Beta version of stream flow classification tool released, to be rolled out across U.S. Southwest

Posted January 29, 2021

SCCWRP and its partners have completed development of the beta version of a tool that can rapidly distinguish among perennial, intermittent and ephemeral streams in the U.S. Southwest, paving the way for its initial rollout across an area stretching from California to Texas.

The flow duration classification tool, which was submitted in December to the U.S. Environmental Protection Agency, uses easily observable field indicators – including presence of wetland vegetation and specific types of aquatic insects – to classify streams based on the duration of their surface flows. The Streamflow Duration Assessment Method tool is a collaboration of SCCWRP, USEPA and the U.S. Army Corps of Engineers.

Ephemeral streams are water bodies that experience surface flows only after rain events, whereas intermittent streams experience sustained seasonal flows from snow melt and groundwater.

The tool is designed to support regulatory programs that require stream flow duration classifications, including a recent federal rule change that relies on stream flow duration to identify Waters of the United States.

SCCWRP and its partners will begin training state and federal agencies in the tool’s use in the coming months. The tool’s beta version will be used for one year, then finalized for use across the Arid Southwest region.

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