliability analysis was prioritized
as part of the Whale Rock Reservoir capital
improvement program for 2017-19. The analysis is
expected to be completed during the 2018 Water
Year. By determining the true condition of the
pipeline utilizing modern technology, it is expected
the Whale Rock Commission will be able to focus
resources on needed point repairs to the pipeline
and avoid full-scale replacement based on pipe age.
Whale Rock Reservoir Spillway
30-inch Whale Rock Pipeline Repair Conducted in June 2017
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RECYCLED WATER
For the 2017 Water Year, the City delivered 229-acre
feet of recycled water, up from 202-acre feet for the
2016 Water Year. The City Council adopted a
resolution approving the 2017 Recycled Water
Master Plan on March 21, 2017 and authorized staff
to negotiate an agreement for delivery of recycled
water outside the city limits consistent with policies
and findings identified in the City’s General Plan.
The design phase for the City’s Water Resource
Recovery Facility (WRRF) Project continued through
Water Year 2017. Construction is planned to begin in
October 2018 and continue through 2021. When
complete, the WRRF Project will maximize recycled
water production. The project will also enable the City
to consider potable reuse, part of a One Water
concept, in the future.
As part of a larger property upgrade, the Irish Hills
Hamlet, a 146-unit apartment complex on Los Osos
Valley Road originally constructed in the 1970s,
retrofitted its landscape and irrigation system to
utilize recycled water. The property has almost
76,000 square feet of landscaped area and is
estimated to offset five-acre feet of potable water use
with the retrofit.
GROUNDWATER
The City stopped using groundwater for potable purposes in April 2015. The City’s groundwater wells
remain in an operable, stand-by position should the use of groundwater be required. During the 2017
Water Year, the City continued its work with a hydrogeologist to site a future well field for a potential
groundwater program expansion.
III. WATER DEMAND
During Water Year 2017, 67 percent of total water use in the City was to support single and multi-family
residential uses, 25 percent was to support commercial and other non-residential development, and eight
percent was to support landscape irrigation (separately metered). Historical water use is summarized
below, as well as corresponding population, per capita use rate, and precipitation. The 2017 per capita
water use was 95 gallons per capita per day (gpcd). Based on the City’s General Plan Water and
Wastewater Management Element policies, the City uses 117 gpcd to project water required to serve
build-out population.
Irish Hills Hamlet became the City’s latest recycled water
customer in August 2017
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Population, Water Use & Rainfall
Year Population Total Water Use
(acre feet)
Per Capita
Water Use
(gpcd)
Rainfall1,2,3
(inches)
2008 44,579 6,359 127 18.1
2009 44,829 6,134 122 18.9
2010 44,948 5,489 109 36.0
2011 45,418 5,285 104 18.9
2012 45,308 5,541 109 21.5
2013 45,541 5,892 116 3.8
2014 45,473 5,524 109 14.2
2015 45,802 4,990 97 11.8
2016 46,117 4,731 92 17.8
2017 46,724 4 4,975 95 35.1
Notes:
1. Rainfall amounts fo r 2005 –2012 calendar year source: Cal Poly CIMIS Weath er Stati on.
2. Rainfall amount fo r calendar year 2013-2015: SLO Reservoir.
3. Data for 2008 through 2014 presents calendar year rainfall data. 2015 and 2016 rainfall data covers the Water Year
(October through September).
4. http://www.dof.ca.gov/Forecasting/Demographics/Estimates/e-1/
As the City’s reservoirs are located in different watersheds,
described below, rainfall at various sites within San Luis
Obispo County benefits us. All locations exceeded the annual
average during the 2017 water year.
2017 Water Year Rainfall Totals
Rainfall
Measurement
Location
Watershed
Annual
Average
Rainfall
(in inches)
2017 Water
Year Total
Rainfall
(in inches)
Rocky Butte Nacimiento
Reservoir 39 87.1
Hwy 46 and W
7 Mile Road in
Cambria, CA
Whale
Rock
Reservoir
30 38.0
SLO Reservoir City 25 35.1
Salinas Dam Salinas
Reservoir 23 33.6
Source: http://www.slocountywater.org/site/Water%20Resources/Data/
maps/precipitation-real-time.htm
San Luis Obispo and surrounding watersheds
experienced impressive rainfall totals during the
2017 Water Year
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IV. WATER RESOURCE AVAILABILITY
The following table summarizes the Water Resource Availability based on Water and Wastewater
Management Element, Section 3. Water availability for 2017 is 12,115-acre feet, an increase of six-acre
feet over 2016 due to increased recycled water usage.
