The Cumulative Impacts of Climate Change and Land Use Change on Water Quantity and Quality in the Narragansett Bay Watershed

Elisabeth Hamin, for their guidance in constructing the project and for posing important questions that helped drive the design of the project. I would especially like to thank Tim Randhir for working with me to build the model. I would also like to thank Nancy Sammons and Raghavan Srinivasan for their extensive support in troubleshooting problems with the model. Their willingness to take time to field questions and examine my model inputs for errors was pivotal to the success of the project. I also thank the contributors to the ArcSWAT Google Group who shared their expertise on SWAT, ArcSWAT and SWAT-CUP. Thank you to the College of Natural Sciences, Dean Martha Baker and Deborah McCutchen for proving me a means to fund my graduate studies. Finally, I would like to thank all my peers in my graduate cohort for their support, encouragement and occasional commiseration. Narragansett Bay, Rhode Island, is a valuable natural resource that suffers summer hypoxic events resulting from over a century of cultural eutrophication. Current efforts to reduce nitrogen loading from wastewater treatment facilities discharging into the Bay and its tributaries hold the promise of working towards ecological restoration. But, the efficacy of these efforts may be limited, or undone, if future changes in climate or land use increase nutrient and sediment loads to the Bay. This study developed a SWAT model of the upper Narragansett Bay watershed to simulate water quantity and quality. The baseline model was calibrated and validated to accurately reflect watershed behavior. I then used the model to simulate water quantity and quality under an altered climate, with an IPCC projected increase in temperature of 3°C and a 10% increase in precipitation by 2080. A second scenario incorporated projected 2080 land use in the absence of climate change. The third scenario combined the climate change and land use change alterations to examine cumulative impacts. A comparison of scenario outputs against the baseline simulation highlighted the expected impacts climate change and land use change will have on the watershed. Both climate v change and land use change demonstrated impacts on surface runoff, water yield, PET and ET, streamflow, and loading of sediment, organic N, organic P and nitrate. Climate impacts were much greater than land use impacts, but land use impacts displayed greater regional variation. The results of the combined simulation indicate that future climate and land use change will likely negatively impact the …