During low-flow periods, salty water from the tidal part of the Caloosahatchee River moves upstream during boat lockages at the W. P. Franklin Darn near Ft. Myers, Florida, as shown on figure L Salty water enters the lock chamber through openings of the downstream sector gates which separate tidal and fresh water; when the upstream gates open, some of the salty water moves into the upper pool, probably as a density current. Repeated injections of salty water cause a progressive increase in the salinity of the upstream water. The salty water moves upstream within the deeper parts of the river channel as far as 5 or more miles above the lock. Some mixing of the high-chloride deeper water and the fresher shallow water occurs in the affected reach above the lock, probably as a result of wind and waves, and turbulence created by boat traffic.
