Urban water use is generally determined by population, its geographic location, and the percentage of water used in a community by residences, industry, government, and commercial enterprises. It also includes water that cannot be accounted for because of distribution system losses, fire protection, or unauthorized uses. For the past two decades, urban per capita water use has leveled off in most areas of the State. The implementation of local water conservation programs and current housing development trends, such as increased multiple-family dwellings and reduced lot sizes, have actually lowered per capita water use in some areas of the State. However, gross urban water demands continue to grow because of significant population increases and the establishment of urban centers in the warmer interior areas of the State. Even with the implementation of aggressive water conservation programs, urban water demand in California is expected to grow in conjunction with increases in population.
Estimates of urban water use in this update of the California Water Plan are based on population and per capita water use values. per capita values, called unit use values, are estimated from water production and delivery records provided by urban water purveyors. The gross per capita use was divided into residential, commercial, industrial, governmental, and unaccounted categories, and the percentage of total water use represented by each category was calculated. In most cases, the gross per capita water use numbers presented need to be interpreted carefully because high-water-using industries and commercial enterprises can skew the figures. For example, a high-water-using paper pulp mill on the North Coast can double the gross per capita water use for that area. Furthermore, per capita water use values can mask effects of drought, conservation, inland growth, changes in industry, and other factors affecting water use simultaneously.
This chapter presents factors affecting urban water use, including population growth, urban land use, water conservation, and pricing, as well as presenting urban water use forecasts to 2020.
Population growth now exceeds projections made in the 1980s and has continued into the 1990s despite the recent economic recession. Although several entities forecast population growth, State law requires that the Department of Water Resources use Department of Finance population projections for planning purposes. Forecasts of urban water use in this bulletin are based on Department of Finance's Population Projections by Race/Ethnicity for California and Its Counties, 1990-2040, Report 93 P-1. Figure 6-1 compares population projections from prior water plan updates. DOF projections use a baseline cohort-component method to project population with assumptions as to future birth rates, death rates, and net migration. Trends based on population estimates back to 1960 were used to calculate the projections reported here. DOF projections at the county level were used as the control for all DWR projections. Only some Northern California coastal counties, such as San Francisco and Marin, are projected to have little or no growth out to 2020. The 1990 through 2020 population figures, by hydrologic region, are shown in Table 6-1.
For a comparison of projections, Figure 6-2 compares DOF projections to those of the following:
Accompanying the growth in population has been a dramatic increase in urban land use (acreage). Trends in urban land use can cause significant changes in urban per capita water use. For example, smaller lot sizes and increased multi-family housing generally lower per capita water use. Also, increased plantings of low-water-using landscapes and more efficient watering tend to push per capita water use down. However, water conservation efforts have only managed to slow increases in the applied urban water demand because of significant population increases and growth in the State's warmer interior. Based on DWR land use surveys conducted during the 1980s, there are now 3.75 million urban acres in California. Table 6-2 compares California's overall population density with New York, Texas, Florida, and countries with similar levels of industrial development.
With regard to the urbanization of agricultural lands, the Department of Conservation has estimated that nearly 310,000 acres were developed and urbanized between 1984 and 1990. Of this land, 63,400 acres were formerly irrigated farmland, over one-half of which was considered prime farmland, according to the U.S. Department of Agriculture's Land Inventory and Monitoring System as modified for California.
Urban water conservation efforts have been expanding since the 1970s. Unlike agriculture, organizations such as the University of California Cooperative Extension and local Resource Conservation Districts did not exist to provide conservation expertise to urban water users. Urban water agencies have now filled that void and are dramatically increasing water conservation programs. DWR's Water Conservation Office works cooperatively with local water agencies on many conservation efforts such as leak detection, plumbing code changes, conservation planning, efficient landscape ordinances, and Best Management Practices. DWR's Water Education Office, with assistance from district offices, is working with local agencies to develop and implement water education programs.
With the passage of the Urban Water Management Planning Act in 1983, the California Legislature acknowledged the importance of water conservation and demand management as essential components of water planning. The act requires the 300 medium-sized and large urban water agencies to prepare and adopt plans for the efficient use of their water supplies and update those plans every five years. The first plans were due in 1985. Over 95 percent of the agencies affected by the law submitted a plan.
