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 | Terrestrial | Science

Rewilding the San Joaquin Valley

40 years of science sets the course for the largest recovery of species in U.S. history

Freshwater | Terrestrial | Marine | Science

Research for Impact

How do we design scientific research to have impact in the world?

2022 | Freshwater | Terrestrial | Publications & Reports

Restoration richness tipping point meta-analysis: finding the sweet spot

Christopher J. Lortie, Maria Florencia Miguel, Alessandro Filazzola, Harry Scott Butterfield

Climate change, drought, and water scarcity are driving major land transformations in dryland ecosystems globally. Historically these ecosystems have been disproportionately degraded due to widespread agricultural conversion. Because of these pressures, there are significant opportunities for rewilding and restoration of these dryland ecosystems. This global…


2022 | Freshwater | Terrestrial | Marine | Planning | Technology | Science | Maps & Webmaps

The Mitigation Wizard

Carrie Schloss, Liz O’Donoghue, Dan Rademacher, Patric Huber, Jodi McGraw, Kim Becerril, Janine Knapp

Every year, infrastructure agencies and developers spend hundreds of millions of dollars to mitigate for impacts to sensitive species and habitats. These mitigation sites are often piecemeal projects, which can result in islands of mitigation. Regional advance mitigation programs seek to change this paradigm so…


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 used satellite-based remote sensing, climate data, and machine learning to predict groundwater levels over a 35 year period (1985…


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 groundwater. This tool, developed for a publication in Frontiers in Earth Science, uses satellite data and machine learning tools to…


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

The Guidebook for FEMA Hazard Mitigation Grants: Promoting Nature-Based Mitigation Through FEMA Mitigation Grants

The Nature Conservancy, AECOM

With increase in devasting storms and wildfires due to climate change, we need solutions to help mitigate the impact. Traditionally, “gray” or “hard” infrastructure solutions that rely on engineering projects using concrete and steel have dominated efforts to manage risk and mitigate hazard impacts…


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 vegetation across California. The study shows that deeper groundwater levels resulted in poor vegetation health, but that current water management…


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 | Terrestrial | Marine | Science | Publications & Reports

Transforming Palmyra Atoll to native-tree dominance will increase net carbon storage and reduce dissolved organic carbon reef runoff

Kate Longley-Wood, Mary Engels , Kevin D. Lafferty, John P. McLaughlin, Alex Wegmann

Native forests on tropical islands have been displaced by non-native species, leading to calls for their transformation. Simultaneously, there is increasing recognition that tropical forests can help sequester carbon that would otherwise enter the atmosphere. At Palmyra Atoll, efforts are underway to transform the rainforest…


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,…


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

Conservation Science Catalyst Fund - 2021 Annual Report

Brynn Pewtherer, Scott Morrison

The Nature Conservancy deploys science to help overcome major challenges facing people and nature. In today’s fast-paced world, turning threats to nature into opportunities for conservation requires agility. The Conservation Science Catalyst Fund enables our science team to mobilize quickly — and produce the information…


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 | Science | Publications & Reports

Integrating citizen science data with expert surveys increases accuracy and spatial extent of species distribution models.

O.J. Robinson, V. Ruiz-Gutierrez, M.D. Reynolds, G.H. Golet, M. Strimas-Mackey and D. Fink

Information on species’ habitat associations and distributions, across wide spatial and temporal scales, is fundamental for guiding conservation. Yet these data are often in short supply. In recent years citizen science data, such as that derived from eBird, has increasingly become available to fill…


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 | 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 agencies. Water quality in the basin is mainly controlled by groundwater emerging in springs, but wildland fires,…


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

Coastal Adaptation Vision for Naval Base Ventura County Point Mugu: Technical Report

Environmental Science Associates (ESA) for The Nature Conservancy and Naval Base Ventura County


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…