In a normal year, groundwater accounts for 40 percent of California’s water supply. That number jumps to 60 percent during a drought. It’s also critically important for sustaining certain types of aquatic, terrestrial and coastal ecosystems.

Yet decades of unregulated groundwater withdrawal has compromised that ability to provide for people and nature. Wells dry up, water quality declines, and rivers, wetlands, and springs disappear.

To address this problem, California passed legislation requiring that groundwater basins be managed sustainably. We still face gaps, however, in our understanding of how to manage these basins to ensure the health of the ecosystems they support. Conservancy scientists are working with water managers and state agencies to close those gaps.

Science in Action

Freshwater | Science

Groundwater Dependent Ecosystems

How can we manage groundwater to benefit both people and nature?

Freshwater | Technology | Science

Groundwater for Ecosystem Health

How much groundwater do ecosystems need to survive?

2023 | Freshwater | Terrestrial | Planning | Science | Publications & Reports

Informing waterfowl conservation by determining what habitats are least resilient during times of drought

Erin E. Conlisk, Kristin B. Byrd, Elliot Matchett, Austin A. Lorenz, Michael Casazza, Gregory H. Golet, Mark D. Reynolds, Kristin A. Sesser, and Matthew E. Reiter

Landscape-scale wetland conservation requires understanding how wildlife responds to dynamic freshwater habitat availability. This study examined this for dabbling ducks by comparing habitat…

2022 | Freshwater | Terrestrial | Science | Publications & Reports

Potential Lithium Extraction in the United States: Environmental, Economic, and Policy Implications

Sophie S. Parker, Bradley Franklin, Brian S. Cohen, Melissa M. Rohde, Michael Clifford, Andrew Williams

Climate change will cause severe financial, social, and environmental upheaval if a massive reduction in carbon emissions is not achieved by 2030. To address this challenge, rechargeable lithium-ion…

2022 | Freshwater | Terrestrial | Planning | Science | Publications & Reports

Informing shorebird conservation by determining when and how much habitat is needed in wet and dry years

Gregory. H. Golet, Kristen. E. Dybala, Matthew. E. Reiter, Kristin. A. Sesser, Mark Reynolds, Rodd Kelsey

Shorebirds have declined precipitously in North America in the last 50 years, primarily due to the loss of wetlands. Incentive programs that pay farmers to create temporary wetland habitat on idled…

2022 | Freshwater | Planning | Science | Publications & Reports

A Machine Learning Approach to Predict Groundwater Levels in California Reveals Ecosystems at Risk

Melissa M. Rohde, Tanushree Biswas, Ian W. Housman, Leah S. Campbell, Kirk R. Klausmeyer, Jeanette Howard

Groundwater dependent ecosystems (GDEs) are increasingly threatened worldwide, but the shallow groundwater resources that they are reliant upon are seldom monitored. In this study, the researchers…

2022 | Freshwater | Planning | Science | Maps & Webmaps

SAGE: Shallow Groundwater Estimation Tool

Melissa M. Rohde, Tanushree Biswas, Ian W. Housman, Leah S. Campbell, Kirk R. Klausmeyer, Jeanette Howard

Groundwater dependent ecosystems (GDEs) are critical habitats throughout California that rely on shallow groundwater. Unfortunately, only a small subset of wells provide monitoring data for shallow…

2022 | Freshwater | Planning | Science | Publications & Reports

Groundwater dependence of riparian woodlands and the disrupting effect of anthropogenically altered streamflow

Melissa M. Rohde, John C. Stella, Dar A. Roberts, Michael Bliss Singer

This study combines satellite, groundwater, and streamflow data over a 5 year period (2015-2020) to understand the impacts of groundwater depth and streamflow alteration on groundwater-dependent…

2022 | Freshwater | Science | Publications & Reports

Functional Flows in Groundwater-Influenced Streams: Application of the California Environmental Flows Framework to Determine Ecological Flow Needs

Sarah M. Yarnell, Ann Willis, Alyssa Obester, Ryan A. Peek, Robert A. Lusardi, Julie Zimmerman, Theodore E. Grantham, Eric D. Stein

Very few rivers have protections to protect flow for species and ecosystems, in part because of the complexity and resources required to develop ecological flow criteria - the amount of water needed…

2021 | Freshwater | Terrestrial | Planning | Technology | Science | Publications & Reports

Planting Stormwater Solutions: A methodology for siting nature-based solutions for pollution capture, habitat enhancement, and multiple health benefits

Kelsey Jessup, Sophie S. Parker, John M. Randall, Brian S. Cohen, Rowan Roderick-Jones, Shona Ganguly, Jill Sourial

This paper presents results from Planting Stormwater Solutions, part of TNC’s Urban Conservation work in Los Angeles. The authors develop a methodology to prioritize siting of vegetated…

2021 | Freshwater | Terrestrial | Science | Publications & Reports

Biological responses to stream nutrients: A Synthesis of Science From Experimental Forests and Ranges

Kristen Wilson, Dale W. Johnson, Douglas F. Ryan, ed.

