Cup half full

Groundwater tells different story than reservoirs, rivers

The wet winter and spring may have given the appearance of a water bounty in the North State, but conditions above ground do not necessarily indicate volume in aquifers.

The wet winter and spring may have given the appearance of a water bounty in the North State, but conditions above ground do not necessarily indicate volume in aquifers.

Photo by Evan Tuchinsky

Learn more:
Visit (search “Groundwater”) for details about SGMA, the county’s Groundwater Sustainability Plan and the Groundwater Pumpers Advisory Committee.

The drought has ended.

Californians got that news from no less an authority figure than Gov. Jerry Brown when he lifted the state of emergency he declared three years ago when reservoirs dipped low and snowpacks grew scarce. Brown started rolling back water restrictions early this year and, stating in April that “this drought emergency is over,” formally acknowledged the record rainfall that North State residents observed since winter.

Lake Oroville and Shasta Lake have filled—at times near to overflowing. Runoff from snow melt from the Sierra Nevadas promises to keep rivers and creeks flowing at healthy levels at least through the early part of summer.

So, along with the drought, our water worries have ended?

Not so fast—Brown ended his pronouncement with a caveat: “…but the next drought could be around the corner. Conservation must remain a way of life.”

Plus, there’s a piece of the water picture that isn’t as conspicuous as dams or peaks, nor as lush as what’s been painted.

Rivers and reservoirs constitute surface water; underneath the earth, through basins and aquifers, moves groundwater. It’s hard to measure, work to locate, interrelated with but separated from water above ground.

Christina Buck from Butte County’s Department of Water Resources and Conservation told the CN&R that people should not assume supplies have returned to normal just because they’ve seen more surface water.

“Groundwater, and other related effects on ecosystems, have longer memories from drought,” said Buck, a water resource scientist. “Groundwater levels have come up this year significantly compared to what we’ve seen in previous years—especially in Butte County, on the east side where we get more rain—but it doesn’t make up for the cumulative effects of multiple dry years.”

Buck referenced not just the preceding four-year stretch but also the 2007-09 drought as periods when pumping without comparable replenishment diminished aquifer stores.

“We had a nice bump,” she continued, referring to this year’s recharge, “but it’s not a full recovery [to] where we need to be.”

Buck presented spring levels at the May 15 meeting of the Groundwater Pumpers Advisory Committee, or GPAC—a county panel formed by the Board of Supervisors for well-users in “the white areas,” not served by water districts. California’s Sustainable Groundwater Management Act, SGMA, places control of underground basins in the hands of local governments and water agencies; the GPAC accords representation in the rules-setting procedure to rural landowners and environmental groups. (See “Asking for influence,” Newslines, Sept. 15.)

Buck told the seven of nine GPAC members present, plus a dozen other attendees, that statewide surface water conditions went well above average—snowfall 160 percent, precipitation 170 percent, runoff 240 percent—and rainfall in the North Sierra hit a record 93.1 inches. Meanwhile, Butte County groundwater levels—measured via 116 wells—rose an average of 4.8 feet, compared with 1.5 feet the previous year following a drop of 4 feet the year before.

Interestingly, groundwater rose to a greater extent farther away from the Sacramento River, the region’s largest conduit of surface water. Perhaps the cause is geological (the distinct characteristics of underground formations, east versus west); perhaps it’s usage (where more pumpers draw). In any case, this underscores the complex intermix of the two water sources.

Groundwater replenishes through “in-lieu recharge”—using more surface water than groundwater in wet years, thereby reducing the drain on aquifers—and directly by precipitation percolating through soil layers. Buck said SGMA could impact the latter process, “but that has logistical needs, infrastructure needs and legal needs.” Water rights originally got drafted for surface water. Enter groundwater, which not only is trickier to quantify but also flows in cavities that rarely coincide with overland jurisdictions.

SGMA divides authority by underground storage zone, or subbasin. Butte County overlaps four subbasins, so the water department has been working on four governance plans in conjunction with two dozen total agencies. The city of Chico is one such Groundwater Sustainability Agency.

The state set a deadline of June 30 to make sure all the subbasins are covered. Paul Gosselin, Butte County’s water director, said that’s already been met. What looms is a 2022 deadline for completing each Groundwater Sustainability Plan.

“There’s a whole large number of issues we’ve got to sort through,” Gosselin said.

The GPAC will play its part. Said Les Heringer, the committee chair: “We’re the ones who are going to be impacted by whatever plan the county comes up with, so that’s why it’s really important that we’re at the table.”

Eight members, including Heringer from M&T Ranch, are groundwater users—two from each of the subbasins. The ninth, Susan Strachan, represents environmental interests countywide. She’s a former county water commissioner and board member of the Big Chico Creek Watershed Alliance.

Strachan does not feel eclipsed: “A number of them, maybe all of them, are also concerned about overall groundwater conditions and maintaining those, so I don’t know that I see myself as in opposition to anyone on the committee. I think we’re all working for the same thing … there may be differences of opinion about how you get there, but we all have the same goal.”