Californians have fundamentally altered many of the state’s rivers and streams with dams, pipes, and diversions, and the State is home to some of the world’s most complex water delivery projects. As an unfortunate consequence, habitat for many freshwater species has been degraded or destroyed.

But, is it necessary to tradeoff the freshwater needs of birds, fish, and other species against the needs of farms and cities? Could freshwater flows be managed to better mimic the dynamics of their unimpaired past, dynamics to which native species have adapted and need to persist? And how should climate change considerations be incorporated into water management, to enhance the resilience of freshwater systems for both people and nature?

Our science is focused on tackling these questions.

Science in Action

Freshwater | Science

Restoring California’s Largest River

How can we restore large rivers and floodplains to benefit nature and people?

Freshwater | Terrestrial | Science

Not Leaving it to Beaver

Can we restore meadows by mimicking beavers?

2024 | Freshwater | Terrestrial | Science | Publications & Reports

Potential Impacts to Biodiversity from Proposed Lithium Extraction in Nevada and California

Michael J. Clifford, Sophie S. Parker, Laurel Saito, Brian S. Cohen, Naomi S. Fraga

Lithium batteries are important for the clean energy transition in the United States because they are used in electric vehicles and for grid power storage. However, lithium extraction may have impacts on biodiversity. The authors use data from a previous TNC study to analyze…


2024 | Freshwater | Terrestrial | Publications & Reports

Potential impacts of proposed lithium extraction on biodiversity and conservation in the contiguous United States

Sophie S. Parker, Michael J. Clifford, Brian S. Cohen

To address climate change, the United States is incentivizing the production of electric vehicles containing domestically derived lithium batteries. Extracting this lithium may have environmental impacts, including impacts on biodiversity. To reveal what these impacts could be, the authors mapped 72 proposed lithium extraction…


2024 | Freshwater | Terrestrial | Publications & Reports

Expert bioblitz on the Atwood Preserve

Michael Clifford, Sophie Parker, Matt Rader, Lydia Bailey, Naomi Fraga, Chris Hass, Estella Hernandez, Jan Kempf, Lois Merkler, Michael Swink

The Amargosa River supports one of the most outstanding suites of endemic and imperiled species in the world. In 2019, TNC acquired the Atwood Preserve in the river’s headwaters, the management of which could impact river flows, condition, and biodiversity. With the support of the…


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

Nature-Based Solutions for Urban Stormwater Management

Kristina Kreter, Shona Ganguly, Rowan Roderick-Jones, and Kelsey Jessup

New strategies to address urban runoff management with nature-based approaches offer promising solutions to alleviating climate change impacts—like urban heat, water shortages, and floods—and environmental pollution and the loss of natural green space that diminish the quality of life for vulnerable communities. Vegetated…


2023 | Freshwater | Microsite

Drought Flows Monitor

Julie Zimmerman, Jennifer Carah, Kirk Klausmeyer, Gabe Rossi, Mia Van Docto, Jeanette Howard, Charlie Schneider, Matt Clifford, Monty Schmitt

Drought conditions are occurring with more frequency, greater severity, and longer duration under climate change. Human water use compounds the effects of drought, further stressing California’s ecosystems, impacting farms, rural communities and urban water supplies. The Salmon and Steelhead Coalition developed a Drought Flows Monitor…


2023 | Freshwater | Terrestrial | Marine | Planning | Economics | Publications & Reports

Valuing the Flood Reduction Benefits of Marsh Restoration

Taylor-Burns, R., Heard, S., Beck, M. W.

There is growing evidence for the beneficial role that wetlands can play in reducing flood risk, but in many urban estuaries, coastal development has resulted in dramatic habitat loss and fragmentation. In the past several decades, marsh restoration has emerged as a core management objective…


2022 | Freshwater | Science | Publications & Reports

Water balance for gaged watersheds in the Central Sierra Nevada, California and Nevada, United States

James W. Roche, Kristen N. Wilson, Qin Ma, Roger C. Bales

This study evaluated the water balance components of precipitation, evapotranspiration, discharge, and change in storage compared to measured streamflow and unregulated streamflow estimates in the central Sierra Nevada. The fifty-two watersheds varied in size and in elevation. This study found that the evapotranspiration estimates plus gridded…


2022 | Freshwater | Terrestrial | Technology | Economics | Science | Publications & Reports

Developing an adaptive management approach to cowbird control on the Santa Clara River, California

Sophie S. Parker, Linnea S. Hall, Mary J. Whitfield, Laura Riege, Kathryn R. Selm, René Corado

This paper presents results from a field-based study that can be used to benefit songbirds in riverside habitats like those found along the Santa Clara River in Ventura County, California. Songbirds such as the Least Bell’s Vireo suffer population declines in part because Brown-headed…


