Analytic-element modeling of supraregional groundwater flow: Concepts and tools for automated model configuration

The analytic-element method (AEM) is an appealing technique for modeling steady-state groundwater flow at the supraregional scale (defined here as >10,000 km²) because the computational demand is determined primarily by the number of modeled hydrologic features and not constrained by the size of the domain. In this paper, we introduce AEM to practitioners unfamiliar with the approach and present modeling concepts and new tools designed to facilitate the automated processing of AEM models containing thousands of hydrologic features. Topics include assignment of element types for surface water features, automated simplification of lines and polygons, conversion of polygonal elements to less computationally demanding circles and ellipses, iterative solution algorithms for models that include nonlinear resistance elements, software implementation, and integration of AEM simulators with calibration utilities and GIS. Software implementation of the concepts and tools is discussed and demonstrated for a case study of Wisconsin's Northern Highland Lakes region.