Lawrence Livermore National Laboratory

Isotope Hydrology:
New Approaches to Sustainable Water Management

Across California—from farms, to communities, to industry—water plays a vital role.

Yet managing this finite resource is a complex process that involves understanding where water comes from, how it moves through the environment, and how this precious resource is replenished. Information about this dynamic, complex system enables policymakers, water agencies, and other stakeholders to implement solutions aimed at meeting California’s need for clean, fresh water.

LLNL combines cutting-edge analytical techniques and expertise to deliver timely information regarding water management options to government entities, resource managers, industry partners, and other stakeholders.

LLNL scientists use isotope hydrology to trace the movement of water, which enables them to identify the sources of local fresh water, how quickly it is replenished, and whether it is at risk of contamination.

About Isotope Hydrology

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.

Chart showing the methods used to trace water throughout the hydrological cycle.View larger image

What we can learn

Isotopic analysis of surface water and groundwater can generate a broad range of data to facilitate informed decision making regarding how to address water management challenges, such as:

  • How fast water travels through an ecosystem, which can help identify where the geology supports fast flow paths that are beneficial for intentional, managed recharge of aquifers.
  • The age of existing groundwater, which helps explain trends in groundwater flow and geochemistry, and provides insight regarding future trends.
  • How groundwater interacts with surface water, including where and when those interactions occur, providing insight regarding the vulnerability of ecosystems that are dependent on groundwater.
  • How potential changes in groundwater management, such as altering flow paths, might impact the availability of future water resources.
  • The cause of any contamination or pollution detected in water sources.

Answering key questions

Stakeholders need actionable information that can help them answer questions like those provided below—and make informed decisions regarding managing future water needs.


  • What data do I need when making decisions regarding water management policies and legislation?
  • How will water management decisions impact groundwater reserves, wells, reservoirs, and other resources?

Water Resource Managers

  • Where does local groundwater come from, and how quickly is it replenished?
  • What risks threaten the local water supply, and how can I mitigate those risks?
  • Can I use managed aquifer recharge techniques to augment the local water supply?

Agricultural Stakeholders

  • How sustainable are water sources used for irrigation in a changing climate?
  • Over what time scale can we expect water management practices to improve water quality?

LLNL’s Unique Capabilities

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.

Graph of the isotope study results.


Peer-Reviewed Journal Papers

GAMA Special Studies Project Reports

LLNL was the project technical lead of the Special Studies Project, as part of the California Waterboards Groundwater Ambient Monitoring and Assessment Program. The Special Studies Project focused on specific groundwater quality studies, using state-of-the-art scientific techniques and methods that help researchers and public policy planners to better understand how groundwater contamination occurs and behaves. Since 2004, studies have focused on sources of nitrate, wastewater indicators, groundwater recharge, detection of pharmaceutical compounds and personal care products using low-level anthropogenic compounds as tracers, and isotopic composition as a contamination source tool. Expand the section below to view LLNL Special Studies reports to the Waterboards.

Excess nitrogen and methane in noble gas samples—April 2017

Tracers of Recent Recharge to Predict Drought Impacts on Groundwater: Mount Shasta Study Area—December 2016

Importance of River Water Recharge to Selected Groundwater Basins—May 2016

Distinguishing septic system and agricultural nitrate sources with stable isotope compositions and trace organic compounds: An investigation of nitrate sources in Chico, CA—August 2015

Identifying Paleowater in California Drinking Water Wells—July 2015

Development of a Capability for Analysis of Krypton-85 in Groundwater Samples—June 2015

Executive Summary: Recommendations on Model Criteria for Groundwater Sampling, Testing, and Monitoring of Oil and Gas Development in California—June 2015

Recommendations on Model Criteria for Groundwater Sampling, Testing, and Monitoring of Oil and Gas Development in California—June 2015

Application of multi-tracer methods to determine age distribution in nitrate-contaminated wells—March 2015

Seasonal variation of high elevation groundwater recharge as indicator of climate response—November 2014

Geostatistical analysis of groundwater age and other noble gas derived parameters in California groundwater—October 2014

Stable Isotopic Composition of Boron in Groundwater—San Diego County Domestic Well Data—February 2013

Interpretation of Isotopic Data in the Sonoma Valley, California—November 2012

Water and Nitrate Isotopic Data for San Diego County—November 2012

Noble Gas Membrane Inlet Mass Spectrometry: A Rapid, Low-Cost Method to Determine Travel Times at Recharge Operations Using Noble Gas Tracers—September 2012

Source Determination of Nitrate in Groundwater using Nitrogen, Oxygen, and Boron Isotopes: San Diego County GAMA Domestic Well Project–June 2012

Stable isotopic composition of boron in groundwater - analytical method development–October 2011

Nitrate Fate and Transport in the Salinas Valley–March 2011

Nitrate and Water Isotopic Data for Tulare County–January 2011

Ion exchange and trace element surface complexation reactions associated with applied recharge of lowTDS water in the San Joaquin Valley, California–August 2010

An isotopic and dissolved gas investigation of nitrate source and transport to a public supply well in California’s Central Valley–May 2010

Groundwater Age Simulation and Deconvolution Methods for Interpretation of 3H-3He Data–March 2010

Tracking Water Quality Changes during Groundwater Banking at Two Sites in San Joaquin County–November 2009

Evaluation of Noble Gases Recharge Temperatures in a Shallow Unconfined Aquifer–August 2009

Impact of Dairy Operations on Groundwater Quality–August 2009

Development of a Field Deployable Dissolved Gas Extraction Apparatus–September 2008

Impact of Artificial Recharge on Dissolved Noble Gasses in Groundwater in California–January 2008

Field-based Study of Septic System Impact on Groundwater (A Feasibility Study)—September 2007

Fate and Transport of Wastewater Indicators: Results from Ambient Groundwater and from Groundwater Directly Influenced by Wastewater–June 2006

Sources and Transport of Nitrate in Groundwater in the Livermore Valley Basin, California–November 2005

Sources and Transport of Nitrate in Shallow groundwater in the Llagas Basin of Santa Clara County, California–July 2005

Denitrification in a Shallow Aquifer Underlying a Dairy Farm: New Approaches to Characterization and Modeling–2004

Interpretation of Tritium-3Helium Groundwater Ages and Associated Dissolved Noble Gas Results from Public Water Supply Wells in the Los Angeles Physiographic Basin–December 2002

Contact Us

LLNL’s Isotope Hydrology Group includes experts in hydrology, reactive transport, radiochemistry, nuclear counting, and mass spectrometry. Rooted in more than five decades of national leadership in environmental radiochemistry, our multidisciplinary team studies water management scenarios and delivers timely answers to sponsors, academic and industry partners, and other stakeholders.

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Richard Bibby

Staff Scientist


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Amanda Deinhart

Staff Scientist


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Amy Gryshuk

Strategic Engagements


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Erik Oerter

Staff Scientist


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Michael Singleton

Staff Scientist


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Ate Visser

Staff Scientist


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