Groundwater Recharge: a New Threat to California Streams

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The Scott River is now dewatered even in years of “average” precipitation as a result of unregulated groundwater extraction for irrigation. Photo courtesy of Felice Pace.
The Scott River is now dewatered even in years of “average” precipitation as a result of unregulated groundwater extraction for irrigation. Photo courtesy of Felice Pace.

A new threat to stream ecosystems has emerged in groundwater planning. “Replenishment,” as described in a white paper by the Department of Water Resources (DWR), claims that declining groundwater levels and related land subsidence can be reversed by diverting high winter and springtime streamflow to groundwater storage. The State Water Resources Board has already funded projects to divert high flows to replenish groundwater, including in the Scott River Basin, a major Klamath River tributary.
This plan may seem to make sense, but as clearly demonstrated in streams where high flows are blocked by dams, streams are not healthy when they are denied naturally high seasonal and storm flows. Only scientifically robust flow assessments can determinate how much water must remain in a stream during each month or season of the year to protect the ecosystem and fisheries. That amount of streamflow will also vary depending on whether the water year is dry or wet.

Assessing Year-Round Streamflow Needs

The California Legislature mandates that the California Department of Fish & Wildlife (CDFW) prepare flow assessments for California streams and transmit those assessments to the State Water Board for use in evaluating new proposals for streamflow diversions. However, flow assessments have been completed for only a handful of streams.
Water conservation, recycled water, desalinated water, and transfers of water from one jurisdiction to another are also potential sources for groundwater recharge, but high storm and seasonal flows represent the largest potential source of “new” water for groundwater replenishment and is most likely to be targeted.

Unfortunately, the Replenishment white paper does not even mentioned DFW’s flow assessments or clearly state that year-round flow needs must be determined prior to appropriating flows for groundwater storage. Furthermore, DWR admits in the paper that its estimates “…may not fully capture competing needs associated with instream flows to support habitat, species (including endangered or threatened species), water quality, and recreation.”

Because streamflow needs are ignored, DWR’s estimates of the amounts of water available for diversion to groundwater storage in each region is clearly a gross overestimation, which is of great concern. The graph below highlights that concern by comparing DFW’s estimates to those made independently by UC Davis scientists.

Graph comparing CA Department of Fish and Wildlife estimates to those made independently by UC Davis scientists.
Graph comparing CA Department of Fish and Wildlife estimates to those made independently by UC Davis scientists.

By ignoring instream flow assessments and creating unrealistically high estimates of surface water available, DWR has created the expectation that declining groundwater can be reversed by appropriating seasonally high springtime and storm streamflow. As a result, we can expect a flood of new water rights applications that ignore or inadequately assess stream needs. Advocates for healthy streams should participate in groundwater management plans currently being developed for Eel River and Smith River estuary lands as well as for the Scott and Shasta Valleys. Only the direct involvement of stream advocates will assure that year-round flows, including high storm and springtime flows needed to maintain healthy stream ecosystems, are properly assessed and protected.

[Links to documents and more information will be added to this article soon.]

Events

One need not be a Sierra Club member to participate in these outings. Please join us!

Sunday, September 16: North Group Prairie Creek State Park Friendship Ridge Hike. Loop includes old-growth forest, waterfalls, and likely elk. Some steep, rough, or soggy places. Bring food, water, and hiking footwear. No dogs. Class Medium difficulty, 8 miles, less than 1000 feet elevation change. Carpools 9 a.m. Valley West (Ray’s) Shopping Center, 10:30 a.m. Fern Canyon trailhead (exit Hwy. 101 at Davison Rd.). Leader Ned 707-825-3652, [email protected] Bad weather cancels.