By Dana Haasz

Summary: With the energy “crisis” in California, concerted efforts have been made to bring water conservation to the fore of state policies. To its credit, the state has made significant progress tackling this issue. Still, with a growing population, it has far to go to protect future water use. A recent study examined some areas yet to be maximized.

California’s history of water debates has been long and contentious, spawning best-selling books, award-winning movies and decades-long court battles. At its heart is the issue of distribution. Namely, who gets water and when. About 75 percent of the available water in the state originates in the northern third while nearly 80 percent of the demand occurs in the south. Demand peaks during the summer when natural supplies are most constrained. Extended periods of flooding and drought are a natural part of the state’s climate regime. Agriculture uses 80 percent of the water supply while urban populations are projected to increase by 15 million (45 percent) by 2020.

The supply-driven policies that dammed rivers and brought pipelines, aqueducts and reservoirs to the state allowed agriculture to develop, cities to grow and put California on the path to becoming—according to recent numbers—the fifth largest economy in the world. But today, almost every major river in California is dammed, fish and wildlife species are being driven toward extinction, habitats are being destroyed and the decision-making is increasingly fractured and divisive. It’s clear the policies that played a hand in the state’s prosperity didn’t come without their costs and aren’t up to the challenges of the 21st century.

A combination of factors, including the rise of the environmental movement and the high cost of new development projects, led to movement away from traditional sources of water and dam-building. Water managers discovered that overseeing demand offers an alternative way of augmenting supply and can help meet the pressures of a growing population in a way that’s usually more cost effective and less environmentally damaging than traditional supply-side solutions. The key to addressing problems of water use in California is understanding the potential for demand management to balance the state’s limited supply with the needs of a growing population.

Demand management
To properly incorporate demand management into planning, we need an account of how and where the state’s water is being used, as well as the economic, social and environmental attributes of water in each region. Unfortunately, the lack of adequate information has seriously inhibited this discussion. The most recent California water plan, Bulletin 160-98, prepared some basic estimates—but they were limited in scope. Consequently, there’s very little information about the potential for comprehensive demand management programs and many plausible and economically viable options continue to be omitted. Yet, this information is vital to decisions about restoring the health of the San Francisco Bay Delta, meeting our Colorado River export limitations and setting a whole range of ecological, agricultural and urban policy priorities. Without this information, questions about the state’s future industrial production, immigration reform, land use and urban growth will be much harder to answer correctly.

A Demand Side Management (DSM) study under way now aims to provide part of the missing information. The goal is to identify a broad set of possible demand management options in the urban and agricultural sectors and quantify the potential of these options for meeting current and future demands for water by increasing the efficiency and productivity of current uses. An attempt to identify and quantify all the benefits of improving efficiency wasn’t made. There are a number of related benefits that were omitted, such as reductions in wastewater costs, reductions in peak water systems loads, improved water quality and ecosystem enhancement. While these effects are all relevant and important, they’re outside the scope of the study. So far, the urban residential sector of the DSM study has been completed.

Where does it go?
Nearly 60 percent of all urban water use in California goes to meet residential needs: drinking, cooking, bathing, washing clothes and dishes, and watering gardens. Two-thirds of residential water is used inside; the remainder goes to gardens, lawns and other outdoor purposes. The residential sector is the largest urban user and studies suggest that it offers the largest volume of potential savings compared with other urban sectors. Water conservation programs that focus on the residential sector have been around in California for about two decades. In fact, many of the large agencies currently boast their residential per capita use is lower than it was in the early 1980s, mainly as a result of plumbing retrofits, education programs, water metering and water audit programs.

For the DSM study, water demand by end-use was calculated. The indoor residential end-uses examined were toilets, showerheads, washing machines, dishwashers and leaks. First, a baseline water use was established, incorporating turnover rates and replacement programs. And then, the potential water savings that could be captured was estimated, assuming existing technologies and water-efficient practices were implemented. Finally, the practices most cost-effective to implement were determined.

It was no surprise to find that conservation policies have already proven effective in reducing Californians’ demand for water. The state’s population increased by 40 percent between 1980 and 1998, but residential water demand rose by only 14 percent. It was estimated that conservation programs have already captured 750,000 acre-feet of indoor savings each year. This is enough water to meet the domestic needs of up to 6 million new residents (one acre-foot—325,851 gallons—meets the needs of about two 4-person households for one year). Showerheads and toilets have had the biggest impact on reducing water use so far; they both have legislated maximum flow rates and are generally the first end-uses of water emphasized in the program.

