California is one of the most hydrologically altered landscapes in the world. As water becomes ever more scarce and the human population continues to grow, that vast engineered system strains to meet the needs of people let alone the needs of nature. 

Water rights allocations far exceed actual surface water supply, and millions of wells tap groundwater to meet the increasing demands of farms and communities. As groundwater reservoirs are depleted they can in turn reduce surface flows – exacerbating a vicious cycle in which people and nature both lose. Rivers, wetlands and groundwater-dependent ecosystems are caught in this struggle for an increasingly limited resource. Nearly half of California’s roughly 4,000 freshwater species are considered vulnerable to extinction. Of the taxa that are found nowhere but California – our endemic freshwater biodiversity – 90 percent are at risk.

But there is hope. While it is impossible to return natural flows to most of California’s rivers and streams, we can – through science, technology, and innovative market tools – endeavor to deliver water when and where nature needs it most.

Groundwater

In a normal year, groundwater accounts for 40 percent of California’s water supply. That number jumps to 60… >>

Surface Flows

Californians have fundamentally altered many of the state’s rivers and streams with dams, pipes, and diversions, and the… >>

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 | Technology | Economics | Science

Dynamic Conservation

In an era of rapid global change, how can conservationists provide habitat where and when nature needs it most?

2018 | Freshwater | Terrestrial | Science | Publications & Reports

Wetland Bird Conservation in California Rice Fields

Chris Elphick, T. Rodd Kelsey, Catherine Hickey, Khara Strum, Paul Buttner, Monica Iglecia

Wetland birds, especially Sandhill Cranes, are heavily dependent on irrigated farmlands in the Central Valley of California after widespread conversion of natural habitats. TNC and its partners have had great success working with farmers to design and implement compatible management practices that make sure farms,…


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

Groundwater sustainability in the San Joaquin Valley: Multiple benefits if agricultural lands are retired and restored strategically

Rodd Kelsey, Abby Hart, H. Scott Butterfield, Dan Vink

Restoring habitat in retired farmland could reduce water demand and provide ecosystem services for farmers and local communities. In some areas of California, as a result of the Sustainable Groundwater Management Act (SGMA), it is likely that large amounts of agricultural land will need to…


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 | Marine | Planning | Science | Publications & Reports

Conserving California's Coastal Habitats: A Legacy and a Future with Sea Level Rise

Walter N. Heady, Brian S. Cohen, Mary G. Gleason, Joshua N. Morris, Sarah G. Newkirk, Kirk R. Klausmeyer, Hilary R. Walecka, Elizabeth Gagneron

Sea level rise presents a new challenge to coastal conservation. The authors quantified and mapped the vulnerability of habitats, imperiled species, and conservation lands to sea level rise throughout the entire California coast, where high biodiversity, high endemism, and 26.5 million people coincide. Combining habitat…


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

Better late than never: a synthesis of strategic land retirement and restoration in California

Chris Lortie, Alex Filazzola, Rodd Kelsey, Abigail Hart, Scott Butterfield

Over the past 100 years, California's Central Valley has undergone a massive transformation from desert to a mosaic of farmland and urban development. This transformation has also meant many desert species have lost habitat. Now, new groundwater regulations are calling for the retirement of more…


2018 | Freshwater | Economics | Publications & Reports

California’s First Farmer-Led Groundwater Market

Sarah Heard, E.J. Remson, Siobhan King, Sandi Matsumoto

The Conservancy has a vested interest in preserving farms in Ventura County because they buffer important river and wetland habitat from nearby urban lands. In western Ventura County, over 70% of groundwater use is agricultural. Due to requirements of the Sustainable Groundwater Management Act (SGMA), this use will…


2018 | Freshwater | Terrestrial | Science | Publications & Reports

Impact of extreme drought and incentive programs on flooded agriculture and wetlands in California’s Central Valley

Matthew E. Reiter​, Nathan K. Elliott, Dennis Jongsomjit, Gregory H. Golet, Mark D. Reynolds

In the Central Valley of California, with 90% of the historic wetlands gone, waterbirds depend upon managed wetlands and seasonally flooded agriculture to meet their habitat needs. The 2013-2015 drought in the Central Valley was more severe than drought years during 2000-2011 and reduced waterbird…


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 spillover dynamics of organisms from urban to natural landscapes

Jill E. Spear, Erik K. Grijalva, Julia S. Michaels, Sophie S. Parker

This paper discusses the impact of urban-dwelling plants and animals on regional wildland populations, both within and across species. The authors reviewed the global conservation literature and identified seven ecological processes that have the potential to be affected by spillover from urban to wildland areas.…


2018 | Freshwater | Science | Microsite

Groundwater Resource Hub

Sandi Matsumoto, Gregg Werner, Melissa Rohde, Kirk Klausmeyer

Groundwater dependent ecosystems (GDEs) are plant and animal communities that require groundwater to meet some or all of their water needs. GDEs provide important benefits to California including habitat for animals, water supply, water purification, flood mitigation, erosion control, recreational opportunities and enjoyment of California’s…


2018 | Freshwater | Planning | Publications & Reports

A freshwater conservation blueprint for California: prioritizing watersheds for freshwater biodiversity

Jeanette K. Howard, Kurt A. Fesenmyer, Theodore E. Grantham, Joshua H. Viers, Peter R. Ode, Peter B. Moyle, Sarah J. Kupferburg, Joseph L. Furnish, Andrew Rehn, Joseph Slusark, Raphael D. Mazor, Nicholas R. Santos, Ryan A. Peek, Amber N. Wright

Freshwater ecosystems are in peril globally. Threats to freshwater biodiversity are numerous and include habitat degradation, pollution, overexploitation, dam construction, species invasion, and hydroclimatic change. With conservation resources often limited, prioritization tooks are needed by land and water managers. To fill this need, the authors…


2018 | Freshwater | Science | Publications & Reports

Mojave Desert Springs and Waterholes: Results of the 2015-16 Mojave Desert Spring Survey

Prepared by Andrew Zdon & Associates Inc. for Transition Habitat Conservancy, The Bureau of Land Management, and The Nature Conservancy

The Mojave Desert within California, which spans four counties, exists as one of the most important ecological regions in the southwestern United States. Both the groundwater and surface water in the region support isolated, unique and diverse ecosystems, while also supporting human needs through domestic,…


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 | Planning | Science | Publications & Reports

Harnessing cross-border resources to confront climate change

Aburto-Oropeza, O., M. Edwards, S. Butterfield, and 93 additional authors

The U.S. and Mexico face many shared ecological changes due to the increased frequency and severity of droughts and rising energy demands; trends that entail economic costs for both nations and major implications for human well-being. This paper synthesizes current knowledge about the most pressing issues…


2018 | Freshwater | Science | Publications & Reports

Groundwater Dependent Ecosystems under the Sustainable Groundwater Management Act: Guidance for Preparing Groundwater Sustainability Plans

Rohde, M.M., S. Matsumoto, J. Howard, S. Liu, L. Riege, E.J. Remson

California's Sustainable Groundwater Management Act (SGMA) of 2014 is landmark legislation that empowers local agencies, known as groundwater sustainability agencies, to sustainably manage groundwater resources for social, economic and environmental benefits. SGMA also includes specific requirements to identify and consider impacts to groundwater dependent ecosystems (GDEs).…


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…