2022-2023 Executive Summary
Ecohydrology is the study of how changes to flow patterns impact 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 impacts 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 solving complex flow management issues. By developing tools and strategies that help managers evaluate various potential options for offsetting threats to environmental flows, SCCWRP is poised to help 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 patterns in key drivers of hydrologic change (e.g., land use, climate change, water use practices), (2) develop tools including statistical and deterministic models to evaluate the relationship between key drivers and changes in flow and related physical and biological responses in the stream, and (3) evaluate the effectiveness of various management actions (e.g., BMPs) and other efforts to reduce or mitigate the impacts of flow modification. Evaluating possible management actions includes developing mechanisms that enhance performance and that improve understanding of how multiple BMPs can work synergistically across broad areas to improve the condition of receiving waters.
This year, SCCWRP will continue to focus on developing tools that can be used to predict how changes in flow translate to changes in physical structure and in biological community composition – and how these changes affect water resources management decisions. SCCWRP’s focus for 2022-2023 will be on:
- Assessing flow duration to understand the extent of aquatic resources: SCCWRP will continue working to help watershed managers in the Arid West and beyond understand the extent of their aquatic resources by developing critically needed tools that enable streams to be classified by their flow duration (i.e., as perennial, intermittent, or ephemeral). SCCWRP will continue to support rollout and implementation of the recently released “beta” version of the Streamflow Duration Assessment Method (SDAM) for the Arid West, while also supporting development and implementation of comparable tools for other regions of the United States, including the Western Mountains, the Great Plains, Alaska and Hawaii. SCCWRP’s efforts will focus not just on SDAM development, but also on creation of training programs and data management and visualization tools for agencies that are seeking to incorporate SDAMs into their programs.
- 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 recently developed 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 will inform 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 will be able to use these flow ecology analyses and insights to take informed actions in areas like wastewater recycling, stormwater capture and stream restoration.
- Evaluating the effectiveness of hydromodification management: SCCWRP is developing a framework for evaluating the effectiveness of hydromodification management actions aimed at restoring and maintaining the physical and biological health of Southern California streams. Although sufficient management actions have occurred to begin evaluating the efficacy of recent hydromodification management approaches and the tools used to inform management decisions, comprehensive monitoring data at the appropriate temporal and spatial scales are rarely collected, limiting the capacity to evaluate performance effectiveness. Thus, SCCWRP is conducting a regional field survey of Southern California streams, which were previously surveyed 15 years ago, to identify the appropriate monitoring timeframe, frequency, and spatial extent necessary for assessing performance effectiveness. SCCWRP will also develop recommendations to restructure monitoring programs and to standardize approaches for assessing performance effectiveness. Information compiled through these efforts will also be used to determine any necessary refinements to the hydromodification screening and assessment tools previously developed by SCCWRP and its partners.
- Advancing species modeling for informing environmental flow recommendations: SCCWRP is advancing the science of species occurrence and distribution modeling by applying this science to several southern California case studies. SCCWRP is drawing on previously developed statistical approaches that relate changes in flow to effects on biological communities (especially benthic invertebrates and algae). Concurrently, SCCWRP is exploring new hybrid statistical and mechanistic approaches for conducting assessments that enable proposed flow alterations to be evaluated in terms how they affect higher trophic communities, such as fish, amphibians, and birds, and piloting their application to inform environmental flow decisions. These initial models, which focus on flows within the Los Angeles River watershed, will be further developed to include stream temperature and evaluation of the effects of multiple stressors on biological communities in multiple watersheds. SCCWRP also intends to further expand these models to include consideration of interactions between physical modification of stream channels and flow alteration.