Groundwater-dependent ecosystems (GDE's) are communities of species that depend on groundwater for survival and support a diverse array of plants and animals. Policies such as the Sustainable Groundwater Management Act (SGMA) require local sustainability plans to protect these sensitive species and habitats. Is this framework working?
SESSION CHAIRS Dr. Nicholas P Murphy1, Dr. Bruce K. Orr2
1The Nature Conservancy, Sacramento, CA, United States. 2Stillwater Sciences, Berkeley, CA, United States
Dr. Nicholas Murphy
The Nature Conservancy
As the Senior Groundwater Scientist for the California Water Program at The Nature Conservancy, Nick provides technical and scientific leadership regarding the importance of the interconnection between surface water and groundwater resources. Nick works closely with staff and partners to inform policies, regulations, and on-the-ground projects that integrate groundwater and surface water management to support riverine and groundwater dependent ecosystems.
Dr. Bruce K. Orr
Stillwater Sciences
Bruce is an ecologist interested in ecological restoration and factors affecting the vegetation and habitat dynamics of riparian and wetland ecosystems in the western United States. He helped cofound Stillwater Sciences in 1996 and has been a member of the California Native Plant Society Vegetation Committee since 1993.Bruce is an ecologist specializing in ecological restoration and the vegetation and habitat dynamics of riparian and wetland ecosystems across the western United States. He co‑founded Stillwater Sciences in 1996 and has served on the CNPS Vegetation Committee since 1993.
11.1 Developing and Implementing Ecological Thresholds for Groundwater Dependent Ecosystems Under the Sustainable Groundwater Management Act (SGMA) of California
Dr. Nicholas P Murphy1, Dr. Melissa Rohde2, Bridget Gibbons1, Caitrin Chappelle1, Taylor Broadhead3
1The Nature Conservancy, Sacramento, CA, United States. 2Rohde Environmental LLC, Seattle, WA, United States. 3Audubon, Oakland, CA, United States
Description Groundwater dependent ecosystems (GDEs) provide critical ecosystem services, serve as climate refugia, and are biodiversity hotspots. The Sustainable Groundwater Management Act (SGMA), passed in 2015, requires the development and implementation of groundwater sustainability plans by 2040. As a beneficial user of groundwater, GDEs must be considered in the development of groundwater sustainability goals. The implementation of ecological thresholds (groundwater levels necessary to maintain healthy GDE) has emerged as a novel strategy for integrating ecosystem needs into sustainable groundwater management. The development of ecological thresholds aims to prevent ecosystem degradation due to declining groundwater levels. In this study, Normalized Difference Vegetation Index (NDVI) data and groundwater level data are paired to identify the groundwater levels at which GDE health declines significantly. By correlating NDVI trends with groundwater fluctuations, practitioners can recommend threshold values that reflect the minimum groundwater elevation required to sustain ecosystem function. These thresholds can then be used to inform the setting of sustainable management criteria in Groundwater Sustainability Plans (GSPs).  Insights from recent technical assistance and engagement in Sacramento Valley groundwater subbasins highlight the opportunity and the complexity of operationalizing ecological thresholds within GSPs under SGMA to prevent undesirable results to GDEs.
Presenter Bios
Dr. Nicholas Murphy
The Nature Conservancy
As the Senior Groundwater Scientist for the California Water Program at The Nature Conservancy, Nick provides technical and scientific leadership regarding the importance of the interconnection between surface water and groundwater resources. Nick works closely with staff and partners to inform policies, regulations, and on-the-ground projects that integrate groundwater and surface water management to support riverine and groundwater dependent ecosystems.
