HR: 10:50h
AN: H11H-03    [PDF]
TI: Development of a Coupled Land Surface and Ground Water Model for use in Watershed Management
AU: * Maxwell, R M
EM: maxwell15@llnl.gov
AF: Environmental Sciences Division, Larence Livermore National Laboratory, 7000 East Avenue, Livermore, CA 94550 United States
AU: Miller, N L
EM: nlmiller@lbl.gov
AF: Earth Sciences Division, Lawrence Berkeley National Laboratory, One Cyclotron Road, Berkeley, CA 94720 United States
AB: Management of surface water quality is often complicated by interactions between surface water and groundwater. Traditional Land-Surface Models (LSM) used for numerical weather prediction, climate projection, and as inputs to water management decision support systems, do not treat the lower boundary in a fully process-based fashion. LSMs have evolved from a leaky bucket to more sophisticated land surface water and energy budgets that typically have a so-called basement term to depict the bottom model layer exchange with deeper aquifers. Nevertheless, the LSM lower boundary is often assumed zero flux or the soil moisture content is set to a constant value; an approach that while mass conservative, ignores processes that can alter surface fluxes, runoff, and water quantity and quality. Conversely, models for saturated and unsaturated water flow, while addressing important features such as subsurface heterogeneity and three-dimensional flow, often have overly simplified upper boundary conditions that ignore soil heating, runoff, snow and root-zone uptake. In the present study, a state-of-the-art LSM (CLM2.0) and a variably-saturated groundwater model (ParFlow) have been coupled as a single column model. An initial set of simulations based on data from the Project for Intercomparison of Land-surface Parameterization Schemes (PILPS) and synthetic data demonstrate the temporal dynamics of both of the coupled models. Changes in soil moisture and movement of the water table are used as indicators of conservation of mass between the two models. Sensitivity studies demonstrate the affect of precipitation, evapotransporation, radiation, subsurface geology and heterogeneity on predicted watershed flow. The coupled model will ultimately be used to assist in the development of Total Maximum Daily Loads (TMDLs - a surface water quality standard) for a number of pollutants in an urban watershed in Southern California in the United States. Sensitivity studies demonstrating the effects of watershed flow in uncoupled and coupled modes will be presented.
DE: 1829 Groundwater hydrology
DE: 1831 Groundwater quality
DE: 1866 Soil moisture
DE: 1871 Surface water quality
DE: 1878 Water/energy interactions
SC: Hydrology [H]
MN: 2003 Fall Meeting