HR: 0800h
AN: H51C-1144    [Abstracts]
TI: Implications of Groundwater Dynamics on Long-Term Changes of River Basin Topography and Hydrologic Response, With Application to the WE-38 Basin, Pennsylvania
AU: * Huang, X
EM: xjhuang@psu.edu
AF: Pennsylvania State University, 212B Sackett Building, University Park, PA 16802 United States
AU: Niemann, J
EM: jniemann@engr.colostate.edu
AF: Colorado State University, A226 Engineering Building, Fort Collins, CO 80526 United States
AB: Numerous studies have examined the impacts of geomorphology on the hydrologic processes of river basins, but much less attention has been given to the opposite problem: the effects of hydrologic processes on the evolution of river basin topography. Fluvial erosion processes are driven by surface runoff and streamflow, which depend on precipitation rates, soil moisture dynamics, and groundwater flow. All of these processes help determine spatial and temporal patterns of runoff and streamflow in a basin. Horton runoff occurs where the infiltration capacity is exceeded by the rainfall intensity and might produce relatively uniform incision across a basin. Dunne runoff and groundwater discharge typically occur in areas adjacent to river channels, thus eroding river networks and their neighboring locations. Groundwater is expected to be especially important to patterns of erosion when the infiltration capacity is large enough to absorb significant precipitation. On the Colorado Plateau, for example, groundwater leaves significant geomorphic signatures such as amphitheater-shaped channel heads and near constant valley widths from source to outlet. In this analysis, we investigate the role that groundwater movement plays in long-term landscape evolution using a landscape evolution model that has been modified to include a more detailed representation of basin hydrology. In the model, precipitation is generated by a stochastic process that includes realistic inter-storm variation, and the precipitation is partitioned between surface runoff and groundwater recharge using specified infiltration and recharge rates. Groundwater flow is simulated by a two-dimensional Dupuit equation for a homogeneous, isotropic, unconfined aquifer with an irregular underlying impervious layer. The model is applied to the WE-38 basin, an experimental watershed in Pennsylvania. This site was selected as a study area because substantial hydrologic and geomorphic information is available including rainfall data, streamflow data, groundwater table elevations, and estimated parameters for the geomorphic processes. First, the hydrologic model is calibrated to match observed streamflow data, then the combined hydrologic/geomorphic model is used to investigate several hypothetical scenarios. The scenarios investigate the role of groundwater as the infiltration capacity, hydraulic conductivity, and impervious layer are modified. The resulting topographies are analyzed and their hydrologic behavior is characterized. The results indicate that groundwater plays an important role in shaping fluvial landscapes and thus affects the long-term evolution of hydrologic response, especially in basins with large infiltration capacities and thick aquifers.
DE: 1800 HYDROLOGY
DE: 1815 Erosion and sedimentation
DE: 1824 Geomorphology (1625)
DE: 1829 Groundwater hydrology
DE: 1854 Precipitation (3354)
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting