INCORPORATING PROFESSIONAL JUDGMENT INTO GROUNDWATER CONTOURING TOOLS WITHIN ARCGIS

Automated contouring methods applied to sparse water table elevation data often frustrate geologists with unrealistic results that poorly reflect the geologist's interpretation. Common interpolation methods implemented in Geographic Information System (GIS) software, like linear interpolation with triangular irregular networks (TINs), inverse distance weighting, and spline fitting, rigidly apply mathematical formulae based on the geographic location of the input points. The output of algorithms usually fails to meet expectations because the input excludes additional knowledge of the water table inferred from local topographic trends, surface water bodies, and other hydrogeologic features. Also, the resulting contours may not conform to the artistic license a geologist may use to account for such features. Geologists using GIS may digitize slope break lines and control points with estimated values associated with these features and include them with field data in attempts to guide the algorithm to a better solution. However, the iterative process of adding and adjusting control points exasperates novice users and frequently fails to substantially outperform manual drafting by experienced professionals, particularly with sparse data. This study sought to develop an interactive tool to incorporate professional judgment into automated contouring and lessen the learning curve of creating contours that account for hydrogeologic features for novice GIS users. The tool leverages the extensibility of Esri's ArcGIS Desktop software, building upon a robust suite of mapping tools. The interface gives the user tools to create contours modified and stylized to reflect common hydrogeologic features, such as a gaining stream causing contours to "V" upstream. The tool is designed to allow users to achieve more conventional contour patterns in less time than plug-and-chug control point methods.