The Ottawa River forms the border between Ontario and Quebec, and for the last 150 miles of its 790 mile length has more flow than Europe’s Rhine.  It’s a pool and drop river either naturally or from large dams, so it’s both river and lake, with huge lakes and also several areas of very dangerous whitewater, with winds capable of raising flat water to whitecaps in 20 seconds in many lengths of the river because of it’s general east-west run.  The water quality is generally good above Renfrew, Ontario, but poor below, although huge Muskie live in the river south-east of Ottawa.  The Quebec side of the river can be virtually uninhabited for long stretches, 3 habitations in one 50 mile stretch for instance, and the Ontario side can be very wild as well, with total seclusion easily found.  My favourite part of the Ottawa is the Quebec side across from the Ontario town of Deep River, where for about 40 miles you find beautiful sand beaches equipped with picnic tables and outhouses, free camping, pure springs of water (especially at scenic-historic site Oiseau Rock five miles east of Deep River.)  Long holiday weekends are not the time to visit though, as powerboaters take over the beaches, and noise is unbearable.  the Ottawa is gateway to many wild and scenic major rivers and special areas .. the Mattawa-French rivers being the ancient canoe route linking Montreal to the upper Great Lakes, and Hudson Bay accessible from near the Ottawa’s source.  Water quality is even better above the town of Mattawa, Ontario.  Portaging around power dams can be a long affair of a few miles, but I have always found a local person happy to help with a pickup truck, and always for free as they enjoy becoming part of a long distance canoe adventure.  I’ve paddled the ‘Voyageur’ route twice solo, and have not had to pay for camping on either of those trips of about 750 miles each, and have only been refused permission to camp on one island .. there is always another spot.  There is plenty of real wilderness, but also many villages and towns for resupply.