Talk to the environmentalists and other Leftists. They are the ones who have either refused to address water management over the last century or impeded efforts to do so.
Eventually, “climate change” will be blamed.
It is not necessary, in California, to pump groundwater for irrigation. There is sufficient snowpack on the western side of the Sierra Mountains east of the Napa Valley to more than supply sufficient water for a full and sustainable annual crop of grapes.
For years, California had an excellent and well-managed water distribution system all up and down the Central Valley, and the agricultural interests prospered mightily. The San Joaquin and Sacramento valleys were the bread basket for much of the United States and enjoyed an excellent export market. But somebody, or several somebodies, determined that using water for agricultural purposes was “wasteful” and resulted in an extraordinary amount of “pollution”, so all the retention dams were blown up, and the sloughs were diverted to the San Francisco Bay to restore the habitat of some otherwise relatively insignificant species of fish.