Comment period on sustainable groundwater plan closes Aug. 25

A map of the Eastern San Joaquin Groundwater Subbasin is pictured. 

The deadline for Calaveras County residents in the northwest part of the county to comment on the Eastern San Joaquin Groundwater Authority’s (ESJGA) Groundwater Sustainability Plan (GSP) is Aug. 25.

For Calaveras County, the plan pertains to about 500 combined residents between Wallace Lake Estates and Valley Springs that rely on groundwater, according to Calaveras County Water District (CCWD) Water Resources Program Manager Peter Martin. Impacts from future activities would mostly be for large water users, like farmers or municipalities, he added.

Passed in 2014 by former Gov. Jerry Brown in the face of one of the most severe droughts in state history, the Sustainable Groundwater Management Act (SGMA) kicked off a five-year process to provide a framework for improved groundwater management by local agencies across the state through 2040. Boundaries were divided by groundwater subbasins across the state, and several “groundwater sustainability agencies” (cities, counties and water and irrigation districts, mostly) within those subbasins were tasked with producing their own plans to be submitted in one overall plan.

The 70-square-mile Eastern San Joaquin Groundwater Subbasin is bounded by the Sierra Nevada foothills to the east, San Joaquin River to the west, Dry Creek to the north, and the Stanislaus River to the south. It’s one of 21 basins and subbasins identified by the California Department of Water Resources (DWR) as being in a state of critical overdraft. Over-drafting means that more water is pumped from a groundwater basin than is replaced through sources like rainfall, irrigation water, streams fed by mountain runoff and intentional recharge efforts (spreading surface water to feed into the basin).

Current analysis indicates that the entire basin is over-drafted by 78,000 acre-feet (the volume of 1 acre of surface area to a depth of 1 foot) annually, according to the plan. After the framework is laid out, various projects and management actions will help the basin reach a balance between inputs (rivers, rainfall, etc.) and outputs (pumping for irrigation, drinking water, etc.). Those might include groundwater recharge efforts or pumping restrictions on local water districts that are reliant on groundwater, for instance.

The northwest portion of Calaveras County falls within the East Side San Joaquin GSA, a partnership among Calaveras County, CCWD, Rock Creek Water District and Stanislaus County. From the south end, this section of the basin sits beneath the Salt Springs Valley to New Hogan Reservoir, through Valley Springs and up to the Mokelumne River.

In the next six months, those partners – along with 15 other GSAs – have to work together to finalize a long-term framework for managing groundwater use across the entire subbasin, including portions of Stanislaus and San Joaquin counties. That’s due to the state by Jan. 31, 2020. The 16 agencies have been developing the plan since late 2017.

The state designated six undesirable impacts related to groundwater use to mitigate, including chronic lowering of groundwater levels, reduction in groundwater storage, seawater intrusion, degraded water quality, land subsidence and depletion of interconnected surface water.

Chronic lowering of groundwater levels is the most concerning for not only Calaveras County, but the entire basin, according to Joel Metzger, CCWD’s manager of external affairs.

“Based on the Draft Plan, this will be the linchpin for measuring the success of meeting objectives long-term,” he said in a July 24 email.

The “interconnected surface water” impact is also of concern in Calaveras County, Martin said. That refers to the interactions between surface water (streams, rivers and lakes) and aquifers, or underground bodies of rock that store large volumes of groundwater. If the water table adjacent to a river or stream decreases in elevation as a result of groundwater pumping, the river or stream may lose water to the underlying aquifer, thereby impacting fisheries, water quality and water rights of users downstream.

Beyond the state-designated impacts, Martin said the largest challenge that remains is a lack of reliable data on groundwater use, especially in Calaveras County.

Projections of future groundwater storage are based on hydrological models that attempt to quantify the subbasin’s intake of water versus how much is pumped out, but these have limitations, Martin said.

“It’s too complex of a system to really know,” Martin said. “That’s part of the reason why monitoring is important, so you don’t end up spending millions on projects that may not be necessary.”

Martin said the first five years of the plan will be gaining a better understanding of the basin through investing in monitoring wells, since Calaveras County doesn’t have a long record of measured groundwater data. Whereas many areas in the San Joaquin Valley have 40 to 60 years of data, many of the monitoring wells in Calaveras County were installed in the past decade under CCWD’s Groundwater Monitoring Program.

A landmark bill, SGMA was crafted with the intent of shifting traditional views of groundwater use from the current siloed approach to one that’s more collaborative and regional in scope, according to Walt Ward, water resources manager for Stanislaus County and a retired hydrologist.

“It breaks down these institutional walls so that cities, counties and irrigation districts are all working together with common goals and purposes while retaining their local control,” he said at a meeting in Stockton. “Not stepping on anybody’s water rights, or interfering with anybody’s local operations, but trying to change the mindset and the view toward a more regional collaborative process.”

The plan will have to take into account land-use projections and development goals of local governments as they may apply to groundwater use, Ward said.

For example, a big issue in eastern Stanislaus County is a rising water demand due to an influx of almond and walnut growers, according to Ward. Landowners will have to work with their local irrigation districts to balance groundwater use with water use from other sources, such as reservoirs, potentially. That could require developing the proper infrastructure to move water from upstream reservoirs, or looking to other sources, such as stormwater to recharge aquifers.

“We’re just trying to get to the go line; it’s the implementation over the decades ahead of us that matters,” Ward said of the plan. “The point is everyone can’t be completely reliant on groundwater. So we’re trying to shift to conjunctive use,” using groundwater and other water sources together.

These are the kinds of issues that the GSP will have to address.

“We want the public to make sure they feel there’s something meaningful is being done to protect their water sources,” Martin said. “We encourage them to review the plan and become informed.”

Visit to view the Eastern San Joaquin Groundwater Authority’s Groundwater Sustainability Plan. Comments must be emailed to by Aug. 25.



Davis graduated from UC Santa Cruz with a degree in Environmental Studies. He covers environmental issues, agriculture, fire and local government. Davis spends his free time playing guitar and hiking with his dog, Penny.

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