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?

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 | 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 | 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…


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 | 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…


2021 | Freshwater | Science | Maps & Webmaps

California Natural Flows Webapp

Julie K.H. Zimmerman, Daren M. Carlisle, Jason T. May, Kirk R. Klausmeyer, Theodore E. Grantham, Larry R. Brown, Jeanette K. Howard, Nathaniel Rindlaub, Falk Schuetzenmeister

Water is essential for California’s people, economy, and environment. Centuries of water management through dams and diversion have altered the flows in many streams and rivers, which can harm the freshwater ecosystems. The Nature Conservancy and the United States Geological Survey (USGS), and other partners…


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 dataset includes information on the average, maximum, and minimum depth to groundwater, using groundwater elevation…


2020 | Freshwater | Science | Publications & Reports

Evaluating and Protecting Environmental Water Assets: A Guide for Land Conservation Practitioners

Author: Chris Alford, Editors and Reviewers: Amy Campbell, Monty Schmitt, Sara Press, Wendy Eliot, Bob Neale

Evaluating and Protecting Environmental Water Assets: A Guide for Land Conservation Practitioners, a publication by TNC and the Sonoma Land Trust (SLT), provides provides easy to understand guidance, resources, and tools that California land trusts, open space districts, resource conservation districts, and others can…


2020 | Freshwater | Marine | Science | Microsite

State of Salmon in California

Sally Liu, Megan Webb, Jeanette Howard, Jennifer Carah

Chinook, coho and steelhead were once tremendously abundant in most of California’s major rivers and streams. As recently as the 1960s, salmon and steelhead were so plentiful in streams that horses would get spooked trying to cross. Due to water damming and diversions, habitat degradation and…


2020 | Freshwater | Science | Publications & Reports

A functional flows approach to selecting ecologically relevant flow metrics for environmental flow applications

Sarah M. Yarnell, Eric D. Stein, J. Angus Webb, Theodore Grantham, Rob A. Lusardi, Julie Zimmerman, Ryan A. Peek, Belize A. Lane, Jeanette Howard, Samuel Sandoval-Solis

The authors of this paper are engaged in developing flow criteria for California Streams through California Environmental Flows Framework (CEFF) collaboration. The effort is funded by the State Water Resources Control Board. This collaboration is a working group within the California Water Quality Monitoring Council. This…


2019 | Freshwater | Planning | Science | Publications & Reports

Dynamic multibenefit solutions for global water challenges

Melissa M. Rohde, Mark Reynolds, Jeanette Howard

In this article, the authors provide an example of how dynamic multi-benefit solutions used to provide “pop-up” wetland habitat for migratory birds also replenishing depleted aquifers to create environmental and water supply benefits and broadens it to the global scale. Additionally, this article outlines six…


2019 | Freshwater | Science | Publications & Reports

Cannabis and residential groundwater pumping impacts on streamflow and ecosystems in Northern California

Samuel C. Zipper, Jennifer K. Carah, Christopher Dillis, Tom Gleeson, Ben Kerr, Melissa M. Rohde, Jeanette K. Howard, Julie K.H. Zimmerman

Using a newly developed tool for estimating streamflow depletion from groundwater pumping, this study examined the impacts of ongoing groundwater pumping on streamflow and aquatic ecosystems in the Navarro watershed in rural, coastal California. The study found that common uses of groundwater in the watershed,…


2019 | Freshwater | Terrestrial | Science | Publications & Reports

First known survey of cannabis production practices in California

Houston Wilson, Hekia Bodwitch, Jennifer Carah, Kent Daane, Christy Getz, Theodore E. Grantham, Van Butsic

Cannabis has been an industry in the shadows for many decades and little studied. In partnership with U.C. Berkeley and U.C. Cooperative Extension, the Conservancy staff developed the first cannabis growers survey on cultivation practices in California. The goal of the survey was to understand…


2019 | Freshwater | Science | Publications & Reports

Rapid and Accurate Estimates of Streamflow Depletion Caused by Groundwater Pumping Using Analytical Depletion Functions

Samuel C. Zipper, Tom Gleeson, Ben Kerr, Jeanette K. Howard, Melissa M. Rohde, Jennifer Carah, Julie Zimmerman

Reductions in streamflow from groundwater pumping can negatively impact water users and aquatic ecosystems but are challenging to estimate due to the time and expertise required to develop numerical models often used in water management. This paper develops a new approach – a combination of…