2021-2022 Executive Summary
Ecohydrology is the study of how changes to flow patterns impact the health of aquatic ecosystems. Streams, wetlands and other aquatic environments all experience routine natural variation in the timing, magnitude, duration and frequency of flows. While aquatic life has naturally adapted to these flow patterns, human activities can trigger significant disruptions to flows that alter the natural structure and composition of aquatic ecosystems. California’s water resources management community needs to understand the relationship between alterations to environmental flows and ecological impacts to 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 research is helping 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, changes in flow, and related physical and biological responses, 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 management actions, including stream restoration, 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 2021-22 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 refine the recently released “beta” version of the Streamflow Duration Assessment Method (SDAM) for the Arid West, while also supporting the development 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 supporting agencies that seek to incorporate SDAMs into their programs (i.e., through the creation of training programs and data management and visualization tools).
- 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 climate change effects, and evaluation of water use and reuse proposals. SCCWRP is conducting investigations focused on the effects of flow management in three Southern California watersheds (Los Angeles River, San Juan Creek and Aliso Creek), with a goal of informing stormwater and wastewater management actions (including reuse) and stream restoration. These projects will help develop recommended 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. These projects represent important early implementations of the recently developed California Environmental Flows Framework (CEFF) for Southern California urban watersheds. SCCWRP also is applying flow-ecology principles to assess hydrologic vulnerability of all coastally draining streams in the San Diego region in an effort to help inform basin planning and management in the region.
- 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.