New USGS NAWQA Maps and Tables Describe Nutrient Loading to Gulf of Mexico from Mississippi and Other River Basins

Map of River Basins Feeding Northern Gulf of Mexico

The USGS National Water-Quality Assessment (NAWQA) Program has made new maps and data tables available on line that describe nutrient loading to major estuaries throughout the U.S. (available on the NAWQA "Tracking the Source and Quantity of Nutrients to the Nation's Estuaries" web site). These new data presentations describe the major sources and contributing areas of nutrients to 115 estuaries along the coastal U.S., including nutrient loading from the Mississippi River Basin, and other watersheds into the Gulf of Mexico.

The maps and tables were produced using the USGS SPARROW (SPAtially Referenced Regressions on Watershed attributes) nutrient models. The SPARROW models incorporate geospatial data on geology, soils, land use, fertilizer, manure, wastewater treatment facilities, temperature, precipitation and other watershed characteristics.  The data are provided from USGS, NOAA, USDA, and USEPA, and are linked to stream flow measurements  from USGS streamgages, as well as water quality data from over 2,700 sampling locations operated by 73 monitoring agencies. 

In addition to the new web pages, persons interested in a particular stream can now utilize an online, interactive SPARROW model Decision-Support System (DSS) to estimate how reductions in upstream nutrient sources affect downstream nutrient loads at a stream outlet. A new reporting feature within the DSS provides summary information on the amounts and sources of nutrients from upstream states and major hydrologic regions (for example, the amount of nitrogen contributed from each of the 31 states that drain into the Gulf of Mexico from the Mississippi River Basin).

This combination of national maps and an online decision support system is designed to improve access to water quality modeling information that can then further of nutrient reduction strategies and inform nutrient management policies.

Additional information on USGS nutrient monitoring and modeling activities by the NAWQA program are available online.

[The above is modified from a February 25 USGS NAWQA release regarding the new maps and tables]