The Mustinka and Bois de Sioux Rivers watershed is mantled by till deposits with scattered sand deposits.

The west-central and northwestern part of the watershed was covered by Glacial Lake Agassiz and the resulting land surface is a flat, lake-washed till plain. Patches and ridges of sand scattered throughout the lake plain were formed as beach ridges and offshore bars. Small, isolated areas of lake clay also occur within this area. The remainder of the watershed is glacial moraine characterized by rolling topography in all but the extreme eastern edge which has more local relief and more permanent lakes. Alluvial sand deposits are found in the eastern part of the morainal area.

The drainage area of the watershed in Minnesota is 1,429 square miles. The area includes mors of Traverse County and parts of Big Stone, Stevens, Grant, Ottertail, and Wilkin Counties.

Population within the watershed unit is about 20,000. The largest community, Wheaton, has a population of 2,102. The agricultural economy of the area is concentrated on grain farming, although some dairying is carried on. The principal grain crops are corn and oats. Flax, soybeans, and barley are also very commonly grown.

The natural vegetation in the area was largely prairie. A hardwood deciduous forest grew only on the extreme eastern edge. Today, the area is almost entirely farm land containing numerous local woodlots.

Outdoor recreation is concentrated on waterfowl and pheasant hunting. Fishing is done in Lake Traverse and in the larger lakes in the eastern part of the morainal area.