List of longest rivers of Canada
Nine rivers in this list cross international boundaries or form them. Four—the Yukon, Columbia, Porcupine, and Kootenay—begin in Canada and flow into the United States. Five—the Milk, Pend d'Oreille, Saint Lawrence, Red, and Saint John—begin in the United States and flow into Canada. Of these, the Milk and the Kootenay cross the international border twice, the Milk leaving and then re-entering the United States, the Kootenay leaving and then re-entering Canada. The drainage basins of these nine rivers extend into both countries; in addition, the drainage basins of six others—the Fraser, Assiniboine, South Saskatchewan, Saskatchewan, Nelson, and Winnipeg—extend into the United States even though their main stems flow entirely within Canada.
Technological and industrial history of 21st-century Canada
Geological formations of shale gas are being explored as a new source of energy. A technique known as horizontal drilling is used to create a horizontal bore hole, through a formation. Water under high pressure is then pumped into the bore hole where it fractures the shale and allows the gas to escape the rock and seep up the bore hole. There are a number of shale gas fields in Canada including the Shallow Colorado basin in Alberta, Saskatchewan and Manitoba, the Bakken, in Saskatchewan and Manitoba, the Antrim in Southern Ontario and the Utica in south east Quebec. The technique is not without problems for the fracturing can affect aquifers causing contamination and deviation. To date efforts at production in Canada have been limited to exploratory wells.