Better understanding where water goes when it rains

Summary:

Understanding how rainfall becomes streamflow in a river or stored groundwater in an aquifer is critical to managing both water quality and quantity and developing groundwater sustainability plans that limit and address undesirable results. Yet our current knowledge base pertaining to the transformation of precipitation into streams and aquifers remains incomplete because of a lack of field-scale data. Quantifying where water that ends up in rivers and wells originates from, and the importance of intensive rainstorms on groundwater recharge will help decision-makers in California to better understand the potential ramifications of a more intense water cycle arising from climate change on groundwater recharge.

Investigator:

Scott Jasechko
Assistant Professor, Bren School of Environmental Science and Management
University of California, Santa Barbara

Project description:

Understanding how rainfall becomes streamflow in a river or stored groundwater in an aquifer is critical to managing both water quality and quantity and developing groundwater sustainability plans that limit and address undesirable results. Yet our current knowledge base pertaining to the transformation of precipitation into streams and aquifers remains incomplete because of a lack of field-scale data, limiting our ability to answer basic yet critical questions. These unsolved research questions are important to address in order to develop better predictions of streamwater and groundwater quality, pollutant fate and transport, and groundwater recharge rates.

This project launches a new long-term field study at the Jack and Laura Dangermond Preserve, located in coastal southern California, to address these questions by analyzing chemical tracers in rain, rivers, and groundwaters. Specifically, we are sampling and analyzing chemical ‘fingerprints’ of water (i.e., isotopes) to quantify where water that ends up in rivers and wells originates from, and how long these waters took to reach a location in an aquifer or a stream. Our research will also directly quantify the importance of intensive rainstorms on groundwater recharge, helping California to better understand the potential ramifications of a more intense water cycle arising from climate change on groundwater recharge.

Quantifying and predicting changes to groundwater recharge in a future and warmer climate is critical for developing Groundwater Sustainability Plans as part of the Sustainable Groundwater Management Act that account for the ongoing and expected changes to climate taking place over similar decadal-era timeframes, meaning the proposed place-based research has expected ramifications for water management well beyond the study watershed itself.