Large open lead at Cosna Bluff No flash player has been set up. Please select a player to play Flash videos. Video not playing? Update your browser or download the video clip Espen Jervsjo explains how fast moving water through here freezes up later than other parts of the river, leaving a large open lead that often is present as late as January. Process Observed: Open Water (Lead)Late FreezeupTurbulent Water Date Process Observed: Wednesday, March 2, 2011 Galleries: Cosna Bluff Gallery