Breathing new life into legacy integrated surface groundwater models using gisbased adaptive mesh, hydrology refinement and data mapping tools
In a time of fiscal restraint and with environmental project funding in decline there is an increased interest in revisiting past modeling studies and improving upon legacy models rather than beginning the development process again from scratch. This trend coincides with a significant increase in the computing and analytical power of public domain and commercial GIS systems and the ability to tackle new problems through the availability of code to support customized applications. The paper describes GIS-based analytical tools developed to support the calibration and application of integrated groundwater and surface water modelsWESTSIMand C2VSIM (based on the IWFM code) and HydroGeoSphere (HGS) that rely on information from previous published USGS models, of which CVHM is the latest realization. These models are being used in water allocation planning by the US Bureau of Reclamation and California Department of Water Resources to simulate groundwater resource utilization, estimate the aquifer safe yield and to simulate potential subsidence impacts of over-stressing regional aquifers. California increasingly relies on its groundwater basins to supply municipal, industrial and agricultural water supply to 37 million people. Four tools are described. The first is an adaptive mesh refinement tool developed within ArcGIS as a means of improving the ability of a finite element mesh to represent salient watershed features such as streams, water district boundaries, well locations and geologic faults. The tool is highly interactive allowing new realizations of the mesh to be created on-the-fly so as to recognize important new watershed characteristics and recognize these features in the mesh. The second tool is a robot that develops a flow path on the landscape for surface water where no clear channel exists. The robot, developed within ArcGIS, queries surrounding raster cells, within a defined search radius, finding the most likely flow path and the natural drainage of the region based only on elevation data.The third a procedure to assign aquifercharacteristics from existing calibrated groundwater flow models to the appropriateWESTSIM, C2VSIM and HGS nodes using the same robotic scanning algorithm. The fourth a metadata organizational tool calledDataSpace for organizing GIS data files into an information framework that makes intuitive sense to theanalyst and helps to improve analyst productivity.