Page "Mackenzie River" Paragraph 8

With an average annual flow of, the Mackenzie River has the highest discharge of any river in Canada and is the fourteenth largest in the world in this respect.

About 60 % of the water comes from the western half of the basin, which includes the Rocky, Selwyn, and Mackenzie mountain ranges out of which spring major tributaries such as the Peace and Liard Rivers, which contribute 23 % and 27 % of the total flow, respectively.

In contrast the eastern half, despite being dominated by marshland and large lakes, provides only about 25 % of the Mackenzie's discharge.

During peak flow in the spring, the difference in discharge between the two halves of the watershed becomes even more marked.

While large amounts of snow and glacial melt dramatically drive up water levels in the Mackenzie's western tributaries, large lakes in the eastern basin retard springtime discharges.

Breakup of ice jams caused by sudden rises in temperature – a phenomenon especially pronounced on the Mackenzie – further exacerbate flood peaks.

In full flood, the Peace River can carry so much water that it inundates its delta and backs upstream into Lake Athabasca, and the excess water can only flow out after the Peace has receded.