Modesto, irrigation districts, county, other cities form agency to manage groundwater

Stanislaus County leaders on Tuesday approved a groundwater management agency for the Modesto and Oakdale area in a territory that’s been ground zero for debates over pumping and dry residential wells.

The big water players, the Modesto and Oakdale irrigation districts, are joining with Modesto, Riverbank, Oakdale, Waterford and the county in forming a “groundwater sustainability agency” to comply with state law. The new agency has quite a long name: The Stanislaus and Tuolumne Rivers Groundwater Basin Association Groundwater Sustainability Agency.

Those same entities are in a groundwater planning association formed in 1994 that has worked on management of what’s called the Modesto groundwater basin. That basin is a source of water for Modesto’s 212,000 residents, as well as businesses, farmers, residents of the smaller cities and rural homeowners.

An outcry was heard when the county issued hundreds of permits for agricultural wells in the area during the intense drought; the rush on permits finally stopped when the county adopted tougher requirements for applications in November 2014.

Following the state’s groundwater management law of 2014, the cities and irrigation districts decided to join in a groundwater sustainability agency, which must be formed by June 30 to comply with the state. The boundaries are the Stanislaus River on the north, the Tuolumne River on the south, the San Joaquin River on the west and the Sierra foothills on the east.

The groundwater basin is not in what regulators call “critical overdraft” most likely for two reasons: The irrigation districts deliver river water to irrigate farmland, serving to replenish groundwater; and Modesto relieves pressure on its wells by piping treated river water to customers.

That could change with time, however.

Local officials fear that a state plan to double reservoir releases in the spring, to restore salmon and reduce salinity in the Sacramento-San Joaquin Delta, would take surface water away from agriculture, fallowing an estimated 210,000 acres across two counties. That would result in massive groundwater pumping for irrigation, officials fear.

The new GSA has five years to prepare a plan for sustainable management of the Modesto groundwater basin. According to an agreement approved Tuesday, the Stanislaus and Tuolumne agency will evaluate the area’s groundwater supply; promote groundwater planning; and assess the need for improved water extraction, storage, delivery, conservation and efforts to replenish aquifers.

The group will also share information and guidance for “management, preservation, protection and enhancement of groundwater quality and quantity” in the basin.

The cities and irrigation districts each will appoint a staff member to a committee for governing the agency. The GSA will have an annual budget when projects are necessary. Members will be expected to pay their share of costs or lose their vote on the committee.

John Davids, chairman of the groundwater management association, said the state wants to see groundwater planning to prevent “undesirable results” such as saltwater intrusion and subsidence.

Davids, the assistant general manager of water operations for MID, said the Stanislaus and Tuolumne planning association, since its inception in 1994, has completed projects with the U.S. Geological Survey and created a groundwater model.

What’s been most effective in keeping the basin out of trouble, he said, is surface water irrigation and a water treatment plant at Modesto Reservoir, which has supplied 700,000 acre feet of water to Modesto since 1994. Without the treatment plant, that amount would have been pumped from the ground under Modesto. “We have seen water levels rebound below Modesto,” Davids said.

He expects the state-required groundwater plan for the basin will include some recharge efforts. The plan will need to win approval from the state Department of Water Resources.

Other basins

On Tuesday, county supervisors also approved a partnership pieced together for the Eastern San Joaquin Subbasin in what’s known as the “Northern Triangle” of the county, north of the Stanislaus River, and including a piece of Calaveras County. For this groundwater sustainability agency, the county will team with remote partners including the Calaveras County Water District and Rock Creek Water District.

The area dominated by grazing land is critically overdrafted, requiring a groundwater plan by Jan. 31, 2020.

Also approved was the Northwestern Delta-Mendota GSA, for which Stanislaus and Merced counties will develop a groundwater plan. West Side areas tied into the agency include the former Crows Landing Navy airfield and some wildlife refuges. A plan for the overdrafted area is due by January 2020.

In western Stanislaus County, Patterson, Del Puerto Water District, West Stanislaus Irrigation District, the Central California Irrigation District and other entities decided to form their own groundwater agencies under the state law, said Walter Ward, water resources manager for Stanislaus County.

In January, county leaders approved groundwater sustainability agencies for the east and west Turlock subbasins.

This story was originally published February 14, 2017 at 7:37 PM with the headline "Modesto, irrigation districts, county, other cities form agency to manage groundwater."