Water Resources Research Act Program

Details for Project ID 2006OR76B

Modeling Effects of Channel Complexity and Hyporheic Flow on Stream Temperatures

Institute: Oregon
Year Established: 2006 Start Date: 2006-02-15 End Date: 2007-02-14
Total Federal Funds: $20,194 Total Non-Federal Funds: $40,225

Principal Investigators: Scott Wells

Project Summary: Stream temperatures are affected by multiple forcing functions, including surface heat exchange (including solar radiation, evaporation, conduction, and net long wave radiation) and hyporheic flows. Each of these forcing functions is directly influenced by the level of channel complexity in the stream channel and riparian shading. Knowing that stream channel complexity has diminished over time in the Willamette basin, an important question to consider is what were stream temperatures before we altered the natural channels? This is an important issue in determining what natural conditions were and how we have strayed from these so-called natural conditions as a result of channelization, dam building, and changes to the riparian vegetation and deforestation. The current Oregon DEQ temperature TMDL relies on determining a natural condition. In order to develop an understanding of what that is, a hydrodynamic and water quality computer simulation model will be applied to the Willamette river with several levels of channel complexity and varying rates of hyporheic flows. Adapting the model used to develop total maximum daily loads (TMDL) for temperature in the Willamette River, the effects of present and past channel complexity on water temperatures will be determined. The model used to develop the TMDL was the Corps of Engineers dynamic 2-D model CE-QUAL-W2, which consists of directly coupled hydrodynamic and water quality transport models and simulates parameters such as temperature, algae concentration, dissolved oxygen concentration, pH, nutrient concentrations and residence time. The model also incorporates a dynamic shading algorithm for both vegetative and topographic shading on water bodies. A comparison of model results will indicate whether a more complex channel configuration will reduce stream temperatures provided streamside vegetation provides sufficient shade cover.