The water levels in the great lakes and St. Lawrence River system are regulated by a joint commission from Canada and USA, not by Quebec. The water level is a problem for all jurisdictions. The Island of Montreal is also experiencing high water and some flooding right now. If the open the gates to quickly, there will be disastrous results down stream. The problem is just too much rain in a short period of time. It is a tough balancing act controlling the water levels  in the lakes, river and seaway.