Aquifer recharge: a way to support streamflow
Data shows Scott Valley’s aquifer is stable. But in light of this prolonged drought, we believe aquifer recharge is a preemptive action that will help all water uses and users.
What is Recharge?
During time of excess flow, surface water from the river is diverted into a ditch, then released at different locations and allowed to spread over dormant farm fields. Since plants don’t take up water when they are dormant, this water percolates into the soil profile and adds to the groundwater storage in the aquifer. This activity is also referred to as Managed Aquifer Recharge (MAR).
How would recharge help?
The water stored underground in this way will increase the amount of groundwater water available to make its way back into the Scott River. With proper management, this extra water will enhance summer and fall flows for the beneficial use of instream fish and wildlife preservation and enhancement. This action is a top priority of the Scott Valley Groundwater Sustainability Plan, recently adopted by Siskiyou County and pending approval by the State. Note that the Scott Valley aquifer is not considered to be in an “overdraft” condition, as its well levels return to normal during average water years.
Unlike surface water storage, groundwater storage does not lose water to evaporation and does not heat up in the summer. If delivery infrastructure for recharge is in place, then the cost for doing this can be very low. In Scott Valley’s case, existing ditches would keep the cost relatively low.
When would recharge happen?
Ground water recharge would be initiated when river flows exceed other needs in the river system, typically during the winter months. In “wet” water years, the aquifer would likely become fully recharged naturally and no additional recharge would be needed. After and during drought years, the aquifer would be replenished more quickly with this artificial recharge.
Where would it happen?
Currently, the drier eastside of Scott Valley has two large ditch systems. With this infrastructure already in place to divert and deliver water, most fields east of the Scott River from about river mile 52 (below Callahan) to about river mile 34 (above Fort Jones) could potentially be used for recharge. If needed, intentional recharge could also occur in other areas of the valley.
What has been done so far?
A pilot project occurred in 2016 that applied 1,355 acre-feet of water on a small alfalfa field below the Scott Valley Irrigation District (Dahlke et al. 2018). The 2016 pilot project was the recipient of the first temporary groundwater storage permit ever issued by the State Water Board, and the project was complimented for “creative thinking and community effort” (SWRCB 2016). Permit approval was accelerated to a few days due to an executive order by then-Governor Jerry Brown.
Another, large-scale project is underway, and is expected to apply up to 5,400 acre-feet in the next few years (SWRCB 2022), though much more could potentially be recharged.
What is needed to help get more recharge?
An easier permitting process for multi-year projects, including an exemption from the California Environmental Quality Act (CEQA).
References
Dahlke, H., Brown, A., Orloff, S., Putnam, D, and T. O’Geen. 2018. Managed winter flooding of alfalfa recharges groundwater with minimal crop damage. Calif Agr. 72(1):65-75.
Borunda, A. (2022). The deceptively simple plan to replenish California’s groundwater. National Geographic. Published online March 23, 2022.
SWRCB. 2016. State Water Board Issues its First Temporary Groundwater Storage Permit to Capture Rain Season High Flows. Press Release of Jan. 5, 2016. Sacramento.
State Water Resources Control Board. 2022. Temporary Permit 21431 (application T033263) to appropriate water from Scott River in Siskiyou County. March 3, 2022. Sacramento. 32 p.
Siskiyou County Flood Control & Water Conservation District. 2021. Scott Valley Groundwater Sustainability Plan. Ch. 4 – Projects and Management Actions. Yreka, CA.