EFFECTIVENESS OF DIGITAL GEOLOGIC FRAMEWORK MODELS IN LARGE, DATA-POOR, REGIONAL GROUND WATER MODELS

The Coconino Plateau is the recharge area for the Redwall-Muav aquifer that feeds seeps and springs on the South Rim of the Grand Canyon. Few data are available for understanding structural and stratigraphic relationships within the subsurface of the Coconino Plateau. Digital geologic framework models were used to help construct a conceptual model of the geology of the Coconino Plateau, the 9600 km² area between Flagstaff and the Grand Canyon in northern Arizona. The digital geologic framework models were used as the conceptual framework for a three-dimensional ground water flow model. Previous work includes a digital geologic framework model created using a fully three-dimensional framework model, Stratamodel. For this study, digital geologic framework models using the two-dimensional ArcView and Surfer Geographical Information Systems (GIS) were created. The models were compared to each other based on three fundamental categories: input, analysis and output. The input category consists of the types, numbers and sizes of input files of raw spatial data that each software package is capable of accepting for analysis. The analysis category consists of the number and quality of methods (algorithms) used to interpolate geologically reasonable stratigraphic contact surfaces from a very scarce data set. The output category consists of display options and quality of output images for the purpose of presentation and communication of the spatial information. Stratamodel produces the highest quality geologic representation but also is very expensive. ArcView is capable of accomplishing the goals but is fairly expensive and has some problems with large files. Surfer is the least expensive but also is limited in it's capabilities to represent the geology of the region.