The U.S. Geological Survey (USGS), in cooperation with numerous local, state and other federal agencies currently operates more than 52 real-time nitrate sensors across the nation to monitor nitrate runoff. This cutting-edge optical sensor technology is being used in the Mississippi River basin to more accurately track the nitrate pulse from small streams, large tributaries and ultimately track nitrate runoff all the way to the Gulf of Mexico.

Excessive springtime nitrate runoff from a variety of sources, including agricultural land, in the Mississippi drainage zone eventually flows into the Mississippi River. When it arrives downstream, excess nitrate contributes to the Gulf of Mexico hypoxic zone, an area with low oxygen known commonly as the "dead zone."

These optical sensors measure and transmit nitrate data every 15 minutes to three hours and are located at the mouth of the Mississippi River near Baton Rouge, LA, and at several large tributaries to the Mississippi River—including the Missouri River at Hermann, MO; Ohio River at Olmsted, IL; Ohio, Illinois River at Florence, IL; and Iowa River at Wapello, IA – to track how nitrate concentrations from different areas of the watershed pulse in response to rainfall and seasons.

"Real-time information will improve our ability to measure the effectiveness of management actions by allowing us to track the movement and quantity of nitrate delivered from small streams all the way to the Gulf Coast," said Lori Caramanian, the Department of the Interior’s deputy assistant secretary for Water and Science. "These sensors will give us an unprecedented level of precision in tracing the origins of excessive nitrate, and will be a valuable tool in tracking progress toward the goal of reducing the size of the dead zone."

Read more about the optical sensor monitoring project at http://www.usgs.gov/newsroom/article.asp?ID=3668.