Flood-MAR

Motivating Question: How can we efficiently model nature-based Flood-MAR approaches to many watersheds in the San Joaquin Valley in California?

California faces both drought and flood extremes. To reduce the impacts of drought while guaranteeing protection from flooding, the California Department of Water Resources (CA DWR) has established the Flood-Managed Aquifer Recharge (Flood-MAR) program, which encourages districts and landowners to divert flood water for aquifer recharge. By using existing agricultural land, Flood-MAR could be considered as an EWN solution. Preliminary Flood-MAR analyses suggest that if California could capture excess surface waters during winter storms, it could significantly address chronic and decades-long overdraft of groundwater aquifers underlying the irrigated fields in the Central Valley. However, doing so requires that local farmers opt into an increased use of working lands for recharge in the few weeks where flood waters are available—essentially having farmers apply any excess water to their fields at just the right times, so as to recharge aquifers while maintaining crop yield and growth. This would restore some of the natural floodplains in the San Joaquin Valley, while still allowing crops to be grown. Combined with actions now required by California’s Sustainable Groundwater Management Act (SGMA), local Groundwater Sustainability Agencies (GSAs) are more actively considering all recharge options to avoid forced fallowing of agricultural lands. Given this increased interest in integrated surface water and groundwater, the CA DWR is leading a cross agency/industry/academia effort to better identify the required data, science, and tools needed to implement Flood-MAR throughout California. Quantifying the benefits of Flood-MAR will advance the Corp’s portfolio of EWN solutions. 

To address this need, we model different Flood-MAR scenarios in the Merced River basin in California, whose water resources are managed by the Merced Irrigation District through the Lake McClure reservoir. We are building on the CA DWR Flood-MAR Reconnaissance Study now underway in this area by proposing a light-touch, highly scalable approach to the analysis. We compare our results to the ongoing DWR study and recommend a means of efficiently ensuring transferability of the approach, without building out the entire analytics that were used by CA DWR.