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4 <br />The intense competition for water and the growing recognition <br />that instream uses of water must be protected led to the development <br />of numerous methods for assessing instream flow needs. Most of these <br />methods focused on the protection of indigenous fish populations, <br />particularly salmonids, because of their recreational and commercial <br />importance. Some of the earliest studies to determine instream flow <br />needs were conducted below large hydroelectric facilities located on <br />coastal rivers of northern California (e.g., Curtis 1959, Delisle and <br />Eliason 1961, review by Fraser 1972a). After legislation that <br />recognized the importance of maintaining suitable stream flows had <br />been passed in Oregon, field studies were initiated in 1961 to <br />determine specific flow requirements of salmonids at different times <br />of the year (Sams and Pearson 1963, Thompson 1972). In 1962, the U.S. <br />Forest Service developed a transect line, cluster sampling procedure <br />for use on trout streams in Utah and Idaho (Dunham 1972). A few years <br />later, work on the now well-known Tennant or Montana Method (Elser w <br />1972, Tennant 1976) was initiated in Montana. <br />Beginning in the early 1970's, several workshops were held in the <br />Northwest to discuss the various methods that had been developed. As <br />a result of this communication, methods were compared and modified to <br />incorporate the new information that was being collected on the <br />habitat requirements of salmonids. Several reviews of the methods <br />available for assessing instream flow needs were also published during <br />this period (Fraser 1972a, Giger 1973, Hooper 1973). <br />At the same time that methods were being developed 'to assess the <br />instream flow needs of fish species, site-specific 'studies were <br />conducted to examine the biological consequences of stream flow <br />regulation. Results of these studies showed that the primary impact <br />of reduced flows on fishes was a reduction in usable habitat (Holden <br />1979). A trans-basin diversion project on the Trinity River in <br />northern California, for example, resulted in a significant reduction <br />in salmonid spawning habitat below the point of diversion (Smith <br />1976).