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<br />~ drifting; low-power boating; and fishing while wading. Activities appro- <br /> <br /> <br />priate to a given river reach are selected to portray the impact of flow <br /> <br /> <br />~-. manipulation on that reach. <br />-.J <br />,,~, <br />..;;.. <br /> <br />E. Response Criteria <br /> <br />. <br /> <br />The methodo logy at thi s ti me re 1 i es upon the parameters of depth and <br />velocity and the response of fish species and recreational activities to <br />changes therein. Indications are that these two are the most significant <br />in measuring stream flow impacts. Other important parameters, however, <br />i ncl ude temperature, sediment and other stream pollutants. cover, and <br />substrate. These are considered by the biologist when interpreting the <br />findings resulting from application of the methodology, using such data <br />as may be available. Very recently, substrate characteristics have been <br />worked in as a factor in the simulation model. <br /> <br />F. Simulation Modeling Techniques <br /> <br />Distribution of depths and velocities throughout a representative reach <br /> <br /> <br />can be simulated for each month of the year using (1) pool/riffle ratio; <br /> <br /> <br />(2) bank-full width/depth ratio; (3) assumed cross-sectional form; (4) <br /> <br /> <br />median (or other levels of) monthly discharge; and (5) usual hydraulic <br /> <br /> <br />equations. The data needed for this simulation include: <br /> <br />1. Cross-section information for at least one typical pool and one <br /> <br /> <br />typical riffle; average length of pools and riffles; water surface <br /> <br />. <br /> <br />elevations and/or slope. <br /> <br />12 <br />