 The United States Geological Survey operates fifty @-@ one stream gauges along the Missouri River . The river 's average discharge at Bismarck , 1 @,@ 314 @.@ 5 miles ( 2 @,@ 115 @.@ 5 km ) from the mouth , is 21 @,@ 920 cu ft / s ( <unk> m3 / s ) . This is from a drainage area of 186 @,@ 400 sq mi ( 483 @,@ 000 km2 ) , or 35 % of the total river basin . At Kansas City , 366 @.@ 1 miles ( <unk> @.@ 2 km ) from the mouth , the river 's average flow is 55 @,@ 400 cu ft / s ( 1 @,@ 570 m3 / s ) . The river here drains about <unk> @,@ 100 sq mi ( 1 @,@ 254 @,@ 000 km2 ) , representing about 91 % of the entire basin . 