11.2 Identifying Critical Groundwater Thresholds for Riparian Ecosystem Health and Management: Putting Science into Practice
Dr. Jared Williams1, Dr. Christopher Kibler2, Dr. John C Stella3, Dr. Bruce Orr4, Dr. Christian Braudrick4, Dr. Dar Roberts2, Dr. Michael Singer2,5
1University of California, Santa Barbara, University of California at Santa Barbara Marine Science Institute Santa Barbara, CA, United States. 2University of California at Santa Barbara, Santa Barbara, CA, United States. 3SUNY College of Environmental Science and Forestry, Syracuse, NY, United States. 4Stillwater Sciences, Berkeley, CA, United States. 5Cardiff University, Cardiff, Wales, United Kingdom
Description Groundwater-dependent riparian ecosystems (GDEs) maintain high levels of biomass, biodiversity, and structural complexity compared to other dryland plant communities. The high levels of plant growth are facilitated by shallow groundwater, which provides a persistent source of hydration throughout the dry growing season. When groundwater elevations decline, however, plant root systems can lose access to the water table, which often results in stress and mortality for water-sensitive riparian tree species. Water management policies, such as the Sustainable Groundwater Management Act (SGMA), are beginning to explicitly recognize ecosystem needs when developing water allocation strategies. However, implementing these policies effectively requires an understanding of critical groundwater thresholds for ecosystem health. In this study, we synthesized stable isotope measurements, remote sensing data of plant health, and measurements from groundwater monitoring wells to identify these thresholds. We examined GDEs in the Santa Clara River floodplain in Ventura County. The stable isotope measurements revealed that Populus and Salix spp. increased their groundwater consumption as precipitation decreased during drought. When groundwater elevations subsequently declined, there was a rapid onset of physiological stress as trees lost access to the water table. The remote sensing measurements revealed widespread tree mortality when groundwater depths exceeded 5 meters. Collectively, our findings provide critical insights into the sensitivity of riparian ecosystems to groundwater conditions. We briefly summarize how these findings are now being translated into groundwater management policies through SGMA. For example, results from this study were used to set minimum thresholds for GDEs in the Fillmore and Piru Subbasins.
Presenter Bios
Dr. Jared Williams
University of California, Santa Barbara
Jared is a plant ecologist interested in how climate change affects dryland vegetation communities. Jared’s work has applied stable isotopes, ecophysiological measurements, and modeling approaches to evaluate the responses of dryland riparian forests to rising temperatures and increasingly severe droughts. With a strong passion for ecological restoration, Jared aims for his research to inform effective restoration practices that improve ecosystem resilience in the face of climate change.
11.3 What Is Lost and What Is Left: The Role of Alkali Meadow in the Retelling of the Owens Valley Water Story
Emily Ontiveros
Friends of the Inyo, Bishop, CA, United States
Description The story of Los Angeles’ water grab in the Eastern Sierra is well known, but the common narrative often leaves out several important aspects. The impacts of water extraction are ongoing, management is dynamic and thus capable of changing, and groundwater-dependent vegetation plays an important role. After decades of legal battles and technical monitoring, the relationship between water management and vegetation has become obscured. Water wars have turned into legal and scientific wars, where investigation into management practices can have the unintentional effect of getting lost in technicalities and ignoring questions about the premise of managing water to sustain ecosystems. The 1991 Inyo-LA Long Term Water Agreement sets forth a system of managing groundwater and monitoring vegetation, yet questions and controversy remain about the use of a degraded baseline, the response of alkali meadow to a declining water table, and the intersection of policy such as the Sustainable Groundwater Management Act.
In a situation where technical experts answer directly to the agencies involved, tribes and local communities have been pushed out of a process that shapes almost every aspect of their lives and the landscape. For the Owens Valley, the path to more sustainable water management requires a retelling of the water story and an increased understanding of the critical role of groundwater dependent ecosystems. This entails education and outreach, connecting science to community through concepts like translational ecology, and building people’s relationships to ecosystems that need to be protected and restored.
Presenter Bios
Emily Ontiveros
Friends of the Inyo
Emily Ontiveros is a Water Empowerment Organizer with Friends of the Inyo, working to strengthen community understanding of the water systems that shape the lives and landscapes of the Eastern Sierra. She has a Master’s in Landscape Architecture from the University of New Mexico and has experience in ecological restoration, community engagement, and resource management. From site to regional scales, she is interested in the relationships between people and water in the west and aspires to find more opportunities for meaningful connection and ecological uplift.
