So...none of the 40-60 inches of precip across the Sierra Nevadas ever runs down into the valley.? We're not in Kansas anymore. Significant amounts of water flow into the land rather than falling from the sky. To insist they farm as if the 5" that falls is all they get is probably why you always sucked at SimCity.
They need new reservoirs and they need to expand others to hold more during wet years. Im surprised the who,e valley isn't covered in greenhouses with hydroponics like Spain. But then...Spains produce is terrible and flavorless.
I support having new reservoirs but not growing crops that require intensive irrigation year round. Of course, watering lawns doesn't make much sense either....