Subject: New USGS Water Quality Findings: No Consistent Declines in Nitrate Levels in Large Rivers in the Mississippi River Basin


           ******Please distribute to your staff and other colleagues******

New USGS findings released in the journal of Environmental Science & Technology,accessible at: http://water.usgs.gov/nawqa/pubs/nitrate_trends/.

No Consistent Declines in Nitrate Levels in Large Rivers in the Mississippi River Basin--
Despite efforts to reduce nitrate in the Mississippi River basin, nitrate concentrations and transport at eight mainstem or large tributary sites have not declined from 1980-2008. The results are based on a new statistical method developed by the USGS that takes into account variation in river flows, in order to paint an accurate picture of long term trends. These results reflect the cumulative changes over time in nitrate sources and conservation practices throughout the Mississippi River basin, and highlight the need for comprehensive nutrient management strategies that will reduce nutrients in both streams and groundwater.

Key findings:
·        Nitrate concentrations increased considerably at two sites  (Mississippi River at Clinton, IA and at Missouri River at Hermann, MO)
·        Nitrate concentrations remained very nearly the same or increased at the other six sites
        (Iowa River at Wapello, IA; Illinois River at Valley City, IL; Ohio River near Grand Chain, IL; and along the Mississippi River at Grafton, IL; at Thebes, IL; and near the Old River Outflow Channel)
·        Nitrate transport to the Gulf of Mexico increased from 1980 to 2008
·        Increases in nitrate concentrations in groundwater are having a substantial effect on nitrate concentrations in rivers and transport to the Gulf of Mexico. The evidence for this comes from the fact that increases in nitrate concentrations are particularly large during low flow conditions.

Contacts:
Lori Sprague, [log in to unmask], 303-236-6921
Robert Hirsch, [log in to unmask], 703-648-5888


_____________________________________________
Mike Woodside
USGS -- National Water-Quality Assessment Program
640 Grassmere Park, Suite 100
Nashville, TN 37211
615-837-4706
http://water.usgs.gov/nawqa/
_____________________________________________

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