Baltimore Ecosystem Study Institute of Ecosystem Studies

2010 BES Annual Meeting Presentation and Poster Abstracts

A parallel integrated hydrologic model of the Chesapeake Bay Watershed : Model run times and sensitivity to grid resolution
Seck, Alimatou
Co-Authors: Alimatou Seck, Claire Welty, Reed M Maxwell

Abstract: Studies have suggested that groundwater discharge contributes significantly to the annual flows of Chesapeake Bay tributaries and is presumed to contribute to the observed lag time between the implementation of management actions and the environmental response in the Chesapeake Bay. The EPA Phase 5 Chesapeake Bay watershed model, based on the HSPF code, simulates river flow and associated transport and fate of nutrients and sediments and is used as a decision support tool. However, this model does not provide a mass-conserving representation of the groundwater fluxes in the watershed in that flow to deep groundwater is removed from model calculations. As an alternative, this study aims at the development of a fully distributed model of the Chesapeake Bay Watershed (160,000 sq km) using PARFLOW, a three-dimensional variably saturated groundwater flow model integrated with an overland flow component. The model is run on high performance computing facilities, thus allowing for applications at large scale with efficient run times. We present here parallel run times and some considerations regarding the overland flow component of the model. 4-km, 2-km and 1-km gridding resolutions were tested, with various DEMs sources and processing techniques. These tests indicated the use of a 1-km grid as the horizontal resolution for the model owing to the poor results with larger grid sizes in properly resolving river channels and drainage. Variable results were observed through the five physiographic provinces present in the model domain, with drainage being more problematic in the Blue Ridge and Valley and Ridge provinces.