10.1.1.2.7 Black River - RM 708.7 . The Black River is one of five principal tributaries to the Mississippi River above La Crosse whose course and drainage basins are entirely within the state of Wisconsin. It drains an area of 2,080 square miles above Galesville, Wisconsin, near its confluence with the Mississippi River, and 1,290 square miles above the Hatfield Dam near Black River Falls, Wisconsin. The river drains at least part of seven Wisconsin counties: Taylor, Clark, Jackson, Monroe, Trempealeau and La Crosse. Upstream of Black River Falls, the river flows through a region of flat to gently rolling terrain in a previously glaciated area. The drainage network is young and mainly postglacial, and valleys are shallow. There are widespread swampy areas east of Black River Falls. Compared to the upper reaches of
other river systems in the region, the slope of the Black River is relatively mild and uniform, at about 6 feet per mile, in this area. This is due to the presence of a crystalline bedrock substrate which has limited downcutting. After passing Black River Falls, the river enters the unglaciated "driftless area," an area characterized by deeply cut valleys, or coulees, above which are areas of relatively uniform tableland. Here the river flows in a meandering manner through a thick alluvial fill at a slope of about 2 feet per mile to its confluence with the Mississippi River at La Crosse, Wisconsin near Mississippi River mile 699. There are two impoundments on the Black River: Lake Arbutus, formed by the Hatfield Dam; and an unnamed impoundment formed by the Black River Dam in Black River Falls. Land use in the basin is predominately agricultural, with some recreational use around Lake Arbutus and along parts of the main Black River channel.