Implications of Using On-Farm Flood Flow Capture To Recharge Groundwater and Mitigate Flood Risks Along the Kings River, CA

Abstract

The agriculturally productive San Joaquin Valley faces two severe hydrologic issues: persistent groundwater overdraft and flooding risks. Capturing flood flows for groundwater recharge could help address both of these issues, yet flood flow frequency, duration, and magnitude vary greatly as upstream reservoir releases are affected by snowpack, precipitation type, reservoir volume, and flood risks. This variability makes dedicated, engineered recharge approaches expensive. Our work evaluates leveraging private farmlands in the Kings River Basin to capture flood flows for direct and in lieu recharge, calculates on-farm infiltration rates, assesses logistics, and considers potential water quality issues. The Natural Resources Conservation Service (NRCS) soil series suggested that a cementing layer would hinder recharge. The standard practice of deep ripping fractured the layer, resulting in infiltration rates averaging 2.5 in d(-1) (6 cm d(-1)) throughout the farm. Based on these rates 10 acres are needed to infiltrate 1 cfs (100 m(3) h(-1)) of flood flows. Our conceptual model predicts that salinity and nitrate pulses flush initially to the groundwater but that groundwater quality improves in the long term due to pristine flood flows low in salts or nitrate. Flood flow capture, when integrated with irrigation, is more cost-effective than groundwater pumping.

Impacts of the 2013 Extreme Flood in Northeast China on Regional Groundwater Depth and Quality

“…Therefore, a large amount of nitrogen and chloride could have leached into the shallow groundwater with the flood waters. In their studies on surface and aquifer water quality in the Sanjiang Plain, Cao et al [17] and Bachand et al [31] found that Cl − and NO3 − concentrations and EC all increased during floods on farmland due to the infiltration of surface application of fertilizers and pesticides. Cao et al's study [17] showed several wells in the region with suspiciously high NO3 − concentrations (up to 153.29 mg/L).…”

Unanswered questions for implementation of the Sustainable Groundwater Management Act

“…In the same way that Apple assembled existing microprocessor, battery and display technologies and developed the iPhone, a number of researchers, including Helen Dahlke (UC Davis), Phil Bachand (Bachand & Associates) and others, are combining underutilized resources -winter flood flows, water conveyance infrastructure and offseason farmland -together to create something new (Bachand et al 2013;Bachand et al 2016;Harter and Dahlke 2014;O'Geen et al 2015).…”

Economic Feasibility of Irrigated Agricultural Land Use Buffers to Reduce Groundwater Nitrate in Rural Drinking Water Sources

“…In addition, recent work by Bachand et al [67] also demonstrates the potential of alfalfa fields and vineyards to be used for additional groundwater recharge, e.g., using flood waters. Alfalfa and vineyards were selected for the analysis here also because they are in high demand, are suited to the local climate, and require little or no nitrogen fertilizer; as a leguminous N-fixer, alfalfa can be expected to produce relatively low amounts of N leaching, while allowing for significant groundwater recharge through intentional over-irrigation.…”

“…Recharge basin installation and operating costs is on the order of $20,000/hectare annualized [85]. However, supplemental surface water used for recharge in the buffers may help prevent or alleviate flood damage; flood damage from the Kings and San Joaquin Rivers is estimated at $740 million since 1983 [67,86]. Benefits from avoided damage costs elsewhere are yet to be estimated; however, the calculations used here account for flood damage avoidance costs.…”

“…This may include redesigning irrigation systems (e.g., recharging along a narrow strip in the middle of vineyard rows), alternate irrigation scheduling, and careful co-management of water, fertilizer and pesticide application [67,86]. Integration of multiple approaches may be required for successful operation, yet, current research on such dual objectives in agricultural irrigation is extremely limited.…”