Ottawa River drainage basin
The Ottawa River drainage basin is the drainage basin in northern North America where surface water empties into the Ottawa River and adjoining waters. Spanning an area of about , it is the 12th largest drainage basin in Canada, occupying the Canadian provinces of Ontario and Quebec. It accounts for about 11% of the total Saint Lawrence River drainage area.
Water supply and sanitation in Canada
Metro Vancouver's water system is one of the largest in North America. Almost 600 square kilometers of mountainous land is closed to public access to protect the large reservoirs which collect rain and snow melt. 
Three watersheds - the Capilano, Seymour and Coquitlam Watersheds are the water source for more than two million residents in the most populated urban region of British Columbia. Each watershed supplies about one-third of the region’s tap water. The regional district’s long-standing closed watershed policy is one component of a water supply system that provides multiple barriers to contamination, from source to tap.