How the upper Mississippi goes from pristine to polluted
The Mississippi near Bemidji is the untainted river of our imagination.
As it travels south of St. Cloud, however, the pollutants start pouring in, and by the time the historic waterway hits Minneapolis, the fish are often under consumption advisories and the water is sometimes unsafe for swimming.
A comprehensive new study finds the majestic river under growing threats from changes in the landscape of central Minnesota and warns that growing levels of nitrates, primarily from fertilizer, threaten its safety for drinking.
The two-year study, released Wednesday by the Minnesota Pollution Control Agency (MPCA), is the first comprehensive look at the health of the upper Mississippi, the entire 510-mile stretch from Lake Itasca to the Twin Cities and its surrounding landscape. As a result of new measurements, 274 more miles of the river will be added the state’s “impaired waters” list, bodies of water that fail to meet at least one water quality standard.
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The agency did not release the 186 pages of water quality data it compiled, but posted a six page summary on its website.
Key findings:
• Water quality is “almost pristine near the headwaters” because less of the land has been altered, and many forests and wetlands have survived.
• Streams and rivers joining the Mississippi are the major sources of degradation.
• Where the Crow River joins the Mississippi, south of St. Cloud, nutrient pollution doubles.
• Nitrate levels still meet safe drinking standards, but are rising.
More..
http://www.startribune.com/how-the-upper-mississippi-goes-from-pristine-to-polluted/411707016/
