Date of Award
Campus Access Thesis
Master of Science (MS)
Global change drivers, such as land use land cover (LULC), affect a watershed’s hydrologic regime and stream biotic life. As the amount of impervious surface increases in a watershed, the amount of stormwater and nutrient flux also increases, reducing stream water quality. In 2012 and 2013, physical and chemical data were collected in conjunction with the United States Environmental Protection Agency (US-EPA) Streamside Biosurvey for Macroinvertebrates (SBM) for ten sites throughout the Charles River Watershed (CRW). Afterward, Geographic Information Systems (GIS) was used to gather LULC and impervious cover data at the regional sub-watershed and local buffer scale. In order to determine the influence of development on stream biotic life, and ultimately water quality, a path analysis model was developed exhibiting different direct and indirect effects amongst hierarchical scale variables. Hierarchical differences in effects of development existed when compared between the buffer and sub-watershed scale. At the buffer scale, water quality was influenced more negatively by the percentage of developed land area versus the percentage of impervious cover. While both buffer development and habitat quality had a direct effect on SBM, buffer development also directly hindered habitat quality, therefore having an indirect effect on SBM through habitat. SBM scores were shown to be more sensitive to development within the buffer versus at the sub-watershed scale where impervious cover was a more important indicator of stream water quality. While the path analysis showed the importance of impervious cover at the sub-watershed scale and the importance of percent development and habitat quality at the buffer scale, MapShed complemented the path analysis by providing sediment, nitrogen, and phosphorus loads and their sources for the CRW. The MapShed model assisted in developing management strategy recommendations for the Charles River Watershed Association (CRWA) including reducing impervious cover, stabilizing stream banks, and constructing vegetative buffers and bioretention areas. Over the long term, the key to improving water quality in the CRW stems from making watershed-scale management changes in an effort to reduce nutrient loads, improve the quality of habitat, and minimize our alteration of the natural flow regime, potentially leading to improved water quality.
Gulich, Laurissa C., "Path Analysis of Hierarchical Drivers On Water Quality in the Charles River Watershed Tributaries, Massachusetts" (2016). Graduate Masters Theses. 376.