Agriculture is the big culprit, taking 80% of the state's water
Nonsense. In the first place, half the state's ground water flows to the sea and is never tapped for various reasons (e.g., recreational and environmental). Agriculture does take 80% of what's left, which means it only uses 40% of the state's water. You have to treat the recreational and environmental uses of water as part of the overall issue. They reflect choices by the state's population, just as having a green lawn does. The environment won't collapse if the delta smelt gets trapped in irrigation pumps, preserving it instead is a choice made by others.
While this has been the worst drought on record, in the past agriculture and the state's urban areas have always managed to get by during previous droughts. What's seldom mentioned, for example, is that California's population has grown since the last major drought, and there have been more mandated environmental diversions. But of course, nobody ever considers these as part of the problem.
If you want food, it takes plenty of land, plenty of sunshine, and plenty of water. It happens that California has some of the best land and sunshine in the world for growing crops. Water was always an issue. But to say that agriculture "wastes" water is nonsense. Even when it's subsidized, it's still a major cost to any Californian farmer. There have always been incentives to reduce its use. I grew up on a California farm from the '60s to the '80s, and saw the advent of drip irrigation, sophisticated monitoring, and other advances. The state even metered the wells in our area in the '80s and eventually started charging for water.
It's easy for people who have never been on a farm to point fingers. But how many of them run the faucets while they shave or brush their teeth, never turn off the shower while they soap up, and over-water their lawns? This is just the tyranny of the majority over a minority -- one which provides a product essential to life.