View SCCWRP’s full thematic Research Plan for Ecohydrology (PDF)
2025-2026 Executive Summary
Ecohydrology is the study of how changes to flow patterns affect the health of aquatic ecosystems. Streams, estuaries, wetlands and other aquatic environments all experience routine natural variation in the timing, magnitude, duration and frequency of flows. But human activities also can trigger significant disruptions to flow patterns that alter the structure and composition of aquatic ecosystems. California’s water resources management community needs to understand the ecological consequences of these alterations to environmental flows, so managers can make optimal decisions about how to impound, divert, recharge and otherwise control the release of water to serve a variety of societal needs – from flood control to agricultural irrigation to water recycling. SCCWRP is working to help water resources managers take science-informed approaches to making complex flow management decisions. By developing tools and strategies that help managers evaluate various potential options for offsetting threats to environmental flows, SCCWRP is helping to bring greater consistency, standardization, and coordination to the design of environmental flow management programs across California.
SCCWRP’s ecohydrology research is driven by three major objectives: (1) Understand and predict hydrologic change in response to natural and anthropogenic drivers (e.g., land use, climate change, water use practices), (2) develop tools, including statistical and deterministic models, to evaluate the relationship between changes in hydrology, physical habitat (e.g., sediment-flux and channel form) and biologically relevant water-quality parameters (e.g., temperature, turbidity, specific conductance) to biological response in streams, and (3) evaluate the effectiveness of various management actions (e.g., BMPs) and other efforts to reduce or mitigate the impacts of flow modification. Effectiveness assessment includes development of user-friendly decision support tools and case studies that demonstrate implementation of ecohydrology management actions.
This year, SCCWRP will continue to focus on developing tools that can be used to predict how changes in flow (and temperature) translate to changes in physical structure and in biological communities – and how these changes affect water resources management decisions. SCCWRP’s focus for 2025-2026 will be on:
- Applying flow-ecology to water resources management: SCCWRP is continuing to examine how to apply flow-ecology principles to optimally support water resources management, including urban stormwater and dry-weather flow management, evaluation of hydrologic vulnerability and climate change effects on long-term basin planning and management, and evaluation of water use and reuse proposals. SCCWRP’s work to answer pressing flow management questions for watersheds in Southern California and beyond is being guided by the California Environmental Flows Framework (CEFF), a standardized, multi-step approach for evaluating the environmental flow needs of California streams and balancing these needs with recreational uses and other beneficial uses. The findings and insights from this work are informing development of environmental flow targets that sustain the health of freshwater fish, amphibians and riparian habitats, while also optimally balancing competing demands on finite water resources, especially reuse of treated wastewater effluent discharges and enhanced stormwater capture practices. Stormwater and wastewater managers are able to use these flow ecology analyses and insights to take informed actions in areas such as wastewater recycling, stormwater capture and stream restoration. SCCWRP is also exploring the application of combinations of natural and nature-based solutions as part of a suite of management approaches aimed at managing flow and temperature modifications to meet habitat and species needs through both modeling and pilot implementation of innovative strategies.
- Advancing ecological modeling for informing environmental flow and temperature management: SCCWRP is advancing the science on how changes in flow and temperature affect species occurrence and survival. SCCWRP is drawing on previously developed statistical approaches that relate changes in flow to effects on biological communities (especially benthic invertebrates and algae) and applying these approaches to higher trophic level organisms, such as fish and amphibians. Then, SCCWRP is adapting these methods to support risk-based decisions that allow managers to evaluate probabilities of effect at various levels of alteration, instead of establishing static flow or temperature targets. SCCWRP intends to further expand these models to include consideration of interactions between physical modification of stream channels and flow alteration.
- Improving understanding of flow-ecology and temperature-ecology relationships in arid, ephemeral streams: Determining flow and temperature ecology relationships in arid, ephemeral streams is particularly challenging due to their flashy nature, extremely low (or absent) flows, and potential reliance on groundwater contributions. SCCWRP will advance the assessment and modeling of dry-season low flows using machine learning methods that build on past statewide modeling efforts. SCCWRP will also explore mechanisms to account for the contribution of shallow groundwater (vadose zone) on streamflow and temperature to better account for their influence on flow-ecology and temperature-ecology relationships.
- Developing approaches to consider effects of flow and temperature management on human uses: SCCWRP is developing strategic partnerships with economists and social scientists to develop and test approaches that can quantify how changes in ecological conditions associated with flow and temperature management affect human uses, such as recreation, aesthetics and cultural uses. These methods will provide managers with the opportunity to more directly consider these effects and examine how to balance multiple water resources management objectives. Future efforts will incorporate these tools into multi-criteria decision support systems.
