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<br />keyword Sedimentation that contain extensive <br />bibliographies on th~s subject. <br /> <br />Water Temperature <br /> <br />Aquatic organisms are poikilothermic <br />animals in which the temperature of their <br />environments governs their physiological <br />processes and behavior (Hoar and Randall <br />1969, 1970; Sylvester 1972). Migratory <br />behavior, reFroductive cycles, and feeding, <br />as well as many other functions, are re- <br />lated to water temperature in such animals. <br />All species exhibit preferences to water <br />temperatures and each has an optimum tem- <br />perature for matabolism and activity. Water <br />temperatures that are lower or higher than <br />optimum usually are accompanied by less <br />activity in aquatic organisms. Any man- <br />made alteration to an aquatic habitat that <br />alters temperature will affect the organisms <br />that are found there. <br /> <br />Brown (1970) provided a technique for <br />predicting the effect clearcutting on <br />stream temperature and stated that "the <br />temperature change that occurs between two <br />points on a stream is directly proportional <br />to the surface area of the stream an~ the <br />heat load applied between these points". <br />Therefore. removal of the forest canopy <br />would allow a larger area of the stream to <br />be exposed to solar radiation and would <br />result in increased water temperature if <br />the flow does not change. Less change <br />would occur during increased flow and a <br />greater change in temperature would occur <br />at lower flows. Strip mining would cause <br />similar effects on the water temperature <br />of streams. <br /> <br />Geen (1974) reported that it is impos- <br />sible to predict the location of the ther- <br />mocline in newly constructed reservoirs <br />and, therefore, it is difficult to deter- <br />mine the proper location for penstocks. <br />The Bureau of Reclamation (1975) proposed <br />modifications in the penstocks of Flaming <br />Gorge Dam on the Green River, Utah-I'lyoming, <br />that would increase water temperatures be- <br />low the dam and increase the growth of <br />rainbow trout. Changes in the fish species <br />composition below dams as a result of <br />modifying water temperature were reported <br />by Spence and Hines (1971b), Mullan et al. <br />(1976), and Symons et a!. (1964). Similar <br />changes in the species composition of in- <br />vertebrates were related to alterations in <br />the natural temperature regime of a stream <br />(Spence and Hines 1971b; Pearson and Frank- <br />lin 1968; Ward 1976). <br /> <br />Increased thermal effluents into aqua- <br />tic environments have resulted from greater <br />demands for electric power and growth of <br />the electric power industry. The possible <br />effects of thermal effluents on fish were <br />reviewed by Sylvester (1972) who reported <br />that metabolism, reproduction and develop- <br />ment, and behavior of fish are affected <br />largely by water temperatures. He also <br />pointed out that the toxicity of pollutants <br /> <br />may be intensified with increasing tempera- <br />ture and that fish may be more susceptible <br />to diseases with increasing temperatures. <br />The predation rate of juvenile fish that <br />have been exposed to thermal shock may in- <br />crease with the severity of the shock since <br />such fish are not as able to avoid predators <br />and their altered behavior provides a search <br />image for the predator. Thermal effluents <br />may be useful in aquaculture if given proper <br />consideration to the engineering and econo- <br />mical aspects in design of plants (Yee 1973). <br /> <br />The entrapment and impingement of fish <br />by power plant cooling-water intakes has <br />gained attention and has been reviewed by <br />Hanson et al. (1977). A bibliography on <br />fish protection at water diversions and in- <br />takes was published by Sharma (1973). Dam- <br />aged to fish from impingement or entrapment <br />on water intakes depends upon the fish spe- <br />cies, life stage, and size. Fish may die <br />immediately if extensive physical damage <br />is done during the impingement on the water <br />intake or delayed mortality may result from <br />physiological damage or stress (Hanson et <br />al. 1977). Engineering considerations in <br />intake location and design may help to solve <br />some of the problems that have occurred at <br />water intakes. <br /> <br />The water temperatures of trout streams <br />in Southwestern Wisconsin were reduced by <br />shortening the stream channels (Stoeckler <br />and Voskuil 1959). This is an example of <br />using stream channelization to benefit fish <br />populations. The advantages as well as the <br />limitations of changes in water temperature <br />should be considered before alterations of <br />aquatic enviro~~ents are made. Without <br />these considerations during the planning <br />states of a project, it may not be possible <br />to change water temperatures without ex- <br />pensive modifications in engineering design <br />or before a unique fish population may be <br />destroyed. <br /> <br />Riparian Vegetation <br /> <br />The importance of cover to trout popu- <br />lations in streams has been recognized by <br />numerous biologists (e.g., Boussu 1954; <br />Giger 1973; Gunderson 1968; Hooper 1973; <br />Lorz 1974). Riparian vegetation provides <br />shade that serves as cover for fish and <br />also prevents large fluctuations in water <br />temperatures. Overhanging vegetation and <br />the roots of trees serve as habitat for <br />stream-swelling fish. The logs and branch- <br />es of dead trees that fall into streams <br />also serve as habitat for some species of <br />fish. The organic detritus from leaves <br />adds a source of nutrients to the stream <br />ecosystem and terrestrial insects that <br />fall into the stream provide a large propor- <br />tion of the food for fish at certain times <br />of the year. <br /> <br />Vegetation is very important to the <br />hydrology of a forested watershed. It <br />regulates the flow of water so that the <br />peak runoff conditions are minimized, and <br /> <br />67 <br />