California lawmakers are looking at ending the state's status as one of the last in the West to start managing groundwater.
State law, dating from the Gold Rush era, lets individual landowners pump up as much water as they choose.
But in this year of drought, underground water is supplying up to 65 percent of California's water.
The state says water users are now using far more groundwater - enough to supply 2 million California homes for a year - than snow and rain are putting back each year.
A bill headed to the state Assembly by the end of the month would introduce California's first comprehensive groundwater management plan, putting the pump-as-you-please policy to the test