HomeMy WebLinkAbout06-02-2015 PH3 RitterTo:
Subject:
Mejia, Anthony
RE: Water on Lawns
From: Matt Ritter [mritter @calpoly.edu]
Sent: Friday, May 29, 2015 11:44 AM
To: Marx, Jan; Carpenter, Dan
Cc: Johnson, Derek
Subject: Water on Lawns
COUNCIL MEETING: Q _G L
ITEM NO.: _
MAY 2 9 2015
Jan and Dan,
Good to see you both yesterday. After seeing the drought contingency document for SLO city, I mentioned an
issue with two specific parts of it. One was the call for an end to lawn irrigation in certain public areas. That
needs to be considered carefully as many lawns are the likely source of water for the trees and large shrubs in or
near them trees. If lawn irrigation is stopped, trees will have to be irrigated to keep them alive. This is what we
are doing on campus.
See the attached document for more information, especially the middle of page 3 regarding the lawn issue.
The second issue is the deferment of landscape installation on new development, which should also be
considered very carefully in my opinion.
Trees are an investment, they will outlive this drought. Let's not kill them for short term savings of what
actually amounts to a small portion of the water used in California.
Best regards,
Matt
Matt Ritter, Ph.D.
Professor of Biology
mritter@calpoly.edu
Webpage
go
YCO The California Drought and
Landscape Water Use
Donald R. Hodel
Environmental Horticulture Advisor
University of California
Cooperative Extension
700 W. Main Street
Alhambra, CA 91801
drhodel @ucanr.edu
and
Dennis R. Pittenger
University of California
Cooperative Extension
Botany & Plant sciences
Batchelor Hall Extension
4114 Batchelor Hall
Riverside, CA 92521
dennis.pittenger@ucr.edu
Landscape plants (trees, shrubs, groundcovers, lawns, and flowers) and the water they
use are under unrelenting attack as the unprecedented California drought enters its fourth
year. However, most of these attacks are misguided when one looks at the facts.
The Facts about Landscape Water Use
Landscape water use in California accounts for only 9% of the total statewide water use
(Fig. 1). Yes, that's right, just 9 %. Thus, if we never watered another home or public landscape,
park, sports field, or golf course in California, the State would save 9% of its total water
consumption, which doesn't seem like much when one considers the essential functions and
innumerable benefits that landscape plants provide to enhance the quality of our lives and
make urban areas livable. To name just a few, these tree, shrubs, groundcovers, lawns, and
flowers provide:
1. Oxygen;
2. Carbon sequestration to help mitigate global warming;
3. Rain capture, dust and erosion control;
4. Shade and energy savings in heating and cooling;
5. Wildlife habitat;
6. Food;
7. Beauty and ornament;
8. Recreation;
9. Enhanced property values;
10. Psychological well- being;
11. Cultural /Historic value.
Figure 1. Average percentages of developed water use in California during a non - drought year
(Sources: Calif. Dept. of Water Resources, 2013 California Water Plan Update Chapter 3. UCLA
Institute of Environment and Sustainability, So. Calif. Environmental Report Card, Fall 2009).
6%
It o. 4% 1% :�0/�
• Agriculture
• Indoor Residential
• Outdoor Residential
Large Landscape
• Comm'I /lnst'I /lnds'I
• Other
Environmental
Of that 9% of the statewide landscape water use, residential accounts for 7% while
parks, golf courses, sports fields, and similar large landscapes account for 2 %. Landscape
irrigation is estimated to account for about 50% of annual residential water consumption
statewide. That amount varies widely from about 30% in many coastal communities to 60% or
more in many inland suburban communities.
What about Lawns?
Lawns, which have been especially singled out as water wasting culprits, are estimated
to use 40% to 60% of that 9 %, or just 3.5% to 5% of total statewide water use. Lawn grasses are
classified as either cool- season (tall fescue, Kentucky bluegrass, ryegrass, bentgrass) or warm -
season (bermudagrass, zoysiagrass, St. Augustinegrass, buffalograss) based on whether they
grow best in cooler seasons (fall to spring) or warmer seasons (spring to fall).
Cool- season grasses, of which tall fescue is the most common lawn grass, are among the
most water - demanding landscape plants. However, landscape water requirement research at
the University of California has shown that, when properly managed and irrigated, warm -
season grasses require 20% less water than that needed by tall fescue, so considerable water
can be saved without removing turf altogether. Also, the research revealed that most woody
trees, shrubs, and groundcovers, including those traditionally used in California landscapes,
perform well with 45% to 55% less water than that needed by tall fescue.
