Here in southern Ohio, cisterns are probably more common than wells. The cisterns are supplied either by rainwater from home gutters or commercial water haulers who bring in water. My house here has two large cisterns although we now are supplied by a private county water system.
As for saying that the state has no right to tax people's private wells, remember, those wells are tapped into underground aquafers that are often very large so someone pumping high volumes is taking water from under neighbor's land. Two acre feet is a lot of water, 28,000 gallons pr month. We only use 2500-5000 gallons a month with most of the variation going to watering our seven horses, So anyone using more than 2 a/f of water is probably a commercial operation, likely taking water from beyond their own land.
As I understand it, southern California has a major water resource problem so trying to limit excess use sounds reasonable to me, something rare for California politics ;-)
Ken