California’s water supports three main sectors: cities and communities, agriculture and environment. On average, the proportion of water used by each sector is 10 percent cities and communities, 40 percent agriculture, and 50 percent environment. This statewide ratio varies widely depending upon whether a year is wet or dry. This year, California communities were ordered to reduce their overall water use by an average of 25 percent compared to 2013. State regulators tailored mandatory cutback targets ranging from 4 percent to 36 percent for each community based on past conservation efforts.
Between 1967 and 2010, the total applied water to crops was reduced by 5 percent, from 31.2 million acre-feet to 29.6 million acre-feet (one acre foot is enough to supply all the needs of roughly two typical households for a year).
The largest share of water for environmental purposes goes to “wild and scenic” rivers, which are protected by federal and state law from dam development. That share is roughly 23 percent in a dry year, 41 percent in a wet year. These “wild and scenic” rivers are primarily on the remote North Coast where there is little agricultural or urban demand. The Eel River, for example, carries a larger volume of water than either the San Joaquin or American River.
The California Drought website has a link, titled How Water is Used in California, which has chart and narrative information about environmental, agricultural, and urban water use. Water use in the Delta is described in all three categories of uses.