Many water conservation strategies call for an end to lawn irrigation or removing lawn
altogether. But remember that removing lawns will only bring water savings if:
1. they are replaced with no plants and the irrigation is turned off, which results in the
loss of the essential functions and benefits of landscapes; or
2. they are replaced with trees, shrubs, or groundcovers and these are cared for and
irrigated according to their requirements, which can be expensive if done well
properly.
However, if water is turned off to lawns, many trees and shrubs solely dependent on
lawn irrigation to meet their water needs will suffer, decline, and even possibly die. Declining
and dead trees are particularly hazardous because they can readily drop large limbs or even the
trunk can fail, causing serious damage to life and property. If one waters the trees that have
lawns around them, the grass will likely survive although it might be of poorer quality.
Research has clearly shown that many if not most, common trees, shrubs, and
groundcovers not traditionally considered drought tolerant or low -water use are actually very
drought tolerant once established if cared for and irrigated properly. Thus, replacing lawns or
other landscape plants with so- called drought - tolerant or low -water use plants, like desert or
Mediterranean - climate plants or California natives, is unnecessary in order to reduce a
landscape's water demands significantly and meet mandated cutbacks.
Appropriate Tree Selection, Planting, and Management Are Critical to Conserving Water
Selecting the right tree for the right situation and then planting and maintaining it
properly are critical to conserving water. Select species that are environmentally well adapted
to the site and that fit the intended use or function. Consider the ultimate height and spread of
the tree. Plant the tree correctly, at grade, and with no organic material in the backfill. Apply
and maintain 1 to 2inches of mulch. Irrigate judiciously.
What is Judicious Irrigation?
Judicious irrigation follows the principle of applying only that amount of water the tree
needs when it needs it. Simply irrigating in a judicious manner can save significant amounts of
water, and might be sufficient by itself to meet mandatory 25% to 35% water reductions
without changing the landscape to so- called "low -water use" or "drought- tolerant" plants.
Remember that most woody plants are actually drought tolerant or low -water use once
established if planted and cared for properly.
Three steps comprise judicious irrigation:
1. Goal: moisten upper 12 inches of root zone at each irrigation event.
2. When upper 12 inches of root zone reaches 50% moisture depletion (about when
the soil 1 to 2 inches deep just becomes dry), then irrigate to moisten the upper 12
3
inches of root zone. This amount is about 0.5 inch of water on a sandy soil and 1.5
inches of water on a clay soil.
3. Don't irrigate again until the upper 12 inches of root zone reaches 50% soil moisture
depletion.
These are general guidelines and they will have to be adjusted slightly to accommodate
specific sites and conditions. Also, to avoid wasteful run -off, irrigation run times to apply
sufficient water to moisten the upper 12 inches of the root zone might have to be broken up
into two or more cycles.
Three Basic Principles for Proper Landscape Irrigation
Adhere to these three general principles to reduce landscape water use:
1. Improve irrigation system performance. Fix any leaks; replace spray heads or other
non - functioning emitters; align spray heads so there is no overspray onto pavement;
clear plant material that is blocking emitters; and adjust, add, or move spray heads
so that their spray patterns overlap one another 100 %. Replace an irrigation
controller if it does not have at least three programs; four start times per program;
an offsetting that interrupts irrigation without losing the programmed settings
during a rain event; odd /even, weekly and interval program capability up to 30 days;
and a water budgeting adjustment in 10% increments.
2. Improve irrigation schedules and water management practices. Determine how
much water your irrigation system applies during a typical cycle. Run irrigation
systems between about midnight and 6:00 AM. Adjust irrigation system run times at
least monthly. Many non -turf plantings will perform acceptably if irrigation is simply
reduced 10 to 30% because landscapes are commonly over watered.
To estimate closely the amount of water your lawn and other landscape
plantings require, see the irrigation calculators under the Landscape Water
Conservation tab at www.ucannedu/cluh. Reducing lawn irrigation below the
amount estimated in the on -line calculator could result in non - optimum
performance; however, reducing the amount by 10 to 20% during the summer
should enable a lawn to survive and recover or be reseeded in the fall or following
spring if water is not restricted at that time.
3. Adjust plant care practices. Raise the lawn mowing height to at least 3 inches in tall
fescue and 1.5 inches in bermudagrass or other warm - season grasses. Avoid pruning
shrubs and trees. Fertilize lawns only moderately and generally omit fertilizing most
other plants. Apply and maintain mulch.
If additional water conservation is needed after following steps 1 through 3, then reduce
the amount of lawn to cover only the areas where the functions of a lawn are needed. Former
lawn areas can be replanted as a low -water requiring landscape, if desired, in the fall or winter
by selecting any types of woody plants or groundcovers regardless if they are labeled "native,"
"drought tolerant," or not because all woody landscape pants and groundcovers have similar
4
water demands. Maximum water savings can be achieved when former lawn areas are
converted to attractive, useful hardscape or mulched areas.
