Conceptualization, characterization and numerical modeling of the Jackson Hole alluvial aquifer using ARC/INFO and MODFLOW

Abstract

Jackson Hole, a rapidly developing region of northwest Wyoming, is experiencing increased surface and groundwater related disputes. Currently, no basin-encompassing model to assess ground-water resources of the shallow ground-water system has been satisfactorily completed. The purpose of this study was to conceptualize and characterize the Jackson Hole hydrologic system using a procedure advocated by Kolm (1993), the ARC/INFO Geographic Information System (GIS) for data management and analysis, and MODFLOW (McDonald and Harbaugh, 1988), a finite-difference numerical model. The study area encompassed the Jackson Hole valley from Jackson Lake south to the Grand Canyon of the Snake River, Teton County, Wyoming. Published data, collected in disparate formats and scales, were integrated into an ARC/INFO database that included geographic, geologic and hydrologic data. Each data set was analyzed in ARC/INFO to characterize surface and subsurface conditions and the hydrologic system. A water table map was developed from well, river, natural lake, spring, vegetation and topography information. The flow system, conceptualized as three inter-connected systems, was estimated from the water table distribution, landforms, surface water features, and/or geology (depositional patterns, faulting). Conceptual models were numerically tested by interfacing the ARC/INFO database with MODFLOW. Mass balance estimates and a water table were predicted by MODFLOW for the shallow hydrologic system. The MODFLOW model was calibrated to estimates of recharge, discharge, baseflow and the water table map. A state-of-the-art database of the Jackson Hole hydrologic system was developed. The hydrologic system was characterized to the full potential of the available data. A basin-encompassing conceptual and numerical model, which simulates the hydrologic system in Jackson Hole, was satisfactorily completed. GIS technology was proven to be a viable technique for supporting the hydrologic investigation and the modeling process. Since the numerical model was not designed for ground-water management purposes, the development of a more complex, numerical model for management decisions, and additional data gathering are recommended.