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Document Type

Open Access Dissertation

Degree Name

Doctor of Philosophy (PhD)

Degree Program

Civil Engineering

Year Degree Awarded

2016

Month Degree Awarded

September

First Advisor

John E. Tobiason

Second Advisor

Mi-Hyun Park

Third Advisor

David P. Ahlfeld

Fourth Advisor

Christine E. Hatch

Subject Categories

Civil Engineering | Environmental Engineering

Abstract

Managing the water quality of surface drinking water sources has become an increasingly difficult task for water suppliers due to increased watershed urbanization and climate change. Changes in source water quality may affect public perceptions, treatment effectiveness, and ultimately costs to treat water to drinking standards. Although there are increased threats to current and future drinking water quality, current approaches to managing these threats are typically reactionary. Prior detailed modeling efforts of hypothetical events that may impair raw water quality allow for an understanding of constituent fate and transport, including potential maximum concentrations and travel times to the drinking water intake for constituents which may be of concern. The primary goal of this dissertation was to present proactive frameworks that utilize a hydrodynamic and water quality model to aid in developing scientifically-based management plans prior to an accidental or natural event occurring. The Wachusett Reservoir, a major drinking water supply for metropolitan Boston, Massachusetts, was used as a case study to illustrate proactive modeling efforts to quantify water quality impacts after both short and long-term potential events. This work used a process-based modeling approach to simulate reservoir hydrodynamic and water quality responses to changes in various model inputs (streamflow, constituents, meteorology) and also evaluated current and future management decisions which may mitigate water quality impacts. The approach is demonstrated through a series of proactive modeling studies conducted to evaluate water quality at the drinking water intake in response to contaminant incidences, long-term increasing air temperatures, and extreme precipitation events. For the Wachusett Reservoir, proactive contaminant modeling highlighted the importance of a rapid response by managers to contain a contaminant spill and therefore minimizing the mass of contaminant that is able to enter the water column following an event. In scenarios that simulated long term increasing air temperature increases, model results suggested increases in epilimnion and hypolimnion water temperatures, decreased ice cover, and increased stratification duration by 2112. Extreme precipitation event simulations during the spring and summer resulted in organic matter concentrations that exceeded recorded maximums at the drinking water intake while nutrients for this particular reservoir remained low. The modeling results provide valuable insights into water quality responses to changes in water body inputs and can help inform short and long-term management strategies, prior to water quality degrading events.

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