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Yolo-Zamora Groundwater Recharge Pilot Project

The YSGA received $1.2 million from DWR's SGMA Implementation Grant to implement the Yolo-Zamora Groundwater Recharge Pilot Project. This project is a partnership to divert up to 2,000 acre-feet of excess Cache Creek storm flows per year from the Capay Dam, conveyed through the West Adams Canal system to China Slough and on-farm groundwater recharge sites. The YSGA and the Yolo County Flood Control and Water Conservation District (YCFC&WCD) are partnering with local landowners in the Yolo-Zamora area of Yolo County to improve China Slough and convey excess storm flows through the Slough to enhance groundwater recharge and sustain groundwater levels. This comprehensive project includes a pilot project, feasibility study, design and engineering, canal system improvements, and permitting. The multiple benefits of this component include increasing groundwater recharge, alleviating land subsidence, alleviating groundwater level declines, increasing groundwater storage, capturing canal system losses, and reducing potential flood risk.

The project will consist of the following four broad objectives: 

1) Complete the study and other work necessary to identify any available surface water supplies that the Partners can divert to the Yolo-Zamora area

2) Improve the District’s canal system to remotely control and manage the conveyance of excess storm flows

To responsibly prepare for conveying and monitoring excess storm flows, the District is upgrading the East Adams and Acacia Canals, which are part of the West Adams Canal mainstem,  to increase the capacity of the canal; optimize conjunctive use management by re-using drain water and conserving spill or losses out of the canal system; and to facilitate groundwater recharge opportunities in the Yolo Subbasin. Canal upgrades include:

  1. adding three new culverts (and enlarging existing culverts)
  2. installing three new check structures
  3. installing five new automatic gates allowing for automated control of the canal.

The structures to be upgraded are depicted on the project map at the bottom of this page. The District expects the upgraded East Adams and Acacia Canals will deliver a maximum of 40 cfs (an increase from the current 25 cfs) and will allow automated control of diversion and conveyance of excess storm flows from Cache Creek for groundwater recharge in the Yolo-Zamora area of Yolo County via China Slough. Ultimately, excess storm flows of up to 7,200 acre-feet could be conveyed for recharge in the future.

3) Evaluate the feasibility of rehabilitating the slough to deliver water to the Yolo-Zamora area

China Slough is a naturally ephemeral storm drain channel that landowners and Yolo County have historically modified to serve as an irrigation drainage system. Currently, parts of the channel are blocked by debris and overgrown vegetation; reconnaissance and rehabilitation of the Slough will be necessary to prevent pollution and facilitate groundwater recharge. According to UC Davis’s Soil Agricultural Groundwater Banking Index, groundwater recharge potential around China Slough is generally “excellent” or “good.” This project will evaluate overall technical feasibility, propose changes to China Slough for future modifications, and complete a cost-benefit analysis and an environmental review for rehabilitating China Slough.

4) Implement pilot projects to demonstrate groundwater recharge potential in the Yolo-Zamora area.

One component of this project is to implement a “trickle flow” pilot project to determine the feasibility of supporting a future expanded groundwater recharge project that could significantly increase groundwater levels and benefit domestic drinking water wells in the Yolo-Zamora area. The “trickle flow” concept is the idea of sending water at low flow rates through ephemeral streams to maximize infiltration rates and provide groundwater recharge. The pilot project will send a trickle flow (~10 to 20 cfs) into China Slough via the upgraded Acacia Canal spill site. Diverted water will travel 16 miles through an earthen, unlined canal from Capay Dam to the Acacia Canal spill site in an area with demonstrated successful groundwater recharge. (During the irrigation season, approximately 25% of all water transported through the irrigation canal system is recharged to the groundwater aquifer.)

There are also funds to implement a pilot project to operate and manage recharge projects on farmers’ fields; the Partners will work with willing landowners to implement recharge projects through on-farm flooding, 23 of whom signed letters of support for this project. The pilot project will ensure the feasibility of and demonstrate the benefits of groundwater recharge through China Slough and onto adjacent farmer fields by measuring “trickle flow” diversions into the heading of China Slough, tracking the conveyance of water and re-diversions onto farm fields, and measuring changes in groundwater levels using the Partners’ existing system of groundwater monitoring wells. The Component is estimated to provide a short-term benefit of recharging up to 2,000 acre-feet per year during the grant period, with larger benefits up to 7,200 AF/year in the long term if the pilot project is expanded.

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