(numbers not precise at all)<p>I see that graph of rainfall, jumping between ~350mm in droughts and ~700mm in wet years; From what I hear, the farming industry has allocated perhaps 3000mm of water rights, is presently consuming maybe 600mm (depleting aquifers) down from their usual 700-800mm, and is complaining about reservoirs running dry and water deliveries not showing up. Water rights that the owner does not attempt to use in a given year are lost forever: It's not "Finder-Keeper", it's even worse than that, overconsumption is being guaranteed by this system.<p>If California wants to be sustainable - and not that word has a specific meaning, 'to be able to continue indefinitely', rather than a vague greenness - it needs to reduce the number it actually uses to perhaps 200mm-300mm. Because reservoirs have run low, aquifers have been mined dry, saltwater intrusion and subsidence has been happening, and the geomorphology has been all out of whack. The invisible damage they're doing to the natural resources they rely on using just 100% of rainfall is enormous; They've killed most of the native ecosystem, most of the native rivers entirely, and turned the hills to fire tinder; The un-farmed areas rapidly went from grassland and swamp to desert. At 175% of rainfall things begin to happen like destroying the topography ("Congratulations, your farm is now on a hill. Water doesn't flow uphill.") which have overt, direct externalities, things visited on one's neighbor rather than on one's great-grandchildren. That's insane. One wouldn't expect even a rugged individualist frontiersman to tolerate their neighbor jacking up their property a few millimeters a day in the dead of night in order to rob them of canal usage; Shotguns would be employed in remedy. Aquifers have an interesting property in that they're not necessarily trivially refillable - pore spaces compress and become less permeable. If you let the Everglades loose again, eliminating humans from Florida, it would look drastically different than it looked in pre-Columbian times because the land has sunk and water would now flow over it rather than through it.<p>So: What will cut back agricultural water usage (<i>usage</i>, not deliveries from canals) by around 2/3 in a durable way, which minimizes the hit to GDP? That's what California should be asking itself. Anything which accomplishes this goal is acceptable from a sustainability & environmental standpoint, be it bureaucratic micromanagement, pricing, blanket moratoriums, state seizure, <i>whatever</i>.