State water regulators approved landmark groundwater rules Thursday for 850,000 acres of farmland across Fresno, Tulare, Kings and Kern counties.
About 7,200 growers will be regulated in the program, which is part of a larger effort called the Irrigated Lands Regulatory Monitoring Program.
The Central Valley Regional Water Quality Control Board met in Fresno Thursday for a day-long public hearing before voting. The hearing covered details of previous meetings and workshops over the last year.
Each farm must go through an evaluation. Areas with a history of contamination problems will have to do additional monitoring and paperwork. That might include drilling monitoring wells, hiring consultants and testing water.
The San Joaquin Valley's underground water is known for nitrate contamination, which comes from fertilizers, septic systems, sewage treatment and decaying plants. University of California at Davis researchers last year found 96 percent of the problem comes from agriculture.
Farmers have long worried about the cost of the new regulations. State water regulators estimate it will be less than $2 per acre, but farm water leaders figure it's a range from $3 to $10 per acre.