Nearly half of Minnesota's miles of streams have been changed by human activity, according to the results of a two-year study released today.
The Minnesota Pollution Control Agency and Minnesota Geospatial Information Office looked at aerial photos dating back to the 1930s, among other data, and found 49.6 percent of stream miles in the state have been altered.
While it has been known for decades that many miles of river in the state had been altered for agriculture, logging, damming, development and other human actions, this was the first study to actually quantify how many miles no longer are running their natural course.
PCA officials said having comprehensive data on the extent of stream alterations "adds a new layer of context and perspective to ongoing monitoring efforts." It's known, for example, that altered stream channels can result in higher flows, higher levels of pollutants entering waterways and decreased habitat for fish and wildlife.
The PCA said the results will help determine potential causes of pollution problems within a given watershed. And the information will help the agency and local groups as they develop watershed restoration plans. The state has 81 major waterways.
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The project was funded by the Clean Water, Land and Legacy Amendment with a portion of the state's sales tax.