Landscape Plants and Lawns Are Worth the Water Investment
Many Californians consider public and private landscapes to be essential components
and therefore their irrigation to be a beneficial use of water, but many state and local
government and water policy leaders consider landscapes to be unnecessary or wasteful use of
water. Landscape water use research over the last 30 years has clearly shown that we can have
our landscape plants, including functional lawns, meet water reduction goals, and still have the
numerous amenities functions and quality of life benefits that landscape plants provide. In
other words, landscape plants are beneficial, justify the use of water, and a worthwhile
investment, even in this historic drought. We have the science and technology to apply only
that amount of water that plants need, no more, no less, and reap huge water savings.
Indeed, many of our colleagues in the landscape and irrigation industries have already
and for many years been using the most advanced water and irrigation science and technology
to schedule irrigations accurately to have healthy plants and still save water. It's nothing new to
us. Even our friends in agriculture, which accounts for 77% of the total amount of water used in
the State (we have to eat), have been using similar science and technology to water their crops
accurately and save water. So already and for many years, a significant portion of the plant -
based industries in California has plant -water use "down to a science," and has been saving vast
quantities of water. Others who have yet to adapt landscape water and irrigation science and
technology can "join the bandwagon" and reap similar savings.
Priorities for Landscape Irrigation in a Severe Drought
Setting priorities during times of water scarcity are crucial. Here are some to consider:
1. Ensuring that public parks, school play grounds, and sports fields have sufficient
water to maintain their landscape plantings and lawns should be a high priority.
Children and young adults need to play and exercise on grass, not asphalt or dirt,
and we all benefit from walking and exercising in a green, pastoral setting
2. Ensuring that bonafide botanical gardens and arboreta have sufficient water to
maintain their collections should also be a high priority. These institutions have
documented, curated, scientific collections of plants that have immense research
and educational value. One wouldn't turn off the fire alarm and fire suppression and
other protective systems at The Getty, so why turn off the water at a botanical
garden or arboretum? Indeed, these research collections of plants have immense
value. For example, the plant collections at the world- famous San Diego Zoo actually
have greater value than the animals. It can be argued that the value of the plant
collections at, for example, The Huntington in San Marino, is equal to if not greater
than its art or library holdings.
Water the trees. Trees form the infrastructure of our landscapes and urban forest,
and are their permanent or, at least, most long -lived and valuable components
around which the other plants intermesh, if not depend. Mature trees are among
the most valuable and difficult -to- replace plants in urban areas. Their loss would be
devastating. Trees can be likened to the steel framework of a building; how could
the building exist without it. So, keep the trees watered.
4. Limit lawns to areas that require its function as a recreational or walkable surface or
where erosion or dust control is needed. Remember that lawns are relatively easy
and inexpensive to install and established compared to woody plants and
groundcovers; thus, if severe water cuts are mandated, irrigation of functional lawns
could be greatly reduced or eliminated to allow continued irrigation of high -value
woody plants and groundcovers.
Can We Conserve Our Way Out of the Drought?
California will be unable to conserve its way out of a serious drought by trying to wring
out significant water savings from the 9% that landscape consumes in the State. Surely focusing
primarily on water conservation that targets removing all lawns and severely damaging
landscape plantings is not the answer. The official but unacknowledged statewide policy for
the past decade has been to support the water demands of population and other forms of
growth through conservation of urban landscape water use. This policy is a failed long -term
strategy, however, because the water saved in landscape irrigation has been reallocated to
meet the fundamental indoor water needs of increased population, which in turn has resulted
in a hardening of water demand because there is less and less easily conserved water in times
of drought.
Abundant, new, reliable sources of water must be found, other uses of water restricted,
and /or, when faced with projections of 10 million more people in California by 2025 (as
reported in the media recently), growth must be mitigated; yet, never have we seen controlling
growth as one of the options to address water use in this unprecedented drought. Politicians
and other leaders and officials are ignorant of the facts about the science and technology of
landscape water requirements and irrigation, and they appear to be out of touch with
Californians' quality of life requisites. Crucial public policy and decisions on water use and
distribution must be based on science, not illusion or perception.
Conclusion
In conclusion, cost /benefit analyses clearly show that landscape plants are worth the
investment in resources, especially water, even in this time of severe drought. Landscape plants
are worth having and saving. Through appropriate plant selection and proper management and
irrigation, based on the science and technology mostly developed at the University of
California, we can have our cherished landscapes, enjoy the innumerable amenities and
benefits they provide, and, yes, still save water.
R