2023 Early Hearing Detection & Intervention Conference

March 5-7, 2023 • Cincinnati, OH

5/21/2018 | 9:45 AM - 10:00 AM | FLOW ALTERATION AND FUNCTIONAL FLOW METRICS FOR CALIFORNIA STREAMS | 410 B

FLOW ALTERATION AND FUNCTIONAL FLOW METRICS FOR CALIFORNIA STREAMS

Managing streamflows for ecological outcomes requires understanding the natural flow regime, the current flow regime, and flows needed to achieve ecological objectives. We utilized machine learning statistical models to predict natural monthly flows for all stream reaches in California from 1950 to 2015. We compared observed flows measured at 540 stream gages across the state with modeled natural flows at the same locations, to quantify flow alteration over the past 20 years. We found that 95% of gages in California had at least one month of altered flows and 11% of all gages were altered over 66% of months. Most gages exhibited both flow inflation (flows higher than expected) and depletion (flows lower than expected). Inflation was most prevalent during summer while flow depletion occurred year-round. Depleted monthly flows averaged 20% of expected natural flows, while inflated flows averaged 10 times natural. The modeling approach will be used to predict natural functional flow metrics for every stream in California to inform environmental flow management. Prediction intervals around these metrics will be used to establish initial statewide environmental flow recommendations that can be refined according to management needs and ecological objectives.

Modeling
Flow
Dams

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Presenters/Authors

Julie Zimmerman (), The Nature Conservancy, julie.zimmerman@tnc.org;