Contained within the 2nd Edition (1915) of the Atlas of Canada is a map that shows the delineation of drainage basin. The total area drained is indicated in square miles for each basin, and drainage basins of the principal river systems of Canada, along with their areas. This includes the great oceanic drainage basins and the Hudson Bay basin. Only the Canadian drainage area is indicated on the map for basins that lie partly in the United States. There is also a table listing the lengths of major rivers in Canada and their principal tributaries. | Contained within the 1st Edition (1906) of the Atlas of Canada is a map that shows the delineation of drainage basins. The geographic extent of each drainage basin is delineated and the total area drained for each basin is provided in square miles. This includes the great oceanic drainage basin and the Hudson Bay basin. Only the Canadian drainage area is indicated on the map for basins that lie partly in the United States. There is also a table listing the lengths of major rivers of Canada and their principal tributaries. | A drainage basin is an area that drains all precipitation received as a runoff or base flow (groundwater sources) into a particular river or set of rivers. Canada’s major drainage regions are the Atlantic Ocean, Hudson Bay, Arctic Ocean, Pacific Ocean and Gulf of Mexico. Rivers are organized into networks, each with its own recharge area upstream, and drainage channel and mouth downstream. Networks are ordered from ocean to main river to secondary rivers to streams which correspond to ocean basins, river basins, sub-basins, sub-sub-basins, and so forth. The boundary of a watershed is called a drainage divide. | Contained within the 4th Edition (1974) of the Atlas of Canada is a map that shows drainage basins as well as major lakes and diversions. The map displays the ocean drainage areas along with component river basins and diversion areas for the Arctic, Pacific, Hudson Bay and Atlantic drainage areas. | Contained within the 5th Edition (1978 to 1995) of the National Atlas of Canada is a map that shows ocean drainage areas with component river basins and diversion areas. There are two tables: one gives data on drainage basin areas, the other on major drainage diversions. | This map shows the five ocean drainage areas in Canada, the major river basins, the internal drainage areas and the diverted drainage areas. A drainage basin, sometimes called a watershed, is an area where all surface water shares the same drainage outlet. Surface water consists of the tiny trickles of water flowing on the surface of the earth that develop into larger streams and eventually combine to form a river. The boundary of a watershed is called a drainage divide.