Planning for future urban water supply needs in California entails a wide range of efforts by local, State, and federal water agencies and other interested parties. Analysis of past water use trends is important to the effectiveness of this effort and the reliability of forecasts of water needs. The Department of Water Resources has surveyed retail water agencies and analyzed their water production data for over 35 years and has made the results available since 1968 through the Bulletin 166 series.
Bulletin 166-4 is a compilation of monthly urban water production data from nearly 300 retail water purveyors for the decade ending 1990. The data come from service areas in all 10 hydrologic regions (major water planning subdivisions) of the State. Socioeconomic and natural phenomena, notably climate, population growth, and pricing, which have influenced water use trends in the 1980s are discussed. The text also provides an analysis of urban water use by hydrologic regions and the major sectors (residential, commercial, industrial, and governmental). The urban water demands cited in the recent California Water Plan Update, Bulletin 160-93, are largely based on Bulletin 166-4 data.
The intent of Bulletin 166-4 is to provide the water community with information on the urban water use data that can be employed in statewide and regional water planning decisions. Estimates of per capita water use can indicate changes in water use patterns for a community, a region, an industry, or the State.
Bulletin 166-4 introduces the Water Savings Simulation Program, a model for urban water use forecasting developed by the Department with the University of California, Los Angeles. The Department hopes that this model will be an effective tool for planning and calculating future urban water demands.
David N. Kennedy, Director
Department of Water Resources
State of California
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