Groundwater for Ecosystem Health

How much groundwater do ecosystems need to survive?

The Cosumnes River Preserve in the Central Valley of California. Photo:    Photo: © Karen Gregg Elliott/TNC

When California enacted the Sustainable Groundwater Management Act (SGMA) in 2014 it was the last state to pass comprehensive groundwater legislation, but was the first and only state to specifically require that the needs of nature be included in the management of groundwater. In addition to balancing the needs of people and nature, groundwater sustainability agencies (GSAs) must identify and consider the groundwater needs of ecosystems.  

But how? And how much groundwater do ecosystems need? What thresholds must be maintained for plants and animals to survive?

Applying our science

The Cosumnes River Preserve in California’s Central Valley is a complex of properties purchased by the Conservancy and partners beginning in 1984. The early goal of the Preserve was to expand riparian forests by protecting and restoring floodplain ecosystems. For the past two decades, Conservancy scientists have investigated the linkages between riparian forest health, groundwater and surface water.   

Through the years, the Conservancy and partners launched groundwater and vegetation monitoring programs to identify optimal management for conditions to maintain a healthy ecosystem. Through years of observation, they hypothesized that groundwater was playing a larger role than previously thought. Today, we are tapping these long-term studies to see how groundwater conditions are linked to the health of the ecosystem above ground.

In 2017, in partnership with Lawrence Berkeley National Laboratory, Conservancy scientists dug a little deeper at the Cosumnes by employing a geophysical approach to take “x-rays” of the ground to detect groundwater. The images revealed that the healthiest forests had the greatest access to groundwater–supporting their hypothesis.

This on-the-ground research in the Cosumnes couples biological and hydrological datasets to determine the groundwater thresholds and baseline conditions required to sustain ecosystem health. This is the type of information GSAs need to sufficiently and successfully include nature in their plans required under SGMA.

Geophysical approaches that help us “see” groundwater are helping to characterize groundwater conditions under forests. Warmer colors indicate dry sands and cooler colors indicate wet silts and clays.


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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…

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…

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,…

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