The drought has brought increased scrutiny of water use in California, with focus on who uses how much and for what purposes. This attention is not surprising since scarcity is affecting all water use sectors. Along with this interest, however, comes an array of confusing and often conflicting claims about water use. To help organize the discussions about water use policy, our researchers at the Public Policy Institute of California prepared a brief fact sheet that describes use in three sectors: agricultural, urban, and environmental. In addition, an accompanying blog post explains how environmental water is calculated and why people tend to overstate its impact on urban and agricultural water supplies.
Among the state’s ten hydrologic regions, water use is greatest in the Sacramento Valley, averaging approximately 22.5 million acre-feet (maf) per year in the period 1998-2010. In this region, environmental use constitutes roughly 62 percent of applied water use, agricultural 34 percent, and urban 4 percent. Agricultural use during this period was dominated by rice (39 percent), fruit and nut trees (20 percent), irrigated pasture (17 percent), and alfalfa (10 percent). Approximately 45 percent of environmental water in the Sacramento Valley (or 28 percent of the region’s total water use) was allocated to maintaining water quality and habitat in the Delta. Water for instream flows accounted for 31 percent of environmental water use, Wild and Scenic Rivers 21 percent, and managed wetlands 3 percent.
It is important to note that all of these figures report applied water, meaning water that is allocated for a specific purpose. Yet much of this water, particularly water used to farm rice and for environmental purposes, gets used again, sometimes many times over. As a result, “net” water use is often much lower than applied water use.