In 1988, during the Bay-Delta Proceedings, interested parties gave the State Water Resources Control Board widely divergent opinions on appropriate levels for implementing urban conservation measures. To resolve these differences, urban water agencies, environmental groups, and State agencies actively participated in a three-year effort which resulted in identifying Best Management Practices. These are conservation measures that meet either of the following criteria:
Sixteen initial BMPs that meet at least one of these criteria have been identified. Table 6-3 lists the practices and indicates those that have been quantified. Several additional practices that may meet the criteria are under study as Potential Best Management Practices. The Potential BMPs have not been used in estimating future urban water demand, but are discussed more fully in the last section of this chapter.
As of December 1992, over 100 water agencies, plus over 50 public advocacy groups and other interested parties, had signed a Memorandum of Understanding Regarding Urban Water Conservation in California. This MOU commits signatories to implement these BMPs at specified levels of effort over the period 1991 to 2001. The water industry and others are working toward the implementation of BMPs through the California Urban Water Conservation Council, established under the MOU. Full descriptions of BMPs, including estimates of savings and implementation schedules, are contained in the MOU.
The widespread acceptance of BMPs in California virtually assures that their implementation will become the industry standard for water conservation programs through 2001 and probably beyond. The BMP process offers great advantages for water agencies. There will be significant opportunities to combine programs on a regional basis to reduce implementation costs and increase effectiveness. In addition to the programs described above, many of the cooperative efforts to help local agencies with urban water conservation programs will focus on implementing BMPs.
Water conservation will undoubtedly continue to play a significant role in managing California's urban water needs. Proven conservation measures will be implemented by more agencies, and new measures will gain greater acceptance. More sophisticated economic analyses will shape the ways that water needs are met or modified. However, as water use continues to become more efficient, agencies will lose flexibility in dealing with shortages.
Many water conservation specialists think conservation encouraged by water pricing is one of the most important BMPs for reducing urban water use. Many factors influence the water prices levied by urban water agencies. Some of the major ones include the source of the water, methods of transporting and treating it, the intended use, the pricing policies and size of water agencies, and climatic conditions.
The costs of supplying water depend greatly on the source and use of the water. For example, the cost of diverting water from a river and using it on adjacent land can be less than $5 an acre-foot; in contrast, the cost of sea water desalination can exceed $2,000 an acre-foot. Other significant factors influencing the cost of water supplies is the distance the water must be transported from the source to its ultimate place of use and the level of water treatment required to make it usable. For example, the State Water Project delivers supplies both in Northern and Southern California and contracting water agencies must pay the full cost of supply and delivery to their area. Supplies delivered to Southern California must travel through hundreds of miles of aqueducts and be pumped over a mountain range before reaching their final destination. As a result, the costs of these supplies are greater than those delivered farther north because of increased transportation costs. The pricing scheme is much like that of train tickets; for example, the farther you travel, the higher the price of the ticket.
If an agency serves a heavily populated area with a large number of connections per square mile, the average fixed costs and some variable energy costs of serving each customer will tend to be less. Conversely, if the agency serves a sparsely populated area, the average fixed costs of serving each customer are normally higher.
Generally, supplies used for urban purposes cost more than those used for agriculture because urban supply systems are more complex and often involve costly local facilities for system regulation, pressurization, treatment plants, distribution systems, water meters, and system operation (including meter reading and customer billing). In addition, some water rates include costs for waste water treatment. Further, future increased treatment costs could add another $1,000 per acre-foot to urban water costs. However, agricultural water costs are typically assessed at the farm headgate or edge of the property. The rates charged for water supplied to agricultural users do not include the costs incurred by a farmer for labor and equipment to distribute water supplies throughout a farm. These costs often incorporate land preparation, specialized machinery, and complex distribution through canals, pipes, or drip lines.
The policies adopted by various water agencies also significantly affect the final prices consumers pay. For example, some agencies use water rates to fully recover the costs of acquiring and delivering supplies, whereas others use a combination of water rates and local property taxes. Policies concerning the use of water meters and rate structure are also important. Although most urban retail agencies in California use meters to monitor customer use and to levy charges, some (mainly in the Central Valley) do not. Typically, the costs to consumers of using unmetered supplies (with flat rate water charges) are less than if those same supplies were metered. However, in times of drought when water use is reduced, water agencies that have flat rates (water charges independent of use) are not affected by reduced revenues to cover fixed costs.
Where supplies are metered, rate structure becomes important. For example, most agencies have switched from declining block rates (where unit water costs decrease with increasing usage) to either constant or increasing block rates. These rates encourage water conservation. Figure 6-3 shows some of the common urban rate structures.
