Focusing on demonstrating cost effective agricultural BMPs (On-Farm Flood Flow Capture) to retain and infiltrate storm waters, Kings Basin, CA — USDA Conservation Innovation Grant Program
Bachand, P.A.M. , W.R. Horwath , S. Roy , J. Choperena , and D. Cameron. 2011. Final Report: Implications of Using On-Farm Flood Flow Capture To Recharge Groundwater and Mitigate Flood Risks Along the Kings River, CA. For Grant Agreement No. 68-9104-0-128 between Bachand & Associates and the United States Department of Agriculture Natural Resources Conservation Service. September 30, 2012.
Bachand, P.A.M., W.R. Horwath, W.R., S.B. Roy, J. Choperena and Cameron, D. (2011) Fact Sheet: On-Farm Flood Flow Capture – addressing flood risks and groundwater overdraft in the Kings Basin, with potential applications throughout the Central Valley. Davis, CA, Bachand & Associates, 4pp.
The San Joaquin Valley (SJV) faces two large hydrologic issues: severe and chronic groundwater overdraft and flooding risks along major rivers. Capturing sufficient flood flow volumes for groundwater recharge could help address these two pressing issues of groundwater overdraft and flood risks. However, snow pack, precipitation, reservoir volume and flood risks affect reservoir releases, leading to flood flows along the major rivers which vary greatly in their frequency, duration and magnitude. This variance makes dedicated, engineered recharge approaches using public lands expensive. This issue becomes more critical with greater uncertainty for California’s water supply and growing demand.
Within this complex regulatory and hydrologic environment, groundwater recharge opportunities still remain. Promoting stormwater and flood flow capture and recharge on private agricultural lands is an untapped opportunity that could increase groundwater supplies through direct and in lieu groundwater recharge. Additionally, this approach could significantly reduce downstream flood and nonpoint water quality impacts and flood risks.
This project in the Kings River Basin, awarded directly by NRCS to Bachand & Associates, is the first project to test the technical feasibility and logistics of utilizing private farmlands for dual use: agriculture and flood capture and recharge. The study determined on-farm infiltration rates, assessed logistics, and considered water quality as related to potential transport of nitrate and electrical conductivity (EC) to groundwater. For our average infiltration rates of 2.5 in d-1 (6 cm d-1), we estimated 10 acres needed to infiltrate 1 cfs (0.3 cms) of flood flows. Applied Kings River flood flows had nitrate and EC levels one tenth or less than for pumped groundwater. A preliminary cost assessment showed the approach cost effective in comparison to relying on pumped groundwater. In the early years, leaching of legacy salts and nitrates from the vadose zone to the deep.