A GIS approach to integrating the results of surface and groundwater models: application to south fork of the Kern River

Abstract

Geographic Information Systems (GIS) is a useful tool in integrating surface and groundwater models for a variety of applications. Typically, a modeler will run either a surface or groundwater model to analyze a study area, but not both. At the South Fork Kern River, which contains California's longest continuous riparian system, many endangered species rely on a delicate balance between surface and groundwater. The Willow Flycatcher, for example, is an endangered bird species that requires pools of surface water and specific cottonwood canopy conditions for its survival. The South Fork Kem surface water model was developed using the Hydrologic Engineering Center (HEC) models HEC-HMS and HEC-RAS. Analysis of these models will result in a GIS coverage displaying the floodplain extent and surface water depths for a given scenario. The groundwater model was run using MODFLOW and the new Riparian Evapotranspiration Package (RIP-ET) by Maddock and Baird, 2002. This new package provides a better estimate of ET, and therefore more accurate inputs to a groundwater model than the traditional ET package. A pre- and post-processor (RIPGIS) was written as a custom application within Arc View GIS to guide modelers through the analysis of inputs and outputs to RIP-ET. The surface and groundwater models were then integrated through GIS to help identify areas of stressed riparian habitats. This model integration can help assess not only the current state of riparian health, but also future development impacts.