A COUPLED SURFACE – SUBSURFACE HYDROLOGY MODEL BASED ON TRIANGULATED IRREGULAR NETWORKS: DISTRIBUTED SIMULATIONS IN REGIONAL WATERSHEDS

Hydrologists have long recognized the critical role played by the interaction of surface water and groundwater on the basin water balance and rainfall-runoff dynamics. Our understanding of the interaction between surface water and groundwater is aided through numerical models that best represent our current knowledge of the physical processes occurring in basins. The aim of this talk is to introduce a modeling framework for studying land-surface and subsurface hydrologic response to meteorological forcing. The TIN-based Real-time Integrated Basin Simulator (tRIBS) model has several distinguishing features that will be highlighted: (1) coupled unsaturated and saturated zones through a dynamic water table, (2) coupled energy and hydrologic balance at the land surface and (3) topographically-driven soil moisture redistribution, radiation and evapotranspiration. Accurate terrain representation with minimal computational expense is achieved through the use of a triangulated irregular network (TIN) terrain model. The tRIBS model has been used to simulate the spatial distribution of watershed hydrology in various basins by integrating spatial data on topography, land-surface properties and precipitation obtained from remote sensing. We will highlight results from multi-year flood simulations in regional basins, flood forecasting with radar rainfall data, sensitivity studies on terrain resolution and process studies on the effect of surface and groundwater coupling on basin response. By linking surface and groundwater modeling, the tool provides a complete description of the spatio-temporal variability and organization of the underlying hydrologic processes (e.g., infiltration, runoff, recharge, evapotranspiration, groundwater flow). These model capabilities allow the investigation of theoretical questions and practical problems in hydrologic science and water resources engineering.