HR: 0800h
AN: H21F-1089 INVITED     [Abstracts]
TI: Geologically Mediated Groundwater Storage can be a First-Order Control on Streamflow Response to Changing Climate
AU: * Grant, G E
EM: gordon.grant@oregonstate.edu
AF: USDA Forest Service, Pacific Northwest Research Station, 3200 Jefferson Way, Corvallis, OR 97331 United States
AU: Tague, C
EM: ctague@mail.sdsu.edu
AF: Dept. of Geography, San Diego State University, San Diego, CA 92182-4493 United States
AU: Jefferson, A
EM: anne.jefferson@oregonstate.edu
AF: Dept. of Geosciences, Oregon State University, Corvallis, OR 97331 United States
AB: Previous research has revealed that spatial patterns of summer streamflow in the Cascade Mountains of Oregon vary dramatically between the geologically distinct High and Western Cascade regions. A key control on streamflow response between these two regions is the partitioning of water input between a fast-draining shallow subsurface flow network (Western Cascades) versus a slow-draining deeper groundwater system (High Cascades). These differences result from extremely high contrasts in rock permeability and porosity and drainage density between landscapes dominated by young versus old volcanic rocks. We consider how geologically-based differences in groundwater storage capacity can significantly alter streamflow response to climatic warming. In particular, we expect that for the young volcanic terrains comprising the High Cascade Range of Oregon and Northern California, ground water storage is of sufficient magnitude to buffer potential changes in snowpack volume, hence summer streamflow, due to changing climate. Older volcanic and granitic landscapes in the Oregon Western Cascades and California Sierras, in contrast, will be much more sensitive to diminished snowpacks and summer streamflow changes. Even within the Sierras, local variations in bedrock geology and associated differences in volume and seasonal fluxes of subsurface water will likely result in significant spatial variability in sensitivity to climate forcing. Taken together, these results imply that current models linking climate and streamflow changes need to account for differences in groundwater storage as a first-order control.
UR: http://www.fsl.orst.edu/wpg
DE: 1829 Groundwater hydrology
DE: 1833 Hydroclimatology
DE: 1860 Runoff and streamflow
DE: 1620 Climate dynamics (3309)
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting