Point source controls have been the primary methodology utilized to reduce pollutant loads into the waterways of the United States for the last 30 years. However, the complex dynamics that occur in the water column, in conjunction with increased amounts of urbanization in our watersheds, have made point source controls alone inadequate for solving our nation’s water quality problems. In order to determine the impacts that various water quality management strategies will have on water quality, dynamic models capable of simulating the complex interactions in both the water column and the watershed are necessary.

The Blackstone River Water Quality Study was implemented to determine the impact of ongoing and proposed upgrades at wastewater treatment plants on water quality along the Blackstone River and the magnitude of corresponding reductions in pollutant loads into Narragansett Bay. The impacts of changes in land use in the surrounding watershed on water quality in the Blackstone were also analyzed as part of the study.

The study utilizes an HSPF hydrologic model developed for the Blackstone River by the USGS. UMass and CDM then added water quality simulation capabilities to the model as well as discretizing the mainstem and extending its simulation period. The model continuously simulates water quantity and quality across 100+ reaches used to model the Blackstone River watershed for the period from 1996-2007. As part of the study, the construction, calibration and error bound of the model are detailed as well.

Based on the results of model simulations, it is shown that improvements in instream water quality as well as decreases in the downstream pollutant transport are achieved through ongoing and proposed point source control strategies. However, it has also been shown that non-point source controls can also achieve the same instream improvement and pollutant reduction as the proposed point source controls in the watershed. Despite the significant improvements in water quality observed during the model simulations, none of the pollution reduction strategies, including the removal of all point source loads from the system allow the Blackstone River to achieve ambient water quality standards as recommended by the U.S. Environmental Protection Agency.