Baltimore Ecosystem Study Institute of Ecosystem Studies

2011 BES Annual Meeting Presentation and Poster Abstracts

Integrated hydrologic modeling: discretization, initialization and hydrogeologic data input
Seck, Alimatou
Co-Authors: Alimatou Seck, Claire Welty, Joshua N. Cole, Reed M. Maxwell

Abstract: To investigate groundwater fluxes and flow paths within the Chesapeake Bay Watershed (CBW) and its interaction with surface flow, we have developed a highly resolved, 3D integrated hydrologic model of the region. As a part of this modeling project, efforts have been geared towards defining a suitable spatial discretization, developing an initialization strategy and gathering hydrogeologic input. We have populated a conceptual hydrogeological model of the study domain with available hydrogeologic data. We have created a hydrogeologic database using geologic maps, soils datasets, existing regional hydrogeologic literature and well test data. Here we present first the various datasets and their organization in a relational database. Secondly we present a spatial discretization study of the Monocacy watershed, a 5600 sq. km situated within the CBW domain. Models with homogeneous subsurface and topographically-derived slopes were evaluated at 500-m, 1000-m, 2000-m, and 4000-m grid resolutions. We used several options for water table depths and two rainfall forcing methods including (1) a synthetic rainfall-recession cycle corresponding to the regionís average annual rainfall rate, and (2) an initial shut-off of rainfall forcing followed by a rainfall-recession cycling. Results show the dominance of groundwater generated runoff during a first phase of the simulation followed by a convergence towards more balanced runoff generation mechanisms. We observe that the influence of groundwater runoff increases in dissected relief areas characterized by high slope magnitudes. As a result, in the domain conditions for this study, an initial shut-off of rainfall forcing proved to be the more efficient initialization method. This approach is also being implemented in an integrated model of the Gunpowder-Patapsco watershed to investigate the surface-subsurface flow processes in the urbanized Baltimore metropolitan region.