2017 Water Resource Availability
Water Resource Acre Feet Description
Salinas & Whale Rock Reservoirs 6,940 Safe Annual Yield 1
Nacimiento Reservoir 5,482 Dependable Yield 2
Recycled Water 193 2016 Annual Usage 3
Siltation from 2010 to 2060 (500) WWME Policy A 4.2.2 4
12,115 2017 Annual Availability
NOTES:
1. Safe Annual Yield determined from computer model, which accounts for siltation loss
through 2010 (per WWME Policy A 4.2.1).
2. Dependable Yield is the contractual amount of water the City has rights to from
Nacimiento Reservoir.
3. The quantity of recycled water included is the actual prior year’s recycled water usage
(calendar year 2016) 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.
V. WATER SUPPLY ACCOUNTING
Per General Plan Water and Wastewater Management
Element, Section 5, the City accounts for water supplies
necessary to meet three specific community needs:
• Primary water supply
• Reliability reserve
• Secondary water supply
The City’s primary water supply is defined as the amount
of water needed to serve the build-out population
identified in the General Plan, Land Use Element (2014).
Table 3 in the Land Use Element identifies an urban reserve
capacity of 57,200 people. The quantity of water needed
for the primary water supply is calculated per WWME
Policy A 5.2.2, using 117 gallons per capita per day (gpcd).
The reliability reserve provides a buffer for future
unforeseen or unpredictable long-term impacts to the
City’s water supply. The quantity of water for the reliability
reserve is established using 20 percent of the existing City
population (46,724, 2017 population) at 117 gpcd, thus the
reliability reserve will increase over time as population
increases. The reliability reserve concept is included in the
Primary Water Supply
= 117 gpcd x City Build-out Population
= 117 gpcd x 57,200 x 365 day/year x
Acre-Ft/325,851 gal
7,496 Acre-Ft/year
Reliability Reserve
= 117 gpcd x City Population x 20%
= 117 gpcd x 46,724 x 365 day/year x
Acre-Ft/325,851 gal x 20%
1,225 Acre-Ft/year
Secondary Water Supply
= Current Annual Availability – Primary
Water Supply – Reliability Reserve
= 12,115 Acre-Ft/year A – 7,496 Acre-
Ft/year – 1,225 Acre-Ft/year
3,394 Acre-Ft/year
A 2017 Annual Availability
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City’s Charter (Section 909) which identifies that the water may not be used to serve future development,
and is defined per WWME Policy A 5.2.3.
The City’s secondary water supply is the amount of water remaining from available water resources above
those needed to meet the primary water supply and reliability reserve. The secondary supply is identified
to meet peak water demand periods or short-term loss of City water supply sources, per General Plan
Water and Wastewater Management Element, Policy A 5.2.4. Water supply accounting is summarized in
the table below .
2017 Water Supply Accounting (acre feet)
Total Primary Water Supply Reliability Reserve Secondary Water Supply
12,115 7,496 1,225 3,394
VI. WATER DEMAND MANAGEMENT
The water conservation program is an integral part of the City’s overall water management strategy. In
the late 1980’s, the City implemented effective water efficiency programs and policies that allowed for
continued community growth and economic development during water-constrained periods. It is
estimated that 90 percent of residential toilets in the City have been retrofitted to 1.6 gallons per flush or
more efficient. The City’s Toilet Retrofit Program is still active, requiring replacement of inefficient toilets
upon change of ownership of a home. Through strong conservation efforts, the community has reduced
its annual average per capita water use from over 180 gallons in 1987 to 95 for the 2017 Water Year.
To reach all local demographics, outreach efforts
were expanded by attending local events such as
Farmers Market, Earth Day, and the Disaster
Preparedness Expo. Conservation messaging also
continued through traditional media sources as well
as new avenues such as on-line “How To” videos
available at the City’s website (slowater.org)
explaining common areas around the house where
leaks occur and unnecessarily consume water.
During the 2017 Water Year, the City’s Water Efficient
Landscape Ordinance was updated with new climate
data which reduced the acceptable amount of
irrigation demand at newly constructed and
landscaped properties.
REGIONAL WATER RESOURCE PLANNING
The City continues to participate as a member of the Water Resources Advisory Committee and Regional
Water Management Group, which promotes collaborative, integrated management of water resources
within San Luis Obispo County and provides policy recommendations to the County Board of Supervisors.
In addition, the City participates in the regional Partners in Water Conservation group which is made up
of water conservation professionals from local agencies. The group meets every other month to discuss
trends in the industry, upcoming changes to regulations, and to work together on regional messaging
related to water conservation and water use efficiency.
Utilities Department information booth at 2017 Disaster
Preparedness Expo.
Packet Pg 166
10