Control lock
A control lock, guard lock or canal lock in that its primary purpose is controlling variances in water level rather than raising or lowering vessels. A control lock may also be known as a tide lock where it is used to control seawater entering into a body of fresh water.
Examples
The T. J. O’Brien Lock and Dam at
Chicago, Illinois is a guard lock that controls the outflow of water from Lake Michigan into the Illinois Waterway while locking vessels through between the waterway and Lake Michigan.[1]
Lock 8 near the south end of the
Port Colborne, Ontario, Canada is a guard lock. Due to the large expanse of shallow water in Lake Erie
, changes in wind direction and force create water level changes as great as 11 feet (3.4 m) at Port Colborne. Lock 8 controls the water level in the canal, keeping it independent of the fluctuations of Lake Erie, but allows ships to enter Lake Erie regardless of its level.