Publication Date
4-8-2008
Abstract
The purpose of this paper is to present applications of long-term and multi-faceted approaches undertaken for the Division of Water Supply Protection of the Massachusetts Department of Conservation and Recreation (DCR) in modeling hydrodynamics and water quality in Wachusett Reservoir. The modeling work is part of a larger effort focused on the two reservoir (Quabbin and Wachusett) source of currently unfiltered drinking water for the Boston metropolitan area, with the long term research goal of providing a rational basis for watershed and reservoir management decisions through measurements of water quality and modeling of significant transport and transformation processes. Modeling of reservoir hydrodynamics and water quality has included extensive use of CEQUAL W2, a two dimensional (longitudinal segments, depth layers, lateral homogeneity) finite difference model available in the public domain. Assessment and calibration of annual water budgets have highlighted strengths and weaknesses of available data in properly characterizing water quantity. Wachusett, the terminal supply reservoir, can be significantly affected by transfers from the larger, more pristine, Quabbin reservoir; modeling has illuminated key impacts of this transfer. Another aspect of the project has been to assess inputs and transformations of natural organic matter (NOM) due to its influence on subsequent oxidant/disinfectant demands and by-product formation. The current modeling work is directed as assessing potential impacts of contaminant spills (sewage, hydrocarbons) into the reservoir on water quality in the overall reservoir and at the Cosgrove water supply intake. Impacts of spill date (season) and location as well as contaminant type are being investigated through use of both the two dimensional CE QUAL W2 model and a three dimensional computational fluid dynamics (CFD) model developed for the Thomas Basin. This paper will summarize and highlight key findings from the recent contaminant spill modeling work.