How landscape water use stacks up in California

November 13, 2015 -  By and

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A perspective on the California drought and landscape water use.

Landscape water use in California accounts for 9 percent of the total statewide water use. Thus, if we never watered another home or public landscape, park, sports field or golf course in California, the state would save 9 percent of its average total water consumption. This does not seem like much when one considers the essential functions and innumerable benefits landscape plants provide by enhancing the quality of our lives and making urban areas livable. Trees, shrubs, groundcovers, lawns and flowers provide oxygen, carbon sequestration, rain capture, dust and erosion control, shade, energy savings in heating and cooling, wildlife habitat, recreation, enhanced property values, psychological well being and much more.

Of that 9 percent, residential use accounts for 7 percent, while parks, golf courses, sports fields and similar large landscapes account for 2 percent. Landscape irrigation is estimated to account for about half of annual residential water consumption statewide. That amount varies from about 30 percent in many coastal communities to 60 percent or more in many inland suburban communities.

Hidden costs of going dry

In addition to the amenities and benefits we would lose by letting landscapes go dry, many hidden costs are associated with this strategy. And little, if anything, is ever said about them. Letting landscapes go dry will lead to damage and even death of plants. For trees, such damage could mean dropping branches and tree failures, leading to significant property damage, human injury or death. Lawsuits would certainly follow. The risk of fires would increase, too. By changing landscapes to low-water-using plants or to nonplanted, nonirrigated areas, labor and material costs for plants, installing or retrofitting irrigation systems and other materials could be significant. Converting lawns to artificial turf is also expensive.

Lawns, which have been singled out as water-wasting culprits, are estimated to use 40 percent to 60 percent of that 9 percent, or just 3.5 percent to 5 percent of total statewide water use. Cool-season grasses, of which tall fescue is the most common turfgrass, are among the most water-demanding landscape plants. However, research at the University of California has shown that warm-season grasses require 20 percent less water, when properly managed and irrigated, than 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 percent to 55 percent less water than tall fescue.

Many water conservation strategies call for an end to lawn irrigation or removing lawns altogether. But remember that removing lawns will only bring water savings if they are replaced with: 1). no plants and turned-off irrigation, which results in the loss of the essential functions and benefits of landscapes; or 2). trees, shrubs or groundcovers. And these must be cared for and irrigated according to their requirements, which can be expensive if done properly. However, if water is turned off to lawns, many trees and shrubs solely dependent on lawn irrigation will suffer, decline and possibly die. Research has shown that many, if not most, common trees, shrubs and groundcovers not traditionally considered drought tolerant or low-water use are very drought tolerant once established—if they are cared for and irrigated properly. Thus, replacing lawns or other landscape plants with so-called drought-tolerant or low-water-use plants, like desert and Mediterranean-climate plants or California natives, is unnecessary to reduce a landscape’s water demands significantly and meet mandated cutbacks.

Can We Conserve Our Way Out of the Drought?

California will be unable to conserve its way out of a serious drought by only wringing severe water savings from the 9 percent of water that landscapes consume statewide. Focusing primarily on water conservation that targets removing all lawns and severely damaging landscape plantings is not the answer. The 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. But this policy is a failed long-term strategy 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 demands because there is less easily conserved water in times of drought.

Additional reliable sources of water must be developed, other uses of water restricted and/or, when faced with projections of 10 million more people in California by 2025, growth must be mitigated. Yet, these options have been rarely discussed or presented as long-term means to balance water supply and use in this unprecedented drought. Politicians and other leaders and officials appear ignorant of the facts about the science and technology of landscape water requirements and irrigation management, and they seem to be out of touch with Californians’ quality of life requisites. Crucial public policies and decisions on water use and distribution must be based on science, not the perception that severe limitations on landscape water use will drought-proof the state.

We argue that landscape plants are worth the investment in water even in this time of severe drought. Landscape plants are worth having and saving for a host of reasons, and irrigation to ensure their health is a beneficial use of water. Through appropriate plant selection and proper management and irrigation, we can have our cherished landscapes, enjoy the innumerable amenities and benefits they provide and still save water.

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