Doctoral Dissertation Research: Understanding Intermittent Water Sources and Impacts on Fish to Design Optimal Water Conservation Strategies

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A major question in water resources is how to provide water for human uses while maintaining streamflow that sustains riverine ecosystems and fisheries. Intermittent streams, which provide habitat for salmonid fishes and water resources for agriculture, dry up into a series of disconnected pools in the late summer. To alleviate pressure on rivers and conserve habitat for juvenile salmon on the brink of extinction, communities are increasingly examining water conservation alternatives such as rainwater harvesting and groundwater recharge. Recent pilot projects provide a timely and unprecedented opportunity to address interdisciplinary questions about linkages among environmental variables, ecosystem services, and optimal management of increasingly scarce water resources. This project is expected to produce novel contributions to fundamental science, including understanding processes related to fish survival and the interactions among carbon decomposition, streamflow, and sediment transport in intermittent streams. By relating salmonid survival to predictable environmental characteristics and creating a better understanding of these critical variables, the research findings are likely to have applicability to seasonally dry watersheds region-and nation-wide. The project will facilitate mutually beneficial interactions between scientists and multiple stakeholder groups, who will also benefit from new e-tools for managing their natural resources. Findings will be disseminated through scholarly publications and at regional symposia as well as through documents developed for stakeholders and a citizen science web portal.This project specifically addresses a fundamental knowledge gap: what habitat conditions cause salmonids to disappear from some pools during the summer dry period? This project builds on a two-year field study in two tributaries of Salmon Creek (Sonoma Co., CA): Tannery Creek, which flows throughout the summer, and Fay Creek, which tends to dry into a series of isolated pools. Through extensive sampling in these adjacent streams, this research will test the hypothesis that accumulation of organic material in poorly flushed pools drives declining dissolved oxygen associated with a subsequent loss of salmonids. Fish surveys in the two tributaries will be paired with measurements of temperature, dissolved oxygen, water depth and velocity, pool volume, and organic carbon concentrations and quality. More intensive studies, focused on monitoring how these attributes change as the stream dries and determining which aquifers sustain sanctuary pools, will be conducted in four study river segments. Using linear mixing models, this research will quantify groundwater contributions and flowpaths to pools that provide critical refugia for salmon, and identify aquifers that should be targeted for enhanced infiltration. This work will also evaluate how rainwater harvesting will impact salmonid habitat with and without managed groundwater recharge. As a Doctoral Dissertation Research Improvement award, this project will provide support to enable a promising student to establish an independent research career. Increased understanding of interactions between groundwater and streamflow will enable residents and resource conservation districts to target water conservation and rainwater harvesting projects where they will yield the greatest benefit to stream ecosystems. Scientists working on salmonid recovery will benefit from increased access to local knowledge and observations via facilitated collaborative workshops and project-developed citizen science dissemination tools.