The West Osage River Basin lies in the west-central Missouri counties of Bates, Vernon, St. Clair, Barton, Henry, Cedar, Benton, Hickory and Polk (Figure Lo01). It starts at Harry S. Truman Dam near Warsaw, Missouri, and contains the Osage River and all tributaries except the South Grand, Pomme de Terre and Sac rivers. The watershed encompasses 2,795 mi2 in Missouri and 4,046 mi2 in Kansas (Missouri Department of Natural Resources [MDNR] 1984, U.S. Army Corps of Engineers [COE] 1985). Hereafter, the term "basin" will refer to the entire West Osage River Basin, unless otherwise specified.
The Osage River originates at the confluence of the Bates County Drainage Ditch and Marmaton River northwest of Schell City, Missouri, in northeast Vernon County. It ends at its junction with the Missouri River (RM 130.2) east of Jefferson City, Missouri, in Osage County. The original length of the river was 310 miles; 193 miles have been impounded by Bagnell and Truman dams, 22 miles have been channelized and 95 miles lie below Bagnell Dam (MDNR 1986a). Truman Dam impounded 98.5 miles of the Osage River in November 1979.
The basin is divided into six subbasins to facilitate discussion of the large, diverse area (Figure Lo02). Hereinafter, the subbasin will be referred to by the first stream listed below:
- Weaubleau Creek, Hogles Creek and Bear Creek
- Monegaw Creek and Gallinipper Creek
- Clear Creek
- Marais des Cygnes River
- Marmaton River and Little Osage River
- Dry Wood Creek and Little Dry Wood Creek
Several smaller tributaries within the basin also are included, however, most of these streams are impacted by Truman Lake.