The Big Blue River is the largest tributary of the Kansas River. The river flows for approximately 250 miles (402 km) from central Nebraska into Kansas, where it intersects with the Kansas River east of Manhattan, Kansas. It was given its name by the Kansa tribe of Native Americans, who camped at its mouth from 1780 to 1830.
Shortly before intersecting with the Kansas River, the Big Blue discharges its waters into a reservoir called Tuttle Creek Lake, which lies slightly northeast of Manhattan. The reservoir is a man-made flood-control measure, held back by a dam composed of the limestone, silt, and gypsum dredged out of the floodplain by bulldozers left to rust underneath the flooded area. The land surrounding the reservoir is a state park area, although the Great Flood of 1993 decimated much of the northern area.
The river continues as the outflow from Tuttle Creek Lake for approximately five miles before intersecting with the Kansas River east of Manhattan.