Publication Date

5-2011

Abstract

This study examines the effects of various environmental conditions on the behavior of a

contaminant spill as it travels across the Wachusett Reservoir. The reservoir, located in central

Massachusetts, is a 65 billion gallon water body that supplies drinking water to the Boston

Metropolitan area and consists of numerous inflows and outflows. The Quabbin Reservoir, a

412 billion gallon system, accounts for close to half of the inflow. The Wachusett Reservoir

receives Quabbin water through the Quabbin aqueduct located on its eastern side. CEQUAL

W2, a two-dimensional, laterally averaged, hydrodynamic and water quality model was utilized

to perform numerous simulations. The current version, version 3.6, was used due to its

computational speed and ability to apply past years data without changing input files.

Four years were analyzed, 2003-2006, in order to examine similarities and differences from year

to year. Simulations for years 2005 and 2006 were calibrated to measured temperature and

conductivity profiles within the North Basin of the Wachusett Reservoir (Years 2003 and 2004

were completed prior to this research). Simulations were performed in order to better understand

the behavior of the spill under three main scenarios: 1) seasonal change, 2) variation of spill

temperature, and 3) turning the Quabbin transfer on or off. Spill characteristics and location

were kept the same for each simulation to allow for comparison. The date of the spill was

chosen based on similar wind conditions for each season of every year. The behavior of the spill

was evaluated by analyzing conductivity versus time at the withdrawal of the reservoir, the

Cosgrove intake. Profiles of conductivity versus water depth at some locations along the

reservoir were observed in order to better understand spill behavior.

Model results demonstrated that similarities between years existed. The arrival time of the spill

was affected by the seasonal change. Spring spills consistently arrived at the withdrawal within

2-3 days, fall spills within approximately 7-10 days, and summer spills took 10-15 days. The

summer spills showed more variability, having larger peaks than the other seasons. Changing

the temperature of the spill displayed minimal effect for the spring and fall seasons. The summer

of 2004 showed a faster arrival time at the intake for a warm spill whereas the summers of 2003,

2005 and 2006 displayed negligible differences in spill behavior when changing the spill

temperature. Altering the condition of the Quabbin transfer showed the most effect during the

summer months for all four years. Turning the transfer off for a period of two weeks after the

significantly. CEQUAL W2 V3.6 proved to be an effective tool in examining the behavior of a

contaminant spill within the Wachusett Reservoir under various scenarios. spill caused the variability of spill concentration measured at the withdrawal to dampen

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