Feb. 24, 2014 -- As a means to highlight the major sources and watershed inputs of nutrients to the Great Lakes and estuaries along the Atlantic coast, Gulf of Mexico and Pacific Northwest, the U.S. Geological Survey (USGS) has provided new interactive maps and tables on their website (available here).
Nutrient enrichment of U.S. streams, lakes and estuaries is widespread and can contribute to harmful algal blooms, ultimately increasing costs for drinking water and causing declines in ecosystem health. As such, these new resources illustrate major sources of nutrients and areas within a watershed that contribute the largest amounts of nutrients to 115 estuaries along the coastal areas and from 160 watersheds draining into the Great Lakes.
Accordingly, the data can also serve further uses. For instance, water resource managers interested in a particular stream or estuary can use the online, interactive decision support tool to estimate how changes in nutrient inputs (source, type and amount) affect nutrient loads at a downstream location. A new reporting feature within the tool also provides summary information on the amount and source of nutrients from upstream states or major hydrologic regions. For instance, output from the new tool shows the amount of nitrogen contributed from each of the 31 states that drain from the Mississippi River Basin into the Gulf of Mexico.
"This innovative combination of national maps and an online decision support tool provides unparalleled access to water-quality modeling information," said Jerad Bales, USGS acting associate director for Water. "It can be used to improve nutrient reduction strategies and inform nutrient policies across the nation."
These maps and data tables were produced using the USGS Spatially Referenced Regressions On Watershed attributes (SPARROW) nutrient models to explain spatial patterns in stream nutrient loads in relation to human nutrient inputs and natural processes and sources. Successful management of U.S. waters requires an integrated approach that includes both monitoring and modeling to understand the affect, source type, input amounts, and performance of management activities on nutrients in local streams and ultimately in the nation's estuaries.