Groundwater Dependent Ecosystems

How can we manage groundwater to benefit both people and nature?

A riparian forest in the upper Santa Clara River (Ventura County, CA) during a 5-year drought (2011-2016). Trees died when groundwater levels fell below the rooting depth of the trees. © Kirk Klausmeyer/TNC

Groundwater is a hidden resource, occurring almost everywhere beneath the land surface. Groundwater is critically important to Californians, supplying 40% of the state’s water supply in normal years and much more in dry years.

Groundwater also plays a vital role for nature. Where groundwater reaches the surface, it can provide a reliable source of water for wildlife, which is especially important in places where surface waters are seasonally scarce. For some plant species, groundwater serves as the only source of water year-round. It can also replenish rivers and streams that would otherwise run dry in late summer, making it possible for iconic species like steelhead and salmon to survive.

Applying our science

Groundwater dependent ecosystems, or GDEs, are ecological communities of species that depend on groundwater for survival. These ecosystems support a diverse array of plants and animals, including many rare and endangered species here in California. GDEs were largely unstudied in the state until 2010 when Conservancy scientists comprehensively catalogued and mapped these unique ecosystems. The resulting study revealed that all 515 of California’s groundwater basins harbor GDEs.

California is the only only state to specifically recognize the needs of nature in its groundwater law.

In 2014, California enacted the Sustainable Groundwater Management Act (SGMA), landmark legislation that established a framework for sustainable management of groundwater basins. Although California was the last state to pass comprehensive groundwater legislation, it is the only state to specifically recognize GDEs – and the needs of nature – in its groundwater law.

Under SGMA, delivering groundwater for human uses is not enough; local groundwater sustainability agencies are also tasked with identifying and considering GDEs in their Groundwater Sustainability Plans. To assist agencies with their planning process, the Conservancy and partners at California Department of Water Resources and California Department of Fish and Wildlife updated the 2010 GDE study to provide a current statewide map of seeps and springs, wetlands, and vegetation that are likely to depend on groundwater.  

Since many groundwater sustainability agencies are con­sidering GDEs for the first time, the Conservancy created a step-by-step guide using the best available science to help them set thresholds to sustainably manage groundwater. With partners in the Fox Canyon Groundwater Management Agency in Ventura County, the Conservancy is testing and refining these tools with local practitioners through the development of one of the first groundwater sustainability plans in the state. Fox Canyon will then provide a blueprint for other agencies on how to incorporate nature in thier plans. 

Vegetation and habitats can die off when groundwater drops too deep or too fast. Infographic: © http://groundwatercalifornia.org/


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2017 | Freshwater | Planning | Science | Publications & Reports

A Global Synthesis of Managing Groundwater Dependent Ecosystems Under Sustainable Groundwater Policy

Melissa M. Rohde, Ray Froend, Jeanette Howard

Groundwater is a vital water supply worldwide for people and nature. However, species and ecosystems that depend on groundwater for some or all of their water needs, known as groundwater dependent ecosystems (GDEs), are increasingly becoming threatened worldwide. This paper provides an overview of how…

2016 | Freshwater | Science | Publications & Reports

Groundwater and Stream Interaction in California’s Central Valley: Insights for Sustainable Groundwater Management

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,…

2015 | Freshwater | Data

Groundwater Dependent Ecosystems in California data

Jeanette Howard, Matt Merrifield

The California Freshwater Species Database is the first comprehensive geospatial database of California’s freshwater species compiled and standardized into single format from nearly 500 sources. It provides a single source for geodata covering the plants and animals that rely on California’s freshwater resources to survive.

2016 | Freshwater | Maps & Webmaps

How and Where Nature Uses Groundwater

Kirk Klausmeyer, Jeanette Howard, Sandi Matsumoto, Sally Liu, Melissa Rohde

Groundwater is essential to the health and viability of plants, animals and ecosystems. Many tree species, like willows and cottonwoods, rely on groundwater to survive seasonal and annual dry spells. Fish and other aquatic life need groundwater to keep rivers flowing. When unsustainable management causes groundwater levels…

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,…

2010 | Freshwater | Publications & Reports

Mapping Groundwater Dependent Ecosystems in California

Jeanette Howard, Matt Merrifield

In 2014 the California legislature passed a three-bill package (SB 1168, AB 1739, and SB 1319) of groundwater reform legislation that was the most significant update of California water policy in several decades. The legislation provides authorities and guidance for local agencies to develop sustainable…

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