"California ranks as the leading agricultural state in the United States in terms of farm-level sales. In 2012, California's farm-level sales totaled nearly $45 billion and accounted for 11% of total U.S. agricultural sales. Five counties--Tulare, Kern, Fresno, Monterey, and Merced--rank among the leading agricultural counties in the nation. Given current drought conditions in California, however, there has been much attention on the use of water to grow agricultural crops in the state. Depending on the data source, irrigated agriculture accounts for roughly 40% to 80% of total water supplies. Such discrepancies are largely based on different survey methods and assumptions, including the baseline amount of water estimated for use (e.g., what constitutes 'available' supplies). Two primary data sources are the U.S. Geological Survey (USGS) and the California Department of Water Resources (DWR). USGS estimates water use for agricultural irrigation in California at 25.8 million acre-feet (MAF), accounting for 61% of USGS's estimates of total withdrawals. DWR estimates water use withdrawals for agricultural irrigation at 33 MAF, or about 41% of total use. Both of these estimates are based on available data for 2010. These estimates differ from other widely cited estimates indicating that agricultural use accounts for 80% of California's available water supplies, as reported in media and news reports. […] Congressional interest in California agriculture and water use centers largely on the Bureau of Reclamation's Central Valley Project (CVP), which supplies water to numerous agricultural and municipal contractors. In recent years, the CVP has cut back water deliveries due to drought and environmental factors. Congress also authorizes and oversees U.S. Department of Agriculture support for individual crops and farmers, and some Members have expressed concern over the broader implications of decreased agricultural production and/or lack of water availability throughout the state."
CRS Report for Congress, R44093
National Agricultural Law Center: http://nationalaglawcenter.org/