HR: 1340h
AN: H13B-1333    [Abstracts]
TI: Application of a process-based, basin-scale stream temperature model to cumulative watershed effects issues: limitations of Forest Practice Rules
AU: * Allen, D M
EM: allen@eps.berkeley.edu
AF: Department of Earth and Planetary Science, U.C. Berkeley, McCone Hall 3rd Floor, Berkeley, CA 94720 United States
AU: * Allen, D M
EM: allen@eps.berkeley.edu
AF: Stillwater Sciences, 2855 Telegraph Avenue, Ste. 400, Berkeley, CA 94705 United States
AU: Dietrich, W E
EM: bill@eps.berkeley.edu
AF: Department of Earth and Planetary Science, U.C. Berkeley, McCone Hall 3rd Floor, Berkeley, CA 94720 United States
AB: Elevated stream temperatures increase the metabolic demands on fish, and at sufficiently high levels, can be lethal. Timber harvesting increases stream temperature by removing dense riparian canopy and exposing the channel to direct shortwave radiation. We have developed a simple, process-based stream temperature model, BasinTemp, which predicts water temperatures for very short reaches for entire channel networks. Spatially explicit radiation predictions are generated in a GIS, while heat and mass transfer processes are modeled using a simple 1D steady-state energy balance model. The model assumes that direct shortwave radiation is the primary control on water temperatures during summer months and that topography and most importantly, riparian vegetation, moderate the amount of direct solar radiation received at the stream surface. An optimization routine uses measured thermograph data from the basin of interest to improve model predictions. This feature eliminates the need for substantial site-specific field data to calibrate the model. The model has been tested on several basins in Northern California and Southern Oregon. Model performance has generally be excellent. For example, an application to Bull Creek, a 110km² basin in the South Fork Eel River basin in Northern California, generated an RMSE of 0.25 degrees C and an R² of 0.99 for observed versus predicted temperatures. An important feature incorporated into the model is the capability to adjust riparian tree heights and to examine the resulting local and downstream cumulative temperature effects. We show results where we alter riparian vegetation through a range of plausible shade scenarios on low order, headwater channels. These channels, which comprise most of the stream network, typically receive little if any protection from state Forest Practice Rules. Using a channel slope-based classification system appropriate for freshwater coho salmon lifestages, we demonstrate that available habitat downstream in the basin is strongly dependent on the amount of riparian shade protection provided to upstream channels.
DE: 1860 Streamflow
DE: 1871 Surface water quality
DE: 1878 Water/energy interactions (0495)
SC: Hydrology [H]
MN: Fall Meeting 2005