Structurally complex hydrogeologic regions are not simulated well with traditional (two-dimensional) digital geologic framework models such as ArcGIS.  EarthVision, a three-dimensional geographic information system (GIS), provides a platform to compile various sources of data from a complex aquifer system into a three-dimensional conceptual model that can be exported for use in MODFLOW or other groundwater flow modeling software.  A three-dimensional digital hydrogeologic framework model (DHFM) of the West Mogollon Mesa area of central Arizona was constructed using EarthVision. Data necessary for the completion of this model were accurate elevations for the tops of hydrogeologic units and locations and offset of faults. These data were determined using well logs and existing geologic maps which were field checked and then compiled into a database to be assembled into the DHFM.

Fossil Springs is the largest spring discharging in the West Mogollon Mesa area, at the base of the Mogollon Rim in the Transition Zone physiographic province. This province is characterized by steeply dipping normal faults with large offsets (up to 700 m) which can not be efficiently simulated using traditional two-dimensional GIS software. The aquifer system of the West Mogollon Mesa is a horizontal, stacked system, composed of two regionally extensive aquifers which are separated by a confining layer. A recently constructed hydrologic model for the Mogollon Highlands suggests that most regional flow originates in the shallowest aquifer by recharge along the Mogollon Rim and that recharge to the lower aquifer occurs as leakage from the above aquifer through faults and fractures. Fossil Springs discharges at the contact of two limestone units, at the top of the lower aquifer and intersection of two faults. Modeling this system in EarthVision allowed for a better understanding of the structural relationships and hydrologic processes of the region before a numerical flow model was constructed.