Prairie Potholes

What is a Prairie Pothole?
Prairie Potholes are depressional wetlands that were formed by glacial activity. As glaciers retreated, they left behind “potholes” throughout the landscape. These depressions, caused by the uneven deposition of glacial till (soil, rocks, and other debris picked up by the glacier), the scouring action of glaciers, and the melting of large, buried ice blocks, are known as prairie potholes.
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Prairie Pothole Region
The prairie pothole region (PPR) of North America covers approximately 276,063 square miles. This region covers north-central Iowa and extends up northwest to central Alberta. This region was formed primarily by glacial events that happened during the Pleistocene Epoch, which lasted from about 2.6 million to 11,700 years ago. The last glaciers retreated from the PPR about 12,000 years ago, leaving the region dotted with prairie potholes.

The PPR is one of the most important wetland regions in the world. The many shallow lakes and marshes, rich soils, and diverse flora and fauna allow more than 50% of North American migratory waterfowl, such as pintail, gadwall, and shoveler, to make their home in the PPR. Many species depend on the potholes for breeding and feeding. Prairie potholes provide habitat for many other species of animals, such as grassland birds, waterbirds, and shorebirds.
Prairie potholes absorb surges of rain, snow melt, and floodwaters thus reducing the risk and severity of downstream flooding.
The PPR has been altered greatly by agricultural and commercial development. Many pothole areas have been drained with field tile and drainage ditches to allow the areas to be farmed or for commercial development. But this has led to increased runoff and more severe flooding during large rain events because the natural function of the potholes to hold and slowly release water has been altered. The loss of habitat and breeding and feeding grounds has also been detrimental to the species that depend on these potholes for survival.

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