The Mackenzie River system, 4241 km long (to head of the Finlay River), is the second largest in North America (after the Mississippi River).
The Mackenzie River system, 4241 km long (to head of the Finlay River), is the second largest in North America (after the Mississippi River). Its total drainage basin of 1.8 million km2 is the largest of any river in Canada and its mean discharge of 9700 m3/s is second only to that of the St Lawrence. The river's peak discharge occurs in June, but its flow is generally uniform because of the flat Barren Lands east of the river and the many large lakes in the system. The lakes and rivers of the Mackenzie and its tributaries are open from mid-June to the beginning of November in the northerly areas.
The river's sparsely populated basin is one of the few great unspoiled areas of the world. The main headwaters are the Peace River and the Athabasca River, while the main stream (1738 km) issues from the shallow swamps and mudbanks of the West Arm of Great Slave Lake. It flows west to Fort Providence, where scows, canoes and York boats were hauled upstream. At Fort Simpson the Liard River reaches the south bank of the Mackenzie, which receives its muddy waters. Near the North Nahanni River the Mackenzie trends west-northwest through a rolling plain and deflects north past an escarpment of the Mackenzie Mountains, which lie parallel to the river. The Redstone and Keele rivers and other streams cut through the mountains and pour into the lowlands through deep canyons.
At Tulita the clear, cobalt waters of the Great Bear River enter over a shallow gravel bar. Past Norman Wells the Mackenzie continues through weedy channels and beneath ribbed cliffs, widening to 5 km, its path braided among countless islands. At Sans Sault Rapids a rocky promontory juts into midstream, and rough water endangers navigation. A few kilometres above Fort Good Hope the river widens and constricts again, between limestone cliffs called The Ramparts, then resumes its meandering northwest, its channels clogged with islands and shifting sandbars. The Arctic Red River enters 270 km from the sea, and at Point Separation the delta begins.
The Mackenzie Delta is a vast fan of low-lying alluvial islands, covered with black spruce, thinning northward. These trees are large enough to be used for construction of log buildings and are widely used as fuel. The delta is a maze of channels, cutoff lakes and circular ponds, which are home to a large muskrat population. The delta is 80 km across, bordered by the Richardson Mountains in the west and the Caribou Hills in the east. Below Point Separation the river splits into 3 main, navigable channels: East Channel, which flows past Inuvik on the easterly edge of the delta; Peel Channel in the west, which flows past Aklavik; and Middle Channel, which carries the main outflow into the Beaufort Sea. Tuktoyaktuk, northeast of the delta, is the transfer point for river and ocean cargo; its harbour is open from July to late September.
The Mackenzie River Lowland is a great northward extension of the central plains. On the west side rise the Mackenzie Mountains, and on the eastern edge lie the rocky outcrops of the Canadian Shield. The valley is underlain by sedimentary rock, but its surface is mostly glacial gravel, sand and clay. The plains of Muskeg are broken by stunted spruce and fir, bog, swamp and lakes. Much of the terrain is underlain by permafrost, which presents a challenge to construction of buildings and transportation.
In 1778 Peter Pond traversed Methye Portage (Portage La Loche), connecting the fur trade routes of Hudson Bay with the Mackenzie Basin. Alexander Mackenzie came in 1789, following the full length of the river aptly named for him. Other traders followed, establishing posts along the way. From the 1820s supplies were carried by York boats. The first steamer plied the Athabasca River in 1884, and in 1886 operated north of Fort Smith. From 1920 to 1940 flat-bottomed sternwheelers plied the river, but after 1945 they were replaced by tugs and barges. The tugs are now equipped with radar and depth sounders.
The lowland is still sparsely populated. The fur-trade economy dominated until the mining rushes of Yellowknife and Great Bear Lake and the Canol Pipeline of WWII. Fur remains important to the local residents; mining has been dominant, although its fortunes fluctuated in the latter part of the 20th century. Most mining has been concentrated in the Shield. Today the key mining centres are Yellowknife (gold), Norman Wells (oil and natural gas) and Fort McMurray (tar sands). In the past there was mining along Great Bear Lake at Echo Bay - formerly Port Radium - and Lake Athabasca, at Uranium City (uranium); and along the Flat River at Tungsten (tungsten). Large natural gas deposits have also been found near Fort Liard on the Liard River and in the Mackenzie Delta. The fine clay soil would support agriculture, but climate prevents it. Waterpower sites are on the Snare, Talston and Yellowknife rivers, which all flow into Great Slave Lake, and on the Peace River near its headwaters. The river and the delicate environment of the North were brought to the national consciousness during the debate over the Mackenzie Valley Pipeline.