Dams, Reservoirs, and Nutrients in the Chesapeake Bay Watershed: Past trajectories and Future Horizons
Abstract
River damming has been practiced for millenia to provide irrigation for agriculture, to prevent downstream flooding, and to generate both mechanical and electrical power. The reservoirs behind these dams impede water flow and increase residence times along the land-ocean aquatic continuum, leading them to act as sediment traps and in-stream reactors for nutrients. Global-scale work suggests that reservoirs in major river systems may lead to the denitrification of up to 50% of total riverine N inputs. The Chesapeake Bay Watershed is home to thousands of dams, from small mill dams to the large Conowingo Dam on the lower Susquehanna River. Recent work has shown that the biogeochemical functionality of the Conowingo Reservoir has changed over time, and that the reservoir system has become less efficient at retaining both sediments and nutrients. Other work has shown that mill dams, which have led to significant accumulation of legacy sediments and nutrients, are now contributing to increased suspended sediment loads to the Chesapeake Bay due to channel incision and widening. Across the Chesapeake Bay Watershed, however, there is little understanding of the cumulative effects of the many dams and reservoirs on nutrient loading to the Bay, and of how these effects may change under future scenarios, including a changing climate, aging infrastructure, and increased removal of small dams. Here, I will discuss the current state of knowledge regarding the changing effects of dams and reservoirs on Chesapeake Bay Watershed nutrient loads. I will then present the results of our new work, in which we use both data synthesis and a process-based modeling approach to quantify the time-varying effects of reservoirs on riverine N loading across the Chesapeake Bay Watershed, and to explore the long-term implications of these effects for Chesapeake Bay water quality.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2021
- Bibcode:
- 2021AGUFM.B44A..02V