Canadian Drainage Areas
The Major Drainage Areas (MDA), as portrayed in this map, are part of the Standard Drainage Area Classification (SDAC) which was developed by Natural Resources Canada, in partnership with Statistics Canada, and Environment and Climate Change Canada.
The 11 MDAs presented in this map comprise the uppermost level in the drainage area classification system which then divides into 164 sub-drainage areas, and then is further divided into 974 sub-sub-drainage areas. A drainage area, as opposed to a drainage basin or watershed, is a unit of statistical aggregation used for reporting purposes based upon drainage patterns and the underlying basins, delimited by a drainage divide.
Relief was derived from the merging of two raster data sets, both resampled to 804 metre resolution: