How it works
Isotope hydrology involves the use of environmental isotopes to trace the movement of water throughout the hydrological cycle, from precipitation, through surface runoff and evaporation, to the flow of surface water and groundwater.
As water molecules move through this cycle, they are naturally tagged with isotopic “fingerprints,” offering clues about the water’s origin and its history of movement.
Hydrologists can use these naturally occurring isotopic tracers to map sources of groundwater, identify how quickly water resources are recharged (replenished), and determine the risk of saltwater intrusion or other contamination. In addition, noble gas tracers can be introduced into managed aquifer recharge facilities or aquifer storage and recovery wells to provide detailed information regarding the flow rates in the aquifer and the recovery of recharged water.
LLNL’s comprehensive suite of analytical techniques enables our scientists to study a broad range of water management challenges across the hydrological cycle. Our experts collect water samples and use one-of-a-kind, high-precision mass spectrometry and nuclear counting facilities at LLNL to conduct isotopic analyses of the samples. We also develop new isotope tracer techniques to understand evolving water management challenges.
LLNL Analysis of San Joaquin Valley Groundwater Recharge
With funding from the California State Water Resources Control Board, LLNL scientists used isotope hydrology to study a groundwater basin in the south-eastern portion of the San Joaquin Valley and understand how this important water resource is replenished.
Investigators learned that river water provides nearly 50% of the groundwater recharge in this predominantly agricultural area. However, this recharge mechanism fluctuates significantly throughout the year, as the major source of river water is snowmelt from the Sierra Nevada mountains. In addition, all of the region’s major rivers are dammed, and water is diverted for agricultural irrigation and drinking water in other parts of California.
Based on their findings, LLNL scientists recommended groundwater banking of seasonal surface water, along with expansion of managed aquifer practices, to increase the resilience of San Joaquin Valley’s water system.
