HYDROGEOLOGICAL DATA ASSIMILATION FOR A 3D INTEGRATED SURFACE-SUBSURFACE MODEL OF THE CHESAPEAKE BAY WATERSHED

Accurate representation of hydrogeological properties is one of the most important tasks in developing subsurface flow models. For large scale applications, the necessary integration of scarce or scattered data from varied sources becomes even more of a challenge. As a part of the development of a highly resolved 3D integrated hydrologic model of the Chesapeake Bay Watershed, we have developed a conceptual hydrogeological model of the study domain. The model domain encompasses an area of 400,000 sq. km within the states of New York, Pennsylvania, Delaware, Maryland, Virginia, and West Virginia and traverses five physiographic provinces. We have constructed a relational database in combination with GIS, geologic modeling and geostatistical tools to compile, analyze, aggregate and visualize the data. The database combines information on aquifers dimensions and their hydraulic properties including storage coefficients, porosity, and hydraulic conductivity. Aquifer characteristics and hydraulic properties have been retrieved from existing hydrogeological studies including aquifer tests and groundwater modeling studies within the region, geologic maps, and investigation of drillers’ logs, and well test data. Well log information has been collected from four state environmental agencies and analyzed to derive hydraulic conductivity values from specific capacity. The database is constructed in the Microsoft Access environment. Subsurface properties and well locations are georeferenced in ESRI Arcmap. A geologic model platform, Rockworks ^TM, is used to further visualize and present the subsurface data in 3D form. The conceptual model is developed in a comprehensive data assimilation framework that can be easily managed and used as input to hydrologic models and can also be shared with different entities.