Nutrient Management Case Studies

Narragansett Bay Nitrogen

A case study involving an integrated and sustainable research and management approach is focusing on Narragansett Bay in Rhode Island, including its watershed and air shed. Researchers are investigating how changes in nitrogen release into water bodies and climate impact watersheds and water quality. The research will be used to help restore and protect watersheds and highly valued water resources. Researchers are:

  • Investigating how nitrogen from different sources interacts with other pollutants (such as phosphorus, sulfur, and mercury) and affects lakes and reservoirs
  • Analyzing variations in nitrogen and phosphorus fluxes through the watershed to Narragansett Bay and how nutrient management decisions have impacted ecosystem structure, function and health in the watershed and estuary
  • Developing computational tools for more informed nutrient management, and contributing to the scientific basis for comprehensive ecosystem-based management plans designed to help restore and sustain our valued water resources.

The management approaches and computational tools developed based on this research will be adaptable for use in other threatened water systems across the country.

Gulf of Mexico Hypoxia

Hypoxia is a condition of low oxygen in the water than can kill fish and other aquatic animals. The world’s second largest hypoxic zone is located in the northern Gulf of Mexico, which is referred to as the Dead Zone. The main cause of hypoxia in the Gulf is high levels of nitrogen and phosphorus that are discharged by waters from the Mississippi River Basin.

EPA researchers are developing state-of-the-art 3-D water flow and water quality models of the northern Gulf of Mexico Dead Zone as well as the Mississippi River Basin. The research is being done to understand the multiple nutrient sources, nutrient movement patterns, and impacts along the freshwater Basin and through to the Gulf’s marine environment.

The models can be used to better understand how potential nutrient management and climate change scenarios will affect the northern Gulf hypoxic area and water quality throughout the Mississippi River Basin.

Yakima River Basin

EPA and US Geological Survey researchers are working together to identify sources and impacts of nitrogen in the lower Yakima River Basin, a local source of drinking water. Using USGS and EPA data and models, researchers are working to pinpoint the major sources of nitrogen pollution and track its movement through groundwater in the Basin.

With this information, local leaders can improve groundwater quality by better understanding how nitrogen pollution affects drinking water supplies.

Guánica Bay

The multi-Agency U.S. Coral Reef Task Force initiated a program to address sediment and nutrient pollution of coral reefs in the Puerto Rico’s Guánica Bay watershed.

Municipal and agricultural growth in the Guánica Bay watershed has improved socioeconomic conditions, but also has reduced forest cover, impacted the quality and availability of drinking water and increased sediment and nutrient runoff. This runoff has adversely affected coastal sea grasses, mangroves and coral reefs. Research is providing information on the costs and benefits of using environmental resources and identifying options for supporting sustainability in the Bay.


EPA is working with the U.S. Geological Survey and the state of Iowa to develop methods for lowering sediment and nutrient pollution in surface waters draining into the Mississippi River Basin. The results of this research will help protect and restore watersheds and improve water quality throughout the entire Midwest.