11.4 Restoring Hydrologic Function and Ecological Integrity in Upper Lacey Meadow: Early Outcomes from a Multi-Phase Restoration Project
Dr. Shannon M. Still, Robbie Lee, Dr. Sara Grove, and Matt Wacker
H.T. Harvey & Associates, Los Gatos, CA, United States
Description The Lacey Meadows Restoration Project aims to restore meadow habitat and stream channel function in the Webber Lake watershed, northwest of Truckee, CA. In 2023, the Truckee River Watershed Council (TRWC), in partnership with the Truckee Donner Land Trust (TDLT) and Balance Hydrologics, implemented Phase 1 in Upper Lacey Meadow, which rerouted Lacey Creek to its historic channel, installed grade control structures to encourage channel aggradation, and created pilot channels to direct creek flows onto the meadow surface during snowmelt and other high-flow conditions in Lacey Creek.
Baseline ecological monitoring by H.T. Harvey & Associates in 2021 compared to post-project monitoring in 2024 and 2025 shows promising early results. Wet meadow has been restored at four permanent plots. Indicators include a 20% reduction in bare ground, shallower saturation depths, and increased soil mottling. Vegetation composition shifted toward higher-functioning species, with a 20% increase in plants that have a high-status as indicators for a wetland environment and greater presence of rhizomatous graminoids, including spike bentgrass (Agrostis exarata), tufted hairgrass (Deschampsia cespitosa), and Baltic rush (Juncus balticus).
Pre-restoration conditions reflected hydrologic degradation, drought stress, and impacts of historic land uses. Post-restoration improvements are attributed to both hydrologic interventions and modified grazing practices, which have reduced browsing pressure and promoted root development.
These findings suggest successful hydrologic recovery, with vegetation and soil responses underway. Continued monitoring and adaptive management will be key to supporting long-term ecological resilience.
Presenter Bios
Dr. Shannon M. Still
H.T. Harvey & Associates
Dr. Shannon Still is a senior plant ecologist and project manager at H.T. Harvey & Associates in the Sacramento Valley office, with a couple of decades of experience in California botany. His botanical expertise spans taxonomy, phylogenetics, and rare plant conservation, with a focus on Papaveraceae, Malvaceae, and Rosaceae. Shannon serves on the CNPS Rare Plant Program Committee and studies Eschscholzia taxonomy, biogeography, and species distribution modeling in the context of climate change.
11.5 Using the California Environmental Flows Framework to Evaluate Aquatic and Riparian GDEs: Napa Valley Subbasin, CA
Christian Braudrick
Stillwater Sciences, Berkeley, CA, United States
Description Both riparian and aquatic groundwater dependent ecosystems (GDEs) in the Napa Valley Subbasin are dependent on shallow groundwater to maintain surface flow and groundwater within the rooting depth of GDEs. They are particularly susceptible to groundwater pumping and climate change. GDEs occur throughout the Napa Valley Subbasin, with surface flows strongly tied to groundwater elevation during the dry season. Monitoring shows that the mainstem Napa often goes dry, with some reaches supporting year-round flow, while others transition to isolated pools or completely dry conditions during the summer. Widespread channel incision has made the Napa River less resilient to hydrologic changes.
As part of the Sustainable Groundwater Management Act, Groundwater Sustainability Agencies are required to consider GDEs when determining sustainable management criteria for the Subbasin. Because of the linkage between groundwater levels and summer low flows, we are applying the California Environmental Flows Framework (CEFF) to assess linkages between surface flow and habitat for GDEs at six intensive monitoring sites throughout the Subbasin. Monitoring at each of the six sites includes: groundwater elevation, surface water stage, special status plants, groundwater-dependent vegetation health, bird species, fish surveys, fish habitat, and aquatic wildlife. We are adapting CEFF to also assess the hydrologic requirements of riparian GDEs. The results at intensive sites will be expanded using hydrological modeling coupled with the results of the CEFF analysis to inform sustainable management criteria for the Subbasin.
Presenter Bios
Christian Braudrick
Stillwater Sciences
Christian is a geomorphologist at Stillwater Sciences in Berkely, CA. He has led their groundwater dependent ecosystems work under the Sustainable Groundwater Management Act (SGMA). His work at Stillwater ranges from geomorphic assessments, stream restoration, and groundwater dependent ecosystems. He particularly likes working on interdisciplinary problems.
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DateThursday, February 5
