Dams, nutrients, and water quality: A study of time-explicit reservoir ecological functions in the Chesapeake Bay Watershed

Keywords: River damming, Water quality, Chesapeake Bay, Process-based model
Abstract Type: Paper Abstract

Abstract

River damming has been practiced to provide irrigation and power, and to prevent downstream flooding. The reservoirs behind these dams impede water and increase residence times along the land-ocean aquatic continuum, leading them to act as sediment traps and in-stream reactors for nutrients. The Chesapeake Bay Watershed is home to more than 1400 reservoirs, from small mill dams to the large Conowingo Dam on the lower Susquehanna River. But despite both the regional and global importance of reservoirs to water quality and aquatic ecosystems, we continue to have a limited understanding of how these hydrologic structures impact the sink and flow of legacy contaminants, and of how these effects may change under future scenarios, including a warming climate, aging infrastructure, and dam removal. In this work, (1) we address the need for more comprehensive reservoir dataset by presenting open-source geo-referenced database of dams to date in the Chesapeake Bay region, containing their location and other associated information (2) We use both data synthesis and 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 on the achievement of the Chesapeake Bay total maximum daily load (TMDL). Our preliminary work suggests that water residence times vary considerably for these reservoirs, from days to a year, as a function of both reservoir size and river discharge magnitudes to the individual water bodies, and their corresponding nutrient retention functions continue to change under different future scenarios.