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Modeling functional flows in California rivers

March 1, 2022

Environmental flows are critical to the recovery and conservation of freshwater ecosystems worldwide. However, estimating
desired ranges of environmental flows across large, diverse landscapes is challenging. To advance protections of environmental flows for streams in California, USA, we developed a statewide modeling approach focused on functional components of the natural flow regime. Functional flow components in California streams—fall pulse flows, wet season peak flows and base flows, the spring flow recession, and dry season baseflows—support essential physical and ecological processes in riverine ecosystems. These functional flow components can be represented by functional flow metrics (FFMs) and quantified by their magnitude, timing, frequency, duration, and rate-of-change from daily streamflow records. After quantifying FFMs at reference-quality streamflow gages in California, we used machine-learning methods to estimate their natural range of values for all stream reaches in the state based on physical watershed characteristics and climatic factors. We found that the models performed well in predicting FFMs in streams across a diversity of landscape and climate contexts, according to several model performance criteria. Using the predicted FFM values, we established initial estimates of ecological flows that are expected to support critical functions and are broadly protective of ecosystem health. Modeling functional flows statewide offers a pathway for increasing the pace and scale of environmental flow protections in California and beyond.

Publication Year 2022
Title Modeling functional flows in California rivers
DOI 10.3389/fenvs.2022.787473
Authors Theodore E. Grantham, Daren Carlisle, Jeanette K. Howard, Belize Lane, Robert Lusardi, Alyssa Obester, Samuel Sandoval-Solis, Bronwen Stanford, Eric D. Stein, Kristine T. Taniguchi-Quan, Sarah M. Yarnell, Julie K. H Zimmerman
Publication Type Article
Publication Subtype Journal Article
Series Title Frontiers in Environmental Science
Index ID 70237373
Record Source USGS Publications Warehouse
USGS Organization WMA - Earth System Processes Division