During years of normal or above-normal precipitation, most agencies' supplies are adequate to meet current demands, and rates remain stable. During droughts, the rates water agencies charge vary depending on reliability and availability of supplies. For example, during the 1987-92 drought, many water purveyors adopted higher rates to encourage water conservation. Several even implemented drought penalty rates designed to drastically reduce water use. These policies reduced water use; however, an unwanted consequence of reduced water use was reduced revenues to the agencies, which still had to pay their system's fixed costs plus the costs of expanded conservation programs. To remain solvent, many water agencies had to increase rates several times during the drought.
The following two subsections discuss urban retail water costs and urban ground water costs. They are presented to illustrate the complexities of urban water pricing and the vast differences in cost to various communities in California.
Urban retail water prices vary greatly because of the large number of agencies with different production costs and pricing policies throughout the State. Each agency is likely to have different pricing policies for the different customer classes, such as residential, commercial, and industrial. Water rates and profit margins of investor-owned utilities in California are regulated by the Public Utilities Commission.
Table 6-4 summarizes 1991 single-family residential monthly use and retail water cost information for selected cities. Some of the higher water bills are found in cities along the coast (such as Corte Madera, Santa Barbara, Goleta, and Oceanside). Some of the lower bills are found in the cities in the Central Valley (such as Sacramento and Fresno). Many of these 1991 water costs are higher than they were prior to the 1987-92 drought.
Table 6-5 summarizes 1991 commercial and industrial water use and cost information for selected cities. Unlike Table 6-4, Table 6-5 does not identify summer and winter uses and costs. Instead, it displays an average monthly use. Single-family residential customers, as a group, tend to have similar unit water uses, which is not the case for commercial or industrial customers. It is difficult to define a typical commercial or industrial customer, particularly in the industrial sector, which can include bakeries as well as oil refineries. Commercial and industrial water costs were based upon a two-inch meter size. The table shows that some of the higher commercial and industrial water costs are also found along the coast. Some of the lower costs are found in the Central Valley. Again, the drought may be have increased these 1991 water costs.
Definitive conclusions concerning water uses and costs among cities cannot be derived solely from these two tables because of the many complex factors influencing water prices, including proximity to supply and the level of treatment required.
Local water agencies provide supplies to most residential and commercial customers in California. Within the industrial sector, small manufacturing firms also obtain supplies mainly from water agencies. However, many large, water-intensive, manufacturing firms (such as refineries and chemical manufacturers) have developed their own ground water supplies.
Ground water costs vary widely throughout the State. Many factors influence these costs, including depth to ground water, electricity rates, pump efficiencies, and treatment requirements. Another factor was the prolonged drought, which resulted in lower ground water levels and higher pumping costs. Typically, self-provided ground water costs are less than the costs of treated surface water. Table 6-6 presents ranges of urban ground water costs for the hydrologic regions. These costs include capital, operations (including pumping energy costs), maintenance, replacement, and treatment costs.
From the beginning of this century to 1970, urban per capita water use increased steadily, as illustrated by Figure 6-4, which charts increases in per capita water use in the San Francisco Bay area. Since 1970, however, the per capita use has been fluctuating but no longer shows a steady increase in most areas of the State, as shown in Figure 6-5, Urban Per Capita Water Use, 1940-1990. Large reductions in per-capita water use are pronounced during drought years when aggressive short-term conservation and rationing programs are in effect. In the long term, permanent water conservation programs and other factors have begun to reduce overall per capita water use in some areas.
Other factors tend to raise per capita unit use rates, thus making it difficult to analyze trends. Climatic variations affect water use significantly from one year to the next. In the long term, fewer people per household, increases in household income, and population growth in warmer inland areas have tended to counteract the effects of multifamily housing and conservation, which drive per capita water use downward. Figure 6-6 compares the gross average per capita water use in selected California communities from 1980 to 1990. Gross per capita use rates are higher in many hydrologic regions because of large industrial or commercial enterprises combined with low resident populations. For example, there are high per capita water use rates in the Colorado River Region because of tourist populations and a predominance of golf courses.
Even with effective drought emergency measures, drier winters tend to cause an increase in water use for landscape irrigation (to replace effective precipitation) during the winter. The average per capita monthly water use, statewide, during the 1987-92 drought, in relation to the rest of the 1980s, illustrates this fact (Figure 6-7).