Authored by TNC staff and colleague, Chapter 8 of this report synthesizes environmental monitoring and studies performed at Sagehen Experimental Forest that are relevant to water quality regulatory…

2021 | Freshwater | Terrestrial | Science | Publications & Reports

Cannabis farms in California rely on wells outside of regulated groundwater basins

Christopher Dillis, Van Butsic, Jennifer Carah, Samuel Zipper, Theodore Grantham

Water management practices for cannabis farming in California are not well understood. This study examined permit reporting data and found that the vast majority (>75%) of permitted cannabis farms…

2021 | Freshwater | Planning | Science | Publications & Reports

Mind the Gaps: The Case for Truly Comprehensive Sustainable Groundwater Management

Barton H. Thompson, Jr., Melissa M. Rohde, Jeanette K. Howard, Sandi Matsumoto

In 2014, California’s landmark Sustainable Groundwater Management Act (SGMA) promised comprehensive management of California’s groundwater. This report, Mind the Gaps: The Case for Truly…

2021 | Freshwater | Terrestrial | Planning | Technology | Science | Data

Natural Communities Commonly Associated with Groundwater Version 2.0 (NCCAG 2.0)

Kirk Klausmeyer, Jeanette Howard, Melissa Rohde, Charlotte Stanley

The first step to sustainably manage groundwater dependent ecosystems (GDEs) is to identify where they are. The Nature Conservancy developed a statewide spatial database that provides locations of…

2021 | Freshwater | Planning | Maps & Webmaps

ICONS: Interconnected Surface Water in the Central Valley

Charlotte Stanley, Kirk Klausmeyer

This dataset categorizes the rivers and streams in the Central Valley on the likelihood that they are interconnected surface water (ISW) -- surface water hydraulically connected to groundwater. The…

2021 | Freshwater | Planning | Science | Publications & Reports

Managing Groundwater to Ensure Ecosystem Function

Laurel Saito, Bill Christian, Jennifer Diffley, Holly Richter, Melissa M. Rohde, Scott A. Morrison

In this paper, we describe minimum provisions for planning, managing, and monitoring groundwater in a manner that collectively can lower the risk of harm to groundwater-dependent ecosystems and…

2021 | Freshwater | Terrestrial | Planning | Science | Publications & Reports

Rewilding Agricultural Landscapes: A California Study in Rebalancing the Needs of People and Nature

H. Scott Butterfield, T. Rodd Kelsey, and Abigail K. Hart, Editors

As the world population grows, so does the demand for food, putting unprecedented pressure on agricultural lands. At the same time, climate change, soil degradation, and water scarcity mean that…

2021 | Freshwater | Terrestrial | Planning | Science | Publications & Reports

Predicting shorebird distributions in managed wetland habitats to inform where to implement habitat programs

Erin Conlisk, Gregory H. Golet, Mark D. Reynolds, Blake Barbaree, Kristin Sesser, Kristen Byrd, Sam Veloz, Matthew E. Reiter

Highly mobile species, such as migratory birds, respond to seasonal and yearly changes in resource availability by moving among habitats. Understanding how they select among habitats is important for…

2020 | Freshwater | Planning | Technology | Science | Publications & Reports

Base of fresh water, groundwater salinity and well distribution across California

Mary Kang, Debra Perrone, Ziming Wang, Scott Jasechko, Melissa M. Rohde

To ensure that California’s groundwater is sustainably managed in the future and over the long-term, current state definitions of what constitutes groundwater may need to be revised, according…

2020 | Freshwater | Terrestrial | Technology | Science | Publications & Reports

Conservation of Mojave Desert springs and associated biota: status, threats, and policy opportunities

Sophie S. Parker, Andy Zdon, William T. Christian, Brian S. Cohen, Maura Palacios Mejia, Naomi S. Fraga, Emily E. Curd, Kiumars Edalati, Mark A. Renshaw

This paper presents results from the Mojave Desert Springs research project, and discusses why the conservation of these groundwater-dependent ecosystems is so critical to biodiversity. The authors…

2020 | Freshwater | Terrestrial | Science | Publications & Reports

A meta-analysis contrasting active versus passive restoration practices in dryland agricultural ecosystems

M. Florencia Miguel, H. Scott Butterfield, Christopher J. Lortie

This meta-analysis provides a global synthesis of the which restoration practices – active vs. passive – are most successful at restoring plants, animals, and other ecosystem functions to…

2020 | Freshwater | Terrestrial | Technology | Science | Publications & Reports

The utility of environmental DNA from sediment and water samples for recovery of observed plant and animal species from four Mojave Desert springs

Maura Palacios Mejia, Emily Curd, Kiumars Edalati, Mark A. Renshaw, Roy Dunn, Daniel Potter, Naomi Fraga, Jenna Moore, Justin Saiz, Robert Wayne, Sophie S. Parker

This paper presents results from the Mojave Desert Springs research project. The authors used an environmental DNA (eDNA) technique to assess biodiversity at four naturally occurring springs. They…