Mackenzie River
At , the Mackenzie River drainage basin encompasses nearly 20 percent of Canada. About , or 54 percent of the basin, lies above Great Slave Lake. Permafrost underlies about three-quarters of the watershed, reaching up to deep in the Mackenzie Delta. As a whole, the Mackenzie basin receives only meager to moderate rainfall, averaging over the entire basin, though mountain areas experience much higher precipitation, and areas near and north of the Arctic Circle receive much lower precipitation.
Petitcodiac River
Six species have disappeared from the river since the mid-1980s. The Petitcodiac River was the only known Canadian habitat of the dwarf wedgemussel, and was later isolated to just nine American watersheds after its elimination from the Petitcodiac. The Atlantic salmon is no longer present in the watershed, and has since been listed as an endangered species in Canada. The American shad was a favourite with fishermen, and represented two-thirds of the entire Canadian shad landings from 1870 to 1900; catches peaked at  million kilograms (two to six million pounds) per year. Three other species have been eliminated from the river: the striped bass, the Atlantic sturgeon, and the Atlantic tomcod. However, a project of the Petitcodiac Riverkeeper, funded by the Government of Canada's Environmental Damage Fund in 2005, noted that the removal of the causeway would result in a "good" chance of bringing back the eliminated species, and an "excellent" chance of increasing the numbers of species deemed to have been reduced in numbers. No data has been released for the Atlantic salmon or the striped bass.