The value of water in the face of a changing climate has scrambled arid climate states, like California (CA), to take a hard look and develop surface water – groundwater legislation to ensure this vital resource into the future. CA water is vital to maintain its agricultural economy but also providing enough drinking water for its quickly growing population while maintaining and honoring existing water rights. The current CA SGMA regulations are forcing CA water agencies to expand, improve, and develop new groundwater management approaches such as Flood-MAR whereby, river water is diverted during the winter high flows onto fallow – dormant agricultural fields to recharge the shallow aquifers. Water agencies are faced with many challenges in developing a sustainable groundwater management plan that has led to many knowledge gap questions for instance: 

1. Where does the water go and does it make it to the aquifer? 
2. What is the rate of recharge and how much infiltrated to the aquifer? 
3. What is the quality of the infiltrated water and is that quality maintained in the subsurface?
4. What is the structure of the subsurface geology and does it improve or hinder desired recharge potential?

Here in LBNL’s Geophysics group we are combining traditional geophysical methods with novel sensors and modeling codes to help answer these questions across scales. Some examples include a) time-lapse monitoring of water infiltration through the subsurface to the unconfined aquifer and quantifying recharge  volumes during flooding events, b) Understanding the controls on riverbed clogging to ensure peak performance at a riverbank filtration facility, c) Understanding post fire effects on water quality at riverbank filtration facility, d) Evaluating and optimizing urban green infrastructure (drywells, bioswales, infiltration galleries, etc.) recharge potential to feed data into a user tool for recharge site assessment, and e) Understanding the link between a shallow aquifer and groundwater dependent ecosystems.