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USGS Water Use Data for California

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State Data
(1985-2015)

State water-use data are reported by source (surface water or groundwater, fresh and saline, and total), category, and area type (county). The water-use data presented here are the current best estimates, and may have been revised from previous publications. Data collection varied between the different compilations. Pre-1995 datasets have more data available than 2000 and later. A chart is available that provides for a conceptual picture of the changes in water-use categories between compilations.

The details of a water-use category sometimes changed between compilations. For example, for 1985-1995, thermoelectric power withdrawal data was grouped by fuel type, but for 2000-2015, thermoelectric power data was grouped by the cooling method (once-through or closed-loop).

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Introduction

The USGS's National Water Use Information Program compiles and publishes the Nation's water-use data. Public access to some of these data is provided via the USGS Water Data for the Nation site. Water use refers to water that is used for specific purposes. Water-use data are collected by area type (State, county, watershed or aquifer) and source such as rivers or groundwater, and category such as public supply or irrigation. Water-use data has been reported every five years since 1950, for years ending in "0" and "5". The USGS works in cooperation with local, State, and Federal agencies as well as academic and private organizations to collect and report total withdrawals.

Annual water-use data are expressed in units of million gallons per day (abbreviated as Mgal/d) and thousand acre-feet per year. For the irrigation category, water-use data are the average daily quantities used over a period of a year and do not represent actual daily rates. In most parts of the nation, irrigation water is applied during only a part of each year and at variable rates; therefore, the actual rate of application is much greater than the average daily rate. For all other categories, the daily quantity of water that is withdrawn may be based on daily usage or more often, monthly usage that is averaged to a daily quantity.