The clear waters of the Missouri River meet the muddy waters of the Dearborn River. During high water on the Dearborn River the water runs muddy. As such, when the Dearborn flows into the Missouri it makes the waters of the Missouri muddy, too. Thus, anglers fishing the Missouri will want to stay upstream of the Dearborn River confluence when the Dearborn River is running high and muddy. Happily, the "muddy waters" of the Dearborn only really occur during spring run-off - which only lasts a few weeks.