HR: 14:10h
AN: H23J-03    [Abstracts]
TI: Modeling Streambed Heating in Shallow Streams
AU: * Annear, R L
EM: annearr@cecs.pdx.edu
AF: Portland State University, Department of Civil and Environmental Engineering PO Box 751, Portland, OR 97207-0751, United States
AB: The Oregon Department of Environmental Quality, USA is developing Total Maximum Daily Loads to address water quality concerns and threatened and endangered species habitat requirements. Approximately 940 water body segments are listed as water quality limited for temperature in Oregon. CE-QUAL-W2 Version 3 is a two- dimensional water quality and hydrodynamic model capable of modeling rivers, reservoirs and estuaries. An important aspect of modeling stream temperature is handling the short-wave solar radiation that penetrates the water surface and impacts the streambed, which can affect water temperatures under low-flow conditions. The Bull Run River-Reservoir system in Oregon is a 264 km2 watershed 42 km east of downtown Portland and serves as the city's primary drinking water source. A dynamic, three-dimensional streambed heat transfer model was developed and calibrated with field data from the Lower Bull Run River and laboratory experiment data. Model results compared well to field data from bedrock and cobble substrates. The model calibration for the cobble substrate revealed the substrate interstitial water temperature played a large role in the substrate temperatures and was necessary to calibrate the model. The streambed heating model compared well with the laboratory experiments' data in many cases. The model was compared to two analytical models and a one- dimensional model for various application cases and performed well. The streambed heating model was implemented in CE-QUAL-W2 and a sensitivity analysis examined the impacts of river flows, substrate type and streamside shading. Water temperature impacts focused on daily minimum and maximum temperatures. Increased flow rates resulted in decreased water temperature impacts from streambed heating. The largest water temperature impacts occurred with the bedrock streambed with decreasing impacts once cobble was incorporated. Increased streamside shading reduced the impact of streambed heating. General guidelines were discussed when streambed heating may be an important part of the surface water heat budget.
DE: 0496 Water quality
DE: 1814 Energy budgets
DE: 1847 Modeling
DE: 1871 Surface water quality
DE: 1878 Water/energy interactions (0495)
SC: Hydrology [H]
MN: 2007 Fall Meeting