2022 | Freshwater | Science | Publications & Reports

Water Resources Allocation and Agriculture: Allocations and Environmental Flows

Eric D. Stein, Michael E. McClain, Ashmita Sengupta, Theodore E. Grantham, Julie K.H. Zimmerman, Sarah M. Yarnell

In this chapter of Water Resources Allocation and Agriculture, the authors provide insights on how to integrate environmental flows into water allocation for agriculture across the world. They argue that holistic environmental flows approaches that are fully protective of ecosystem needs and integrate surface and…


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 batteries will play a key role in transitioning the energy and transportation sectors away from fossil fuel…


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

Quantity and fate of synthetic microfiber emissions from apparel washing in California and strategies for their reduction

Roland Geyer, Jenna Gavigan, Alexis M. Jackson, Vienna R. Saccomanno, Sangwon Suh, Mary G. Gleason

Synthetic microfibers are the most prevalent type of microplastic and apparel washing is a major source of microfiber pollution. Using California as a case study to estimate the magnitude of microfiber emissions and evaluate mitigation approaches, the authors estimate that in 2019 over 4,850,000 pounds (2.2…


2022 | Freshwater | Science | Publications & Reports

Hydraulic Properties of the Riffle Crest and Applications for Stream Ecosystem Management

Gabriel Rossi, Darren Mierau, Jennifer Carah

A simple stream depth measurement at the deepest part of a riffle crest in a river or stream provides an easy-to-measure and inexpensive metric for ecological researech, environmental flow management, and habitat assessment. This paper describes measurement methods, as well as ways to use riffle measurements…


2022 | Freshwater | Technology | Science | Publications & Reports

Modeling Functional Flows in California’s Rivers

Theodore E. Grantham, Daren M. Carlisle, Jeanette Howard, Belize Lane, Robert Lusardi, Alyssa Obester, Samuel Sandoval-Solis, Bronwen Stanford, Eric D. Stein, Kristine T. Taniguchi-Quan, Sarah M. Yarnell, Julie K. H. Zimmerman

Protecting water in rivers is made more challenging by the lack of quantitative estimates of the amount of water required to protect river ecosystems. The authors developed a model and made quantitative predictions of the amount of flow needed for five key functional flow components,…


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 in rivers to protect ecosystems. The authors applied the California Environmental Flows Framework,…


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

Sacramento River: balancing ecological and social restoration goals to restore riparian habitat along a lowland floodplain river, California, USA

Case study by: K.D. Holl, G.H. Golet

Advancing conservation requires understanding the constraints imposed on natural systems by human societies. This understanding typically comes from engagement with local stakeholders, as opposed to from scholastic training. A recent textbook on restoration ecology by Karen Holl seeks to alleviate this problem by providing real-world…


2021 | Freshwater | Science | Publications & Reports

The California Environmental Flows Framework: Meeting the Challenges of Developing a Large-Scale Environmental Flows Program

Eric D. Stein, Julie Zimmerman, Sarah M. Yarnell, Bronwen Stanford, Belize Lane, Kristine T. Taniguchi-Quan, Alyssa Obester, Theodore E. Grantham, Robert A. Lusardi, Samuel Sandoval-Solis

The first step to protecting rivers is figuring out how much water they need to protect species and ecological functions - known as ecological flow criteria. Scientists have struggled to develop flow criteria to protect species and ecosystems across large regions, which means the vast…


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 nature-based solutions for stormwater capture so that these projects maximize benefits to biological diversity, social and public…


2021 | Freshwater | Terrestrial | Marine | Planning | Science | Video

StoryMap: Restoring coastal wetlands for climate resilience: A case study at Naval Base Ventura County Point Mugu

Charlotte Stanley, Alyssa Mann, Walter Heady

The United States operates thousands of military installations in the U.S. and worldwide, worth about $1.2 trillion. These facilities are where personnel train and test weaponry, with the specific aim of ensuring the nation’s security. With climate change, coastal installations are now being impacted by rising sea levels, erosion and…


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

Restoring coastal wetlands for climate resilience: A case study at Naval Base Ventura County, Pt. Mugu

Walter Heady, Alyssa Mann, Stacey Solie, Bob Battalio, James Jackson, Kendall Lousen, and Bob Barnes

The U.S. Congress and the Department of Defense (DoD) have determined that climate change is a threat to national security and have required military installations to develop plans to improve the climate resilience of both military installations and key supporting civilian infrastructure. This report, co-authored…


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 use groundwater wells to source water, with many wells located outside regulated groundwater basins. Groundwater pumping…