November 11, 2016

« All News

Marissa Simpson Publishes In-Depth Analysis of Nitrogen Issues with Dam Removal

Marissa Simpson (Massachusetts) co-authored a paper entitled "Will Dam Removal Increase Nitrogen Flux to Estuaries?" which was published in the MDPI (Multidisciplinary Digital Publishing Institute) journal "Water" on November 8, 2016.

The paper concerns a study of 7,550 dams throughout New England and compares analyses of dam functions and benefits with individual dam attributes and effects on downstream receiving waters. Dam removal often generates improvements for safety or migratory fish passage but might increase nitrogen (N) flux and eutrophication in coastal watersheds. Marissa, whose role was to generate the geodatabase and conduct GIS analyses along with a partner, and her team focused on dams with reservoirs that increase retention time at specific points of river reaches, creating localized hotspots of elevated N removal.
The conclusion of the paper was that lower-order streams had the highest number of dams that create changes in the river's reach that can enhance N removal compared to an undammed state at the same location. However, fish passage and safety hazard tradeoffs must come into account when considering dams for removal.

Marissa is a GIS Specialist and the wrote the paper while a graduate student at the University of Rhode Island.

Abstract

To advance the science of dam removal, analyses of functions and benefits need to be linked to individual dam attributes and effects on downstream receiving waters. We examined 7550 dams in the New England (USA) region for possible tradeoffs associated with dam removal. Dam removal often generates improvements for safety or migratory fish passage but might increase nitrogen (N) flux and eutrophication in coastal watersheds. We estimated N loading and removal with algorithms using geospatial data on land use, stream flow and hydrography. We focused on dams with reservoirs that increase retention time at specific points of river reaches, creating localized hotspots of elevated N removal. Approximately 2200 dams with reservoirs had potential benefits for N removal based on N loading, retention time and depth. Across stream orders, safety concerns on these N removal dams ranged between 28% and 44%. First order streams constituted the majority of N removal dams (70%), but only 3% of those were classified as high value for fish passage. In cases where dam removal might eliminate N removal function from a particular reservoir, site-specific analyses are warranted to improve N delivery estimates and examine alternatives that retain the reservoir while enhancing fish passage and safety.

More Information

For more information regarding the article, visit: Water
For more information on nitrogen flux to estuaries, contact Marissa Simpson at This email address is being protected from spambots. You need JavaScript enabled to view it..
To connect with Marissa Simpson see her profile at: https://www.linkedin.com/in/marissa-simpson-a0603ba4