IMPACT OF NEW ENGLAND DAMS ON FLOOD FREQUENCIES AND NITROGEN FLUX

Decisions about dam management require weighing many tradeoffs and considering many ecosystem services. Among many other factors, dams and their reservoirs alter the timing, magnitude, and frequency of low and high flow events. In some cases, these modifications negatively impact aquatic ecosystems, but dams can also be managed to attenuate peak flows, reduce potentially catastrophic low flows, increase lentic habitats in impoundments, and retain nutrients that otherwise would be exported to sensitive coastal waterbodies. A combination of historical gauge data and field observations were used to explore how dams and their management alter flows and nutrient retention within watersheds across New England. In addition, a numerical watershed model was used to explore how climate, land use, and dam management alter flood flow magnitudes and seasonal DIN export within a coastal watershed. Dams located closer to the headwaters have a greater potential to mitigate downstream flooding while dams on the main stem play a larger role in nutrient attenuation. Thus, the spatial location of dams as well as anticipated future land use and climate changes should be considered when making dam management decisions.