New study, old data in Stanislaus County effort to manage groundwater

A long-awaited tool created to help manage groundwater was unveiled Wednesday to the Stanislaus County Water Advisory Committee, whose members listened politely but seemed less than thrilled.

The 10-year, $1.25 million effort by the U.S. Geological Survey, aimed at understanding and predicting how water moves underground in this region, relies on data at least 11 years old. That was before growers began pumping groundwater in earnest to feed millions of new almond trees blanketing the county’s east side, and before the ongoing four-year drought.

“It’s just another tool to use, along with the data we’re gathering (now),” said County Supervisor Terry Withrow.

Some maps displayed by USGS hydrologist Steve Phillips reflected common knowledge, such as one showing a so-called cone of depression east of Turlock where severe overdraft was threatening groundwater levels even in 2004. Eastside Water District growers receive no surface water from rivers or canals and depend entirely on wells in that area.

Another map suggested good soils for groundwater recharge, or replenishing aquifers, such as south of Oakdale.

Phillips said his presentation soon will be available to the public.

The study was funded by the county; the USGS; the Modesto and Oakdale irrigation districts; and the cities of Modesto, Riverbank and Oakdale. The Turlock Irrigation District contributed groundwater data to the project.

Phillips called the model “a good platform” upon which to build using more recent data to be gathered from cities, irrigation districts and state water agencies. A consultant has been hired to wring numbers from private well owners, especially in vulnerable areas on the county’s east side.

“These are all threads we’re trying to weave together,” said Walter Ward, Stanislaus’ water resources manager.

Withrow said the prolonged drought may help people realize the importance of sharing useful information. “It seems like resistance is going away,” he said.

The Water Advisory Committee, composed of officeholders and volunteers – many with stakes in agriculture, water and drilling – also voted Wednesday to pursue creating an agency to oversee groundwater management using an “integrated subbasin approach.” That means coordinating with leaders from San Joaquin and Merced counties, because the groundwater basin under much of Stanislaus extends beyond county lines to the north and south.

Another committee soon will propose a structure for an “overarching coordinating committee,” with members from Stanislaus agencies and perhaps the South San Joaquin and Merced irrigation districts. The proposal eventually would go to a vote of Stanislaus supervisors and perhaps leaders in the neighboring counties.

Bee staff writer Garth Stapley can be reached at gstapley@modbee.com or (209) 578-2390.