Nearly 50% of Minnesota’s stream miles have been physically altered by humans, according to a first-of-its-kind research project. Alterations like channelizing, ditching, or impounding change the natural hydrology of streams and their drainage areas. These changes can result in higher flows, loss and disturbance of habitat, and higher levels of pollutants entering streams and lakes.
People in Minnesota have modified and rerouted rivers and streams to accommodate various aspects of human development and entrepreneurship for more than 100 years. However, the extent of altered stream miles within Minnesota has not been well documented until now.
Over the past two years, the MPCA and MNGeo have been visually reviewing stream channels using a combination of available sources including:
- Aerial imagery from the previous 30 years
- Historical aerial imagery dating back to the 1930s
- Very recent LiDAR imagery (high resolution elevation data)
- MPCA biological monitoring photographs
The results indicate that 49.6% of stream miles in Minnesota have been altered by humans, a higher percentage than previously thought by watershed professionals. The results also represent the first comprehensive baseline of stream channel conditions in the state of Minnesota.
Having comprehensive data on the extent of watercourse alterations will help ongoing monitoring efforts. Altered stream channels can result in higher flows, higher levels of pollutants entering waterways, and decreased habitat. Water quality monitoring results can now be compared with the altered watercourse data to help the MPCA determine potential causes of pollution problems within a given watershed.
This combination of information will also assist the MPCA in working with local partners to develop watershed restoration and protection plans throughout the state’s major watersheds. Restoring an altered stream to its natural condition, or maintaining a stream that has not been altered, can aid in protecting or improving water quality.
“This information will be very helpful as we continue to monitor and assess the condition of Minnesota’s rivers, streams, and lakes,” said MPCA stream biologist Ben Lundeen. “It will help our watershed staff as they continue to work with local partners to develop watershed restoration and protection projects throughout the state.”
With funding made available through the Clean Water, Land and Legacy Amendment, the Altered Watercourse Project was a collaborative effort between the Minnesota Pollution Control Agency, the Minnesota Geospatial Information Office (a program of MN.IT Services), and the Minnesota Department of Natural Resources.
For more information
- MPCA's Minnesota Statewide Altered Watercourse Project webpage.
- MNGeo Altered Watercourse Project webpage.