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<br />6 <br /> <br />" <br /> <br />Probability Curves <br /> <br />Probability curves are used to compute the effect of changes in these <br />critical parameters on each of the fish life stages and river-oriented <br />recreational uses. <br /> <br />. <br /> <br />Changes in stream conditions may cause the loss of a target species, <br />even though the conditions may not reach lethal levels. As both juven- <br />ile and adult fish are mobile, they may leave the altered zone or stream <br />before the conditions become lethal. For example, if an energy develop- <br />ment results in the introduction of significant amounts of heat, the <br />adults and juveniles may move to cooler zones in the same watercourse <br />or to different streams in a connected river system. The curves are <br />used to assess the possible changes in fish populations in each of the <br />representative stream reaches in a given Riverine Analysis Area. <br /> <br />In a similar manner, the changes in the recreation potential in the repre- <br />sentative stream reaches are evaluated. Changes in stream flow wi II <br />affect various recreation activities differently. Probability curves have <br />been established for most of the major instream recreation activities, <br />and the impact 'on each is computed separately. For instance, a <br />decrease in flow of a stream may adversely affect white water boating <br />but may make the stream more desirable for swimming. <br /> <br />PROCEDURES AND ANALYSES NECESSARY FOR INSTREAM <br />FLOW PORTION OF SECTION 13(a) ASSESSMENTS <br /> <br />STEPS IN RECONNAISSANCE METHODOLOGY FOR INSTREAM FLOW <br />ANALYSIS OUTLINED <br /> <br />. <br /> <br />This section of the report desc:-ibes in narrative format the steps includ- <br />ed in the reconnaissance flow methodology. These steps are as follows. <br /> <br />1. EstabliSh the Riverine Analysis Area(s) to be analyzed. <br /> <br />a. Water Resources Council regions involved. <br />b. RAA's within each WRC region. <br /> <br />2. Stratify and "sample" representative stream reaches within <br />each RAA; <br /> <br />a. From maps, locate USGS gaging stations and additional <br />stations as appropriate. <br />b. Stratify all streams into four to six size classes consider- <br />ing; (1) streams with entire length falling within the <br />RAA; (2) streams crossing the RAA; (3) streams flowing <br />into the RAA; and (4) streams originating in the RAA <br />but flowing into other RAA's. <br />c. "Select" one candidate stream to provide the initial data <br />for each stratified class, <br /> <br />. <br />