HR: 0800h
AN: H21F-1090    [Abstracts]
TI: Predicting Contrasting Responses to a Warmer Climate for Groundwater and Shallow Subsurface Dominated Systems in the Oregon Cascades
AU: * Tague, C L
EM: ctague@mail.sdsu.edu
AF: San Diego State University Department of Geography, 5500 Campanile Drive , San Diego, CA 92182
AU: Farrell, M J
EM: mfarrell@rohan.sdsu.edu
AF: San Diego State University Department of Geography, 5500 Campanile Drive , San Diego, CA 92182
AU: Grant, G
EM: Gordon.Grant@oregonstate.edu
AF: USDA Forest Service, Pacific Northwest Research Station, 333 SW First Avenue , Portland, OR 97204
AU: Jefferson, A
EM: jeffersa@geo.orst.edu
AF: Oregon State University Department of Geosciences, 104 Wilkinson Hall, Corvallis, OR 97331
AU: Choate, J
EM: jchoate@rohan.sdsu.edu
AF: San Diego State University Department of Geography, 5500 Campanile Drive , San Diego, CA 92182
AB: Recent studies predict that projected climate change will lead to significant reductions in summer streamflow in the mountainous regions of the Western US. Hydrologic modeling applications directed at quantifying these potential changes have focused on the magnitude and timing of spring snowmelt as the key control on changes in streamflow regimes. In this study we use a process based, hydrologic modeling approach to explore the importance of geology as a regional scale control on summer streamflow sensitivity to climate variability. In the Oregon Cascades, our previous empirical analysis of streamflow patterns indicates strong spatial differences in summer streamflow behaviour between the High and Western Cascade geologic provinces. While differences in climate forcing contribute to the distinct flow regimes of the High and Western Cascades, our empirical analysis suggests that geologic based flowpath differences are the dominant control. We hypothesize that the prevalence of deeper groundwater spring systems in the High Cascades maintains higher and more consistent summer streamflow volumes relative to those of the shallow subsurface dominated Western Cascades. In this current research, we use a spatially distributed, process-based hydro-ecological model, RHESSys, to explore the relative roles played by climate and geologic-based difference in flowpaths in creating the distinct summer streamflow signatures of the High and Western Cascades. RHESSys is applied to two case-study watersheds of similar elevation and drainage area, Lookout Creek in the Western Cascades and Clear Lake in the High Cascades. A Monte-Carlo based hydrologic calibration is used to quantify difference in geologic based drainage efficiency between the two watersheds. Simulation scenarios using a range of climate forcing data are used to explore differences in the sensitivity of High Cascade and Western Cascade watersheds to predicted climate change. Results indicate that the groundwater system of the High Cascade site is likely to buffer the impact of increasing temperature and associated changes in snow accumulation and melt. Simulation results for the Western Cascade site, on the other hand, show responses similar to those predicted by previous larger scale hydrologic modeling efforts. These results illustrate the importance of groundwater flow mechanisms as a key control on climate change sensitivity in Oregon. We discuss future modeling efforts designed to extend this analysis to explore the impact of different groundwater flow mechanisms in the Sierras and to investigate the role of vegetation dynamics as a secondary control on summer flow regime sensitivity to climatic change.
DE: 1800 HYDROLOGY
DE: 1829 Groundwater hydrology
DE: 1860 Runoff and streamflow
DE: 1866 Soil moisture
DE: 1600 GLOBAL CHANGE (New category)
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting