Solving the Sediment Mystery

On October 16, the Brown-Nicollet-Cottonwood Water Quality Board accepted a 319 grant (federal dollars funneled through the Minnesota Pollution Control Agency) for a Sediment Finger Printing project in the 7 Mile Creek Watershed in Nicollet County. The grant, amounting to $84,900, will be used to do water tests to determine where the sediment in the water originates. Approximately 5,000 tons of sediment per year is coming from the watershed and being deposited into the Minnesota River."Now that we know how much, the next question we need to answer is where is it coming from", says Kevin Kuehner, Water Quality Specialist/Coordinator with the agency. It is the goal to take 20 to 30 samples each year from four different sites in the watershed.
The testing of the water is very specialized and expensive. It involves using a proton excellerator and only a few places in the United States do these kinds of tests. Sediment fingerprinting uses specialized tests to identify natural and man-made tracers found in the soil that are unique to certain sediment sources within a watershed. For instance, one tracer that will be used is Lead 210, a natural isotope that is the result ofthe decay of uranium and radon gas. This particular isotope can be used to help distinguish sediment derived from upland cultivated land versus sediment derived from stream banks, bluffs, gullies or ravines."Ultimately, with this information we can do a better job managing our watersheds and targeting conservation practices in the Minnesota RiverBasin", states Kuehner.
The demonstration project will be funded from 2007-2009 and is a collaborative effort between many agencies including the St. CroixWatershed Research Station, Pollution Control Agency, University ofMinnesota, Minnesota Science Museum and the National Center for EarthSurface Dynamics. end