More like you get rid of the subsidies so that water costs $20/barrel and suddenly people won't waste so much of it, and the well will never run dry.
The price would never go that high. I live in San Jose, California, and as a retail customer I pay about $1/HCF (hundred cubic feet) of potable water. A HCF is 748 gallons. So one gallon costs me $0.0013. A standard barrel is 42 gallons. So clean, drinkable, chlorinated, fluoridated water currently costs about 6 cents per barrel. Farmers receive non-potable water, that is heavily subsidized, so they pay far less than that. So even if the price of a barrel of water went up, for everyone, to a dime, our water problems would be over.