The city of Riverside has filed a lawsuit against the state over water-cutting drought mandates ordered by the governor.

Riverside has its own groundwater supplies from the Bunker Hill Basin and is independent of imported water, said Kevin Milligan, deputy general manager at Riverside Public Utilities.

Acting on Gov. Jerry Brown’s orders, the State Water Resources Control Board is requiring suppliers to cut between 8 and 36 percent from 2013 levels, depending on past use. The goal is to reach an average statewide reduction of 25 percent by next February.

Riverside has been ordered to cut 28 percent.

The city applied to the state to be included in a special tier requiring only a 4 percent reduction, but was denied. The 4 percent tier requires a reliable water supply, but applies only to surface water, not groundwater, he said.

The lawsuit, filed June 4, seeks a temporary restraining order and injunction. The city wants to have groundwater included in the criteria for the 4 percent tier, Milligan said.

“The only difference is surface water you can see and groundwater you can’t,” he said.

The state has not been served with notification of the lawsuit, Milligan said. The city was waiting for the outcome of a yet-to-be-scheduled meeting with the state to see if a resolution could be reached, he said.

State water board officials could not immediately be reached for comment.

To make itself water independent, the city has invested in the John W. North Water Treatment Plan, drilled new wells, captures storm water from the Seven Oaks Dam and has spent $10 million dollars on recycled water infrastructure, he said.

Thought it has been drawn down in the drought, the Bunker Hill Basin has at least 1.4 million acre feet of storage left and maybe as much as 5.4 million acre feet, Milligan said. One acre-foot of water is enough to serve two families for a year.

Contact the writer: jzimmerman@pe.com or 951-368-9586