Instream Flow Studies

Through human activities, such as dams and diversions, the flow regime of many streams has been modified from original conditions—particularly in the western U.S. In order to predict impacts and negotiate flow regimes for proposed projects, instream flow modeling is conducted using procedures originally developed by the U.S. Fish & Wildlife Service and continued by the U.S. Geological Survey. These models incorporate field measurements of appropriate depth, velocity, and substrate characteristics at multiple sites/transects/points in a stream at multiple flows. These data are used to construct a hydraulic model of the stream to predict changes in depth and velocity and compare to habitat suitability curves for relevant fish species. The results are predicted changes in “useable” area.