The gross per capita water use values previously cited can be separated into the four categories of use: residential, commercial, industrial, and governmental. Percentages of total urban water use have been estimated for these four sectors for 1990 and compared with 1980 in Figure 6-8. The biggest difference is in industrial water use. The decline in industrial water use results from conservation and water reuse undertaken in that sector, as well as the closure of some high-water-using industries, such as lumber mills and canneries. Waste water discharge requirements have caused many industries to recycle their water to avoid the costly water treatment required for discharge.
Residential water use averages about 120 gallons per capita per day in California. Overall interior water use has remained near 80 gallons per capita per day on the average during the 1980s. However, these per capita figures can vary significantly due to household income and single-family or multifamily households. Table 6-7shows the breakdown of in-door water use into its components. Exterior water use is extremely variable, ranging from 30 percent of residential use in coastal areas up to 60 percent in hot inland areas.
The 1990 level was normalized using per capita water use values based on an average of 1980 to 1987 per capita use of more than 130 California communities. This "normalization" for the 1990 level was achieved by using water use data not affected by the 1987-92 drought. Those drought years were affected by rationing and mandatory conservation programs. The averages also include estimates of self-supplied (not delivered by water purveyors) ground and surface water. These values were then weighted by population to yield the gallons per capita daily use by region as displayed in Table 6-8. Incorporated in these values are reductions in per capita use, caused by conservation, that have accumulated since 1980. It is estimated that urban applied water in the normalized 1990 base-year was being reduced annually by approximately 435,000 af statewide due to on-going conservation programs as compared to 1980. This estimate did not include drought contingency programs. As mentioned earlier, these are gross per capita water use values that include the residential, commercial, industrial, and governmental sectors; the percentage of current total use for each sector is shown in Table 6-9.
The forecasted per capita use by hydrologic regions for years 2000 through 2020 shown in Table 6-8 includes estimates of the reductions in urban use caused by implementation of BMPs; these are rough estimates since the range of savings that can be expected from an individual BMP may be quite large. For this bulletin, the estimated reductions due to BMPs range from 7 to 10 percent of the forecasted per capita use, depending on the location of the area studied. The applied water reductions and the depletion reductions in 2020 due to BMPs are shown in Table 6-10. The reductions in depletions stem from reduced landscape evapotranspiration or reduced outflow to the ocean because of reduced interior water use.
The reductions in depletion are greater for coastal cities where waste water is discharged to the ocean and serves no further beneficial use. Applied water reductions in the San Francisco Bay area are all considered reductions in depletions because waste water is discharged to the ocean. In contrast, in the Sacramento River Region most excess applied water either recharges ground water basins or is returned to the river through waste water treatment facilities for later reuse downstream and thus is not a depletion. For example, the depletion resulting from net water demand in Sacramento versus that of Walnut Creek is 146 gallons per capita daily versus 184 gallons per capita daily, respectively.
Of course, the total urban applied water, net water demand, and depletions will continue to increase to 2020 because of population growth. An even greater increase is expected in drought years because of less rainfall recharging soil moisture in urban landscapes. Table 6-11 presents the estimated increases in statewide urban water demand from 1990 to 2020.
When the potential BMPs summarized in Table 6-12 are approved by the California Urban Water Conservation Council, they will be analyzed and are expected to provide some additional urban water demand reduction. For this report, the reduction in demand due to potential BMPs was not quantified. However, these potential BMPs are not expected to provide as much demand reduction as those BMPs already adopted, primarily because the potential BMPs identify few practices that affect exterior water use where the largest potential for future urban water savings exists.
Urban water agencies recognize the need for better demand forecasting methods to estimate water use. Some water agencies are moving toward a more disaggregated approach, similar to that of energy utilities. DWR and the University of California at Los Angeles have evaluated forecasting methods and developed procedures to estimate conservation from BMPs. In this approach, more data, much of which is currently unavailable or goes unreported about the end uses of water must be analyzed individually and then aggregated together to forecast overall water use. At a minimum, water use information must be known about the following categories: single-family residential; multi-family residential; commercial/institutional; industrial; and public/unaccounted. Other information on household population density, household income, and pricing structure is necessary as well. The demand must also be analyzed for winter (baseline) use and summer (peak) use. The water demand without conservation is then calculated. An expected range of demand reductions due to conservation is then estimated for each BMP. The median value of each range can be used to estimate a percentage reduction in the forecasted demand without conservation for each BMP. For many BMPs, particularly those affecting exterior water use, there are widely divergent appraisals of water savings that will need further study to improve the quality of such estimates. Specific recommendations are as follows: