Water Quality Modeling and Assessment of the Wachusett Reservoir & Watershed

Intro

The 4,135-acre Wachusett Reservoir was built between 1897-1908 by damming the South Branch of the Nashua river. Wachusett Reservoir is the terminal supply reservoir of the of the MWRA system, feeding the new J.J. Carroll Water Treatment Plant. Together with the Quabbin reservoir, they provide an clean source water to 47 communities, 2.2 million people and 5,500 industrial users in the metropolitan Boston area. The UMass project is aimed at providing assistance in several key areas to the Department of Conservation and Recreation (DCR), the body responsible for collection and safe storage of the source water, protection of reservoir water quality, and management of the watersheds. In particular they are helping to improve DCR's understanding of the fate and tranport of contaminant in the researvoir (Project 1), to design better monitoring programs and predictive models for nutrients in the watershed (Project 2), and to develop pathogen source tracking tools (Project 3).

Project 1 : Reservoir Modeling

Mathematical models can provide the ability to predict the response of DCR reservoirs to a variety of influences, allowing the models to be used as aids for operational decision making or for making long-term policy decisions. Factors that influence reservoirs include those, which may be outside of DCR control, such as loadings of water quality constituents, hazardous waste spills, and extreme weather events. Other factors such as water release and transfer policies, water quality control procedures, and watershed protection practices may be controllable by DCR or MWRA. Both reservoir water quantity and quality respond to these various influences. For models to be effective tools they must be proven to be reliable predictors of reservoir behavior when tested against a substantial body of data.

In this research , UMass will model processes at the Wachusett Reservoir using the two-dimensional CE-QUAL W2 model and the three-dimensional FLUENT model has been applied to the Thomas Basin portion of Wachusett Reservoir. This work will include developing and maintaining model-ready databases and calibrated models for Wachusett Reservoir. The current project has three specific objectives: continued improvement of hydrodynamic models and evaluation of alternative 3-dimensional modeling options, support of the MWRA financed bathymetry and hydrodynamic data gathering effort, and continued water quality modeling via CE-QUAL W2 with a focus on microorganism transport.

Project 2: Watershed Dynamics and Management

Constituent inputs to drinking water reservoirs from nonpoint sources are a major concern for public drinking water providers such as the DCR. Knowledge of the input loads and transport pathways of constituents such as pathogens, nitrogen, phosphorus, and sediment can lead to better reservoir operation; and control at their source can be a cost-effective solution for drinking water concerns. Watershed modeling, in combination with focused data collection efforts, has the potential to extend our understanding of contaminant sources, fate and transport. Of particular interest is determination of the relative contributions of point and non-point sources to annual load. Of equal interest is demonstration of the success or failure of ongoing efforts for protection of water quality, including storm sewer hookups, site specific best management practices, and land acquisition. Accurate quantification of hydrologic variability is critical for understanding the associated long-term watershed and reservoir water quantity and quality affects, particularly under future climate change scenarios. These topics are the focus of Project 2: Watershed Dynamics and Management.

The Watershed Dynamics and Management project is divided into three interrelated components: 1) development and evaluation of effective monitoring strategies, 2) models for quantifying load and discharge, and 3) methods for evaluating and quantifying the impact of watershed management practices. Each component is described below. The third component will be completed in cooperation with Project #3,. Through this work UMass will more closely link land use information and water quality data in order to develop more useful and robust watershed management strategies.

Project 3: Source Water Protection Activities - Indicator and Pathogen Source Tracking and Assessment

The need for water utilities, especially those using unfiltered surface water sources, to remain proactive regarding source water protection and watershed management activities has been re-emphasized under recent provisions of the Clean Water Act and the Long Term 2 Enhanced Surface Water Treatment Rule. Nationwide, utilities are concerned with balancing pressures from growing populations for developable land and land protection/conservation in drinking water watersheds. In this context, the DCR is no different. In this current economic and political climate, acquisition of lands by DCR to ensure maintenance of land in its natural state is becoming more and more challenging. Therefore, increased vigilance in monitoring can identify potential problems before they actually become problematic. Thus, this project proposes to continue the collaborative research program focusing on questions of microbial source tracking methods applicable for DCR use, and impacts on water quality from changes in land use ( i.e. sewering and application of BMPs).

Completed DCR funded projects, in conjunction with American Water Works Association Research Foundation projects, have established the efficacy of three source tracking indicators (sorbitol-fermenting Bifidobacteria indicating human wastewater, Rhodococcus coprophilus indicating grazing animal wastes, and F+RNA coliphage serotyping distinguishing between human and non-human wastes) for use as part of DCR watershed management activities. As a result of the DCR funded research, these indicators are also starting to be tested by other water utilities. This project is focusing on developing molecular-based methods for R. coprophilus , so as to shorten analysis time. In addition, more rapid test protocols will allow for more rapid mobilization for forensic studies of coliform excursions.

 

Principal Investigators

Research Assistants

  • Erich Fiedler, Cynthia Castellon, Mary Serdakowski, Christina Stauber

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