Date of Award

Winter 2018

Project Type

Thesis

Program or Major

Earth Sciences

Degree Name

Master of Science

First Advisor

Anne Lightbody

Second Advisor

Wilfred Wollheim

Third Advisor

Arthur Gold

Abstract

Decisions about dam management require weighing many tradeoffs. Among many other factors, dams and their reservoirs can reduce peak flows and retain nutrients that could otherwise cause downstream eutrophication. This study quantifies how dams and their management alter flows and nutrient retention within a coastal New Hampshire watershed. An annual nitrogen budget was estimated at Pawtuckaway Lake, a dammed reservoir within the Lamprey River watershed, through field work. Results showed that annual total dissolved nitrogen (TDN) and dissolved inorganic nitrogen (DIN) retention within Pawtuckaway Lake were close to estimates predicted by an empirical model developed by Seitzinger et al. 2002. A coupled hydrologic and biogeochemical model, the Framework for Aquatic Modeling of the Earth System, was used to estimate flood flows and DIN flux at the watershed outlet. Model results show that dams within the Lamprey River watershed decrease the magnitude of peak flows and reduce seasonal DIN export from the watershed to the coast. Modeling alternative conditions within the watershed shows how climate, land use, and dam management alter flood flow magnitudes as well as seasonal DIN export, suggesting the potential for dams to help mitigate projected climate and land use change within the region.

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