Just the first step
While current conservation programs provide a solid foundation, the potential for reducing demand is far from exhausted. The potential savings from installing efficient technologies are shown by end-use in Figure 1. The top line is an estimate of water use if no conservation policies or programs were implemented and per capita water demand remained constant as the population increased. The incremental savings from each end-use are subtracted from the top line, and the bottom line is water use with full adoption of efficient technologies. Although toilets have already had the single largest effect on indoor, residential demand reduction, they also hold the greatest potential for future savings because of the large number of inefficient toilets still in place. Leak reduction is another good target for agency efforts because it has so far remained virtually untapped. By 2020, the state’s population will be almost double but indoor use will actually decrease by a little over a third if smart policy choices are made. Indoor residential demand will be about 2.7 million acre-feet (MAF) by 2020 if there’s no change in current policies. If conservation became a priority while implementing all available options, that amount could decrease by about 30 percent to about 1.9 MAF.

Figure 1 here: Potential water savings by end-use

Originally, the intent was to focus solely on water saving benefits; however, energy benefits of demand-side management are also very relevant to the crisis gripping the state and an important outcome of the improved technologies. If savings from energy reductions aren’t factored into the analysis, the customer is assigned the entire cost of the device but only reaps half the benefits, resulting in unrealistic bias against improved efficiency.

The average cost of conserved water to the user for replacing each fixture under natural replacement (due to failure or remodeling) and accelerated replacement (before the end of its natural lifetime) scenarios was also examined. The results indicate that, under natural replacement, all devices are cost effective, ranging from -$300 per acre-foot for clothes washers to about $50 per acre-foot for toilets (negative values indicate savings to the customer). Under accelerated replacement, costs per acre-foot range from -$800 for showerheads, $450 for toilets, $750 for clothes washers and $6,800 for dishwashers. With the average price of water in California at about $750 per acre-foot, it was found that all devices except for dishwashers are cost effective to the consumer, even under accelerated replacement.

Landscape irrigation
The potential savings from improving landscape irrigation, which can account for up to 60 percent of household use in some areas during the dry summer months, has yet to be realized in California. In its most recent water plan, the California Department of Water Resources stated that the greatest potential reductions in urban water use would come from reducing outdoor water use for landscaping.

Estimating baseline landscape use and potential savings was trickier than the indoor analysis because of drastic variability in climate conditions throughout the state and throughout the year, the lack of data, and because landscape irrigation is very dependent on the behavior and attitudes of the individual homeowner. To address these challenges, representative landscapes of different sizes were constructed and in different climate conditions based on agency information; from this, a baseline range of water use was determined. Then, the savings potential for several water conserving measures—including maintenance, management, technological improvements and changes in vegetation—was estimated based on previous studies. For example, simple technology such as a soil probe saves about 10 percent of landscape water at a cost of about $42/acre-foot. And a recent study of evapotranspiration-based weather controllers in Irvine, Calif., yielded a 16-to-25 percent reduction in outdoor use, with an estimated cost of $207/acre-foot.

The results indicate that savings up to 60 percent are achievable through a variety of different methods. The most cost effective savings are achieved on the larger lots and are based on behavior modification rather than an overhaul of the irrigation system or landscape design. Costs per acre-foot of implementing various water conserving measures ranged from $220 to save 20 percent by installing hose timers on large, arid lots, to $2,600 for replacing existing systems with drip irrigation on small coastal lots.

Great uncertainties remain about the potential for improvements in water use efficiency in California. The magnitude of this potential depends on water prices, rate structures, technology, public opinion and policy. Despite these uncertainties, it’s clear that appropriately designed efficiency programs will generate large, cost effective improvements in water supply reliability, water quality and ecosystem health.


  1. Brickson, B, J.K. Hartshorn and E McCarthy, “Layperson’s Guide to California Water,” Water Education Foundation, 2000.
  2. Department of Water Resources, California Water Plan Update, DWR Bulletin 160-93, Sacramento, Calif., October 1994.
  3. Mayer, P., et al., “Residential End-uses of Water,” American Water Works Association Research Foundation, 1999.
  4. Seattle Public Utilities, Water Conservation Potential Assessment, Final Project Report,, 1998.
  5. Department of Water Resources, California Water Plan Update, DWR Bulletin 160-98, Sacramento, Calif., November 1998.
  6. Lessick, D., Irvine Ranch Water District, Personal communication, 1998.
  7. Hunt, T., et al., “Residential Weather-Based Irrigation Scheduling: Evidence from the Irvine ‘ET Controller’ Study,” 2001.

About the author
Dana Haasz is a research associate at the Pacific Institute for Studies in Development, Environment and Security. She holds a bachelor’s degree in geography and environmental sciences from McGill University and a master’s degree in applied geography from New Mexico State University. She can be reached at (510) 251-1600, 251-2203 (fax) or email: [email protected].


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