Firefighters recovered about 80 pieces of rebar from the Bow River Tuesday after TransAlta used its Bearspaw Dam to lower the water level and give crews better access to the partially submerged scrap metal that had been snagging and puncturing recreational rafts.

Battalion Chief Alan Ball said firefighters cut and removed about seven dozen pieces of rebar that were attached to a few chunks of concrete at the bottom of the Bow. Crews were also building a boom to serve as a warning for rafters.

The Calgary Fire Department received nine separate calls for help over the weekend after rafts were caught up or damaged by the metal lurking just below the surface of the water in a shallow section of the river near Crowchild Trail.

It's believed the rebar may have been deposited in that location during the 2013 flood.

TransAlta said the river's flow would be lowered to 65 cubic metres per second by noon on Tuesday, down from its previous level of 109 cubic metres per second, to help firefighters get at the rebar and deal with the hazard.

Rafting down the Bow River is a popular summertime activity in Calgary, with hundreds of watercraft floating through the city on a given day.

The river levels should return to normal Wednesday, TransAlta said.