The Wall Street Journal has an interesting article on the "scapegoating of California farmers":
http://www.wsj.com/articles/californias-farm-water-scapegoat-1428706579
http://www.wsj.com/articles/californias-farm-water-scapegoat-1428706579
A common claim is that agriculture consumes about 80% of “developed” water supply, yet this excludes the half swiped off the top for environmental purposes. Farmers typically consume about 80% of the remainder, so only 40% of the total. Urban users get the rest. Note also that state and federal water projects, which export water from the Delta, have slashed contractual allocations more for agriculture than to urban users. See the nearby chart.