HISTORY OF THE WEST FORK OF THE DES MOINES RIVER

Between 16,500 to 22,000 years ago, the entire Des Moines River watershed north of the city of Des Moines was covered by a thick sheet of ice referred to as the Des Moines Lobe of the Wisconsin Glacier. As temperatures began to warm, this sheet of ice began to slowly retreat northward. This recession was punctuated by several brief period of advancement which left behind elevated ridges referred to as moraines. Moraines are deposits of glacial debris which form when the margins of the glacier remain in place for an extended period of time.

The first of these moraines to form was the Altamont which extends south to north in the southwestern corner of Emmet County. The second moraine formed was the Algona, which lies just east of the Altamont moraine in Emmet County. Because these two moraines did not merge, a natural valley was formed between the two moraines which provided a natural waterway for melting glacial water. As a result of erosional forces, a narrow, steep sided valley formed in Emmet County which would eventually become home to the West Fork of the Des Moines River.

Over a period of hundreds of years, this valley continued to erode northward into Minnesota, eventually reaching a river system which extended from Lake Shetek south through the Iowa Great Lakes and eventually into the Missouri River. In a geological process referred to as stream piracy, this flow was captured west of Windom, Minnesota and carried south by the Upper Des Moines River. Not only did this stream piracy give rise to the current day West Fork of the Des Moines River, it also resulted in the preservation of the Iowa Great Lakes.

ECWTA wishes to thank Iowa Lakes Community College Professor Gary Phillips for assisting with this page.