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2 <br />associated with many of these uses. For example, mathematical <br />modeling has been an important component in determining instream flow <br />needs related to water quality (e.g., Mar 1973 and 1975 as cited in <br />Wyoming Water Resources Research Institute 1978a; Grenney et al. 1976; <br />Grenney and Porcella 1976; Porcella and Grenney 1976). Methods have <br />also been. developed to assess instream flow needs for recreation <br />(Andrews and Madsen 1976; Andrews et al. 1976; Morris 1976; Cortell <br />and Associates, Inc. 1977a,b; Hyra 1978; Wyoming Water Resources <br />Research Institute 1978a) and aesthetics (Andrews and Madsen 1976 <br />Masteller et al, 1976; Mittman 1976; Wyoming Water Resources Research <br />Institute 1978a). The effects of water level changes on riparian and <br />wetland communities have been described (e.g., Teskey and Hinckley <br />1977), and methods for assessing the effects of water management <br />practices upon riparian vegetation and wildlife are available (Kadlec <br />1976a,b; Wyoming Water Resources Research Institute 1978b). <br />Assessment of the instream flow needs of aquatic biota-, however, <br />has been the most difficult and controversial aspect of the instream <br />flow issue and is the subject of this report. Numerous methods have <br />been developed to assess the effects of flow regulation on aquatic <br />biota and to provide a basis for the determination of a suitable <br />stream flow recommendation. Although all components of lotic <br />ecosystems are affected by flow regulation (Sect. 1.1.1), the <br />assessment of instream flow needs of aquatic biota has focused <br />primarily on fish species. Only recently have studies of benthic <br />macro invertebrates been initiated, and these were limited to (1) <br />development of new techniques for assessing instream flow requirements <br />(Gore 1978, Railsback 1981), and (2) compilation and evaluation of <br />habitat suitability data from existing literature (Herricks and <br />Furnish 1980). <br />Because no consensus has been reached on the site-specific <br />applicability of these methods, especially in the eastern United <br />States, developers of small hydroelectric projects, which, depending <br />upon their design and operation, can alter the natural flow regime