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?

2018 | Freshwater | Planning | Science | Maps & Webmaps

Rearing habitat objectives to support salmon in the Central Valley

Travis M. Hinkelman, Myfanwy Johnston, Joseph E. Merz, Julie Zimmerman

To restore degraded stream corridors and develop large-scale, sustainable watershed conservation strategies, it is essential for managers to consider—in order to ultimately re-establish—the habitat requirements of keystone species. For example, in order to restore salmon in the Central Valley of California, we need a clear…


2018 | Freshwater | Terrestrial | Planning | Science | Publications & Reports

Water Supply and Habitat Resiliency for a Future Los Angeles River: Site-Specific Natural Enhancement Opportunities Informed by River Flow and Watershed-Wide Action

Brian Cohen, Shona Ganguly, Sophie Parker, John Randall, Jill Sourial, and Lara Weatherly of The Nature Conservancy, Land IQ, Natural History Museum Los Angeles County, WRC Consulting Services Inc., Travis Longcore, University of Southern California, Connective Issue, Inc.

As a basic principle of ecological systems, a watershed’s hydrology determines the flow characteristics of its river system. These flows define what the biological characteristics of that river will be, which in turn determine what kinds of habitat enhancement projects will succeed at various locations along…


2018 | Freshwater | Terrestrial | Planning | Science | Publications & Reports

Ecological Values of the Amargosa River in California

Sophie S. Parker, Jim Moore, Leonard Warren

The 185 mile-long Amargosa River, one of only two rivers with perennial flow in the California portion of the Mojave Desert, is fed by an ancient groundwater aquifer. The river provides habitat for hundreds of organisms, including a unique suite of rare, endemic, and imperiled…


2018 | Freshwater | Terrestrial | Marine | Planning | Science | Publications & Reports

Improving multi-objective ecological flow management with flexible priorities and turn-taking: a case study from the Sacramento River and Sacramento-San Joaquin Delta

Alexander C.A.D., F. Poulsen, D.C.E. Robinson, B.O. Ma , R.A. Luster

Management of the Sacramento River and Sacramento–San Joaquin Delta is one of California’s greatest challenges, requiring trade-offs between valued components that serve a multiplicity of conflicting purposes. This paper demonstrates an improved method for multiple-objective allocation of water based on a “turn-taking” optimization model. The…


2018 | Freshwater | Terrestrial | Science | Publications & Reports

Using ricelands to provide temporary shorebird habitat during migration

Gregory H. Golet, Candace Low, Simon Avery, Katie Andrews, Christopher J. McColl, Rheyna Laney, Mark D. Reynolds

Migratory birds face great challenges due to the climate change, conversion of historical stopover sites, and other factors. To help address these challenges, the Conservancy launched a dynamic conservation incentive program to create temporary wetland habitats in harvested and fallow rice fields for shorebirds…


2017 | Freshwater | Science | Data

California Natural Flows Database

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

The Nature Conservancy and the United Stated Geological Survey (USGS) partnered to generate estimates of natural flows (expected streamflow in the absence of human modification) in all the streams and rivers in California (1950-2015). For more details on the methods and results see  Patterns and…


2017 | Freshwater | Science | Publications & Reports

Managing diversions in unregulated streams using a modified percent-of-flow approach

Darren W. Mierau, William J. Trush, Gabriel J. Rossi, Jennifer K. Carah, Matthew O. Clifford, Jeanette K. Howard

The California water rights system often dis-incentivizes water management that benefits both nature and people by directing the timing of diversions to the summer when water is the most scarce. It makes more sense to divert water in the winter when it is plentiful, and…


2017 | Freshwater | Science | Publications & Reports

Patterns and magnitude of flow alteration in California, USA

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

The importance of the natural flow regime to stream and river health has received growing attention in recent years. Understanding natural flows and patterns of flow alteration is an important first step in improving the management of California’s rivers and streams for human and ecosystem…


2017 | Freshwater | Terrestrial | Economics | Publications & Reports

Market-Based Mechanisms For Securing Environmental Water In California

Sarah Heard, Siobhan King, Eric Hallstein

California’s water supply is becoming increasingly unreliable. During dry times, consumptive use often outstrips supplies. As a result, people and nature suffer. This imbalance of supply and demand will likely grow worse if future demand for agricultural and urban water increases alongside a warming climate.…


2017 | Freshwater | Terrestrial | Planning | Science | Publications & Reports

Population and habitat objectives for avian conservation in California’s Central Valley riparian ecosystems

Kristen E. Dybala, Neil Clipperton, Thomas Gardali, Gregory H. Golet, Rodd Kelsey, Stefan Lorenzato, Ron Melcer, Jr., Nathaniel E. Seavy, Joseph G. Silveira

The Conservancy and partners are working to establish riparian ecosystems that provide sufficient habitat to support genetically robust, self-sustaining, and resilient bird populations in California's Central Valley. In this study, researchers selected 12 riparian landbird focal species as indicators of riparian ecosystem health and are…


2017 | Freshwater | Terrestrial | Planning | Publications & Reports

Informing watershed planning and policy in the Truckee River basin through stakeholder engagement, scenario development, and impact evaluation

Kristen Wilson, Erik Lowe, Stacey Wolny, Barry Nickel , Rodd Kelsey

This study demonstrates how science-based planning with stakeholder input can improve and direct conservation investments across existing state and jurisdictional boundaries. The authors set out to help direct the type, amount, and location of conservaiton investments in the Truckee River watershed in the Sierra Nevada…


2017 | Freshwater | Planning | Publications & Reports

Water for nature: What we can do today to help California’s rivers, streams and wetlands

Burns, C.E., A. Hoss, N. Smith, K. Klausmeyer, K. Fesenmeyer, A. Campbell, J. Carah, E. Forsburg, S. Heard, J.K. Howard, L. Hulette, S. Liu, P. Spraycar, B. Stranko, G. Werner, D. Wordham

This report identifies a set of strategies that will have the greatest impact on environmental flows, and to provide a resource for conservation organizations, resource agencies, and other stakeholders in California that may help create the conditions that allow freshwater species to thrive well into…


2016 | Freshwater | Science | Publications & Reports

Benefits and Economic Costs of Managed Aquifer Recharge in California

Debra Perrone, Melissa M. Rohde

Managed aquifer recharge (MAR) projects can play an important role in ensuring California manages its groundwater sustainably. This study, the first to investigate the benefits and economic costs of MAR projects in the state, found California MAR projects to be a cost-effective storage strategy, exhibit a…


2016 | Freshwater | Terrestrial | Technology | Science | Publications & Reports

Pop-up wetland habitats benefit migrating birds and farmers

Christopher J. McColl , Katie Andrews, Mark Reynolds, Gregory H. Golet

In response to the decline of wetland habitats for migrating and wintering water birds in California, the Conservancy developed a program called BirdReturns that creates “pop-up” wetland habitat where and when birds need them most by enlisting farmers to flood their fields at specific times. This…


2016 | Freshwater | Science | Publications & Reports

Sustainable Groundwater Management: What We Can Learn from California's Central Valley Streams

The Nature Conservancy, RMC Consultants, Inc.

Groundwater is intimately connected to surface water, which has profound implications for sustainable water resource management. California has historically overlooked this important interaction and as a consequence, decisions about groundwater extractions have generally failed to address the resulting impacts to aquatic ecosystems such as rivers,…