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TECHNICAL SUPPORT FOR NONPOINT SOURCE POLLUTION STUDIES |
Client:
Tetra Tech, Inc., Fairfax, VA
Funding:
U.S. EPA Office of Science and Technology, Washington, DC
As a subcontractor to Tetra Tech, Inc., AQUA TERRA Consultants provided technical support to EPA Office of Water/Office of Science and Technology and the EPA Office of Research and Development's Environmental Research Laboratory in Athens, Georgia in the form of model evaluation and model application assistance for the Upper Grande Ronde Temperature TMDL study in Eastern Oregon.
The loss of riparian vegetation due to grazing practices and channel modifications has been identified as a major factor leading to increased water temperature and loss of habitat, both of which have negatively affected the salmon and steelhead populations within the Upper Grande Ronde. Under the auspices of developing a TMDL for the river, AQUA TERRA modified and applied the Hydrologic Simulation Program-FORTRAN (HSPF) in an innovative approach to evaluating the effects of riparian vegetation on stream water temperatures.
To simulate stream temperatures on a watershed scale, shading dynamics of topography and riparian vegetation were computed to estimate the amount of solar radiation that is actually adsorbed by water within each stream reach. To support this effort, EPA implemented a series of computational procedures in the form of a computer program named SHADE; the procedures identify the geometric relationships among the sun position, stream location and orientation, and riparian shading characteristics. The SHADE-generated solar radiation estimates were used as input to perform a HSPF simulation of hourly stream temperatures. In addition, a methodology for computing the heat flux between water and streambed was selected, evaluated, and implemented in the HSPF code.
AQUA TERRA provided guidance and review of HSPF application procedures, and specialized algorithms (i.e. the SHADE program) to account for diurnal stream shading affects on the water temperature regime of the stream channel.