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• <br />Introduction <br />The Instream Flow and Aquatic Systems Group (IF&ASG), in <br />cooperation with the U.S. Soil Conservation Service (SCS) and the <br />U.S. Fish and Wildlife Service (FWS), has developed a stream <br />network temperature model to predict instream water temperatures <br />based on historical or synthetic hydrologic, meteorologic, and <br />stream geometry conditions. The model is applicable to any size <br />watershed or river basin with a stream network of any stream <br />order and complexity. The model incorporates several features, <br />including: <br />- A heat transport model that predicts the average mean <br />daily water temperature and diurnal fluctuation in water <br />temperature as a function of stream distance. <br />- A heat flux model that predicts the energy balance between <br />water and its surrounding environment. <br />A solar model that predicts the solar radiation that <br />penetrates the water as a function of latitude, time of <br />year, and meteorological conditions. <br />A shade model that predicts the solar radiation-weighted <br />• shading from both topography and riparian <br />vegetation. <br />- Meteorological corrections that predicts air temperature, <br />relative humidity, and atmospheric pressure as a function <br />changes in elevation and latitude. <br />- Regression aids that smooth or fill in missing water <br />temperatures and discharges at headwater and other <br />internal locations. <br />Theurer (in press) has described the stream network temperature <br />model applications, theory, solution techniques, and computer <br />program documentation. The model predicts mean daily (24-hour <br />average) minimum night-time and maximum daytime water <br />temperatures. Additional model validation and applications have <br />been described by Theurer, et. al. (1982), Theurer and Voos <br />(1982), and Theurer (1983). <br />0