Groundwater in the Manteca, Ripon and Lathrop areas is projected to drop 10 feet this year when the traditional irrigation season ends on Sept. 30.
But as South San Joaquin Irrigation District General Manager Jeff Shields points out, that is not nearly as steep of a drop as much of the rest of the county were the expectation is to see aquifer levels plunge 15 feet.
While the impacts of three years of severe drought can be seen in rivers, lakes and reservoirs the effect on underground sources are invisible. The situation is exacerbated by the fact dwindling surface water supplies has significantly ramped up pumping and the drilling of new walls.
After past droughts, many times the underground water table didn’t replenish itself.
“After the 1976-77 drought, the water table in the Manteca-Ripon dropped 20 feet,” Shields noted. “Only 10 feet of that was replenished.”
The 2014 Eastern San Joaquin County Integrated Regional Water Management Plan Update noted that the groundwater basin is in recovery mode although increases in pumping due ti the drought poses challenges.
Back in 1980, the Department of Water Resources characterized the Eastern San Joaquin County Groundwater Basin as “critically overdrafted.” That meant if practices in place at the time continued, there would end being a significant adverse overdraft-related impacts. The includes everything from wells running dry to and subsidence.
San Joaquin County water tables have been steadily dropping since the 1920s with periods record of increases before dropping further.
San Joaquin County Farm Bureau water expert Julianne Phillips notes county entities have spent more than $700 million in the past 15 years in an effort to better manage groundwater to slow down depletion rates and start reversing them. The biggest project was the $200 million Stockton surface water treatment plant that allowed the city to use water in the Delta and cease all underground water use. Urban centers are major users of underground water.
The groundwater management bills before the governor that would require mandatory registration of all wells, could impose caps on what each well can pump plus could lead to a ban against new wells even in cities within specific basins has been criticized by Phillips and her colleagues.
“There is a need for groundwater management, we agree to that,” Shields said. “But this (the three last-minute pieces of legislation) isn’t the answer.”
There are areas in the San Joaquin Valley when - particularly south of Merced - where land has sunk significantly since the 1920s imperiling infrastructure as aquifers collapse.
In the last several years land around Firebaugh has dropped an additional two to five feet.
The Delta-Mendota Canal in places has dropped seven feet to effectively reducing the volume of water the canal can move. The California Aqueduct is also being impacted by land subsidence which is one of the main reasons the three groundwater management bills were universally embraced by Southern California lawmakers.
San Joaquin Valley legislators all opposed the measures regardless of party line.
Phillips argued that the one-size-fits-all approach the state is using for California’s 500 plus water basins is bad policy as it fails to take into account groundwater management strides that counties like San Joaquin have done on their own without state help.
Phillips noted the state has actually hindered efforts to recharge the Eastern San Joaquin County aquifer by delaying approval of a project to do just that more than 18 months after it was ready to go to construction.