By "drawing-down" the water in lakes in the fall, a capacity for storage of the "spring-run-off" is created. This reduces the potential for downstream flooding in the spring.

Historically most of the dams in the park were built to support logging. Several of these dams have been allowed to deteriorate naturally. One example would be the dam that used to exist at the end of Lake Travers. 

I found this statement on the Booth Lake dam in an OPG document on the Madawaska Water Management Plan:

"The dam is located on the Opeongo River, between Lake Opeongo and Bark Lake. The original dam was built in approximately 1865 by a logging company. The dam was rebuilt in 1931 by another logging company. MNRF took over ownership of the dam in 1941. The current structure was built in 1958. The Booth Lake Dam is 4.0 m high by 60.4 m long with four log sluices. Each of the log sluices are 4.3 m long with a sill elevation of 28.0 or 27.7 m LD. A water level gauge is not installed at the dam. The Booth Lake log sluices have not been operated in over 30 years. Logs are permanently set in the sluices and the dam acts as a weir. The unchanged log setting allows for both stable recreational levels and the maintenance of the Booth Lake Bog along McCarthy Creek. "

https://www.opg.com/document/madawaska-river-water-management-plan/

From that description it doesn't sound like Booth Lake is used for flood control at this time.