Overview of the prairie watersheds and aquifers
The rivers that flow across the prairies have their origin on the Eastern Slopes of the Rocky Mountains. The waters journey to the Arctic Ocean via the Mackenzie river system, the Hudson’s Bay via the Saskatchewan, Nelson and Churchill river systems and the Gulf of Mexico via the Missouri river system.
The Arctic Drainage Basin includes the Slave/Mackenzie, Peace and Athabasca Rivers. With an average volume of approximately 13, 400 m3/s (cubic meters per second) the basin drains 25% of the total area of Canada. By way of comparison, the average volume of Great Lakes/St. Lawrence river system is 10,100 m3/s. The Arctic Drainage Basin also contains the world’s 3rd, 4th and 8th largest natural lakes: Great Bear Lake, Great Slave Lake and Lake Athabasca respectively.
Present industrial activities are primarily located in the south of the basin and include pulp mills, oil and gas developments and the tar sands. Tar sands development has undergone extremely rapid expansion over the last 20 years and future development plans are under public scrutiny due to current and projected social and environmental impacts. New and proposed oil and gas developments - the Mackenzie Valley Pipeline in particular - pose the greatest threat to the integrity of the northern portion of the basin.
The Hudson Bay Drainage Basin includes the Theron, Dubawnt, Kazan, Churchill, Nelson, Red River/Lake Winnipeg, Assiniboine, Qu’appelle, Saskatchewan, North Saskatchewan, South Saskatchewan, Red Deer, Bow and Oldman River Basins. The Saskatchewan/Nelson system is the largest in the basin and drains 40% of three Prairie Provinces. The basin also includes a number of large lakes, including the Winnipeg, Winnepegosis, Manitoba, Reindeer and Diefenbaker (a man-made lake). Within the region, irrigation is the largest net consumptive user and hydro-electric energy generation is the largest non-consumptive user. Most of the Prairie population also lives within this basin, creating a substantial municipal water demand.
The two major rivers flowing through the Missouri Drainage Basin are the Milk and Frenchman Rivers. As with the other Southern Basin, irrigation is the major water user. Drought is very common in this dry area, which has led to the construction of many small and large storage facilities. An international agreement is in place to regulate both quality and quantity on both sides of the Canada-US border.
Groundwater research and policy is still in its infancy in Canada. Most aquifers, including those in the shared prairie watersheds, are still in the process of being mapped and evaluated. Although there is little documented information on the groundwater aquifers of the Prairie Provinces, allocations continue to be granted.
A permanent water deficit exists in areas of southern Alberta and Saskatchewan. In these areas, average water gain (through precipitation) does not equal water loss (through evaporation, transpiration and withdrawal). This water deficit has significant implications for groundwater use and allocation. Because surface and groundwater are connected, if surface water is over-allocated, groundwater recharge will decrease and availability will decline.
Cities such as Calgary and Lethbridge and industrial activities such as agriculture and the tar sands increasingly rely on groundwater availability for their water needs. In the absence of sufficient quantities and sustainable consumption practices they could run dry. Some areas have already outgrown available groundwater reserves. The town of Humboldt, Saskatchewan and the community of Lacombe/Panoka Alberta, for example, have been forced to build pipelines to divert water from the Saskatchewan River system to obtain water for their communities. The groundwater reserves they had relied upon to sustain their growing needs were no longer sufficient.
International scientists have begun to recommend that groundwater be viewed, in some areas, as a non-renewable resource. The Alberta basin, for example, contains deep groundwater reserves that are tens of thousands of years old. This means that it takes “ten thousand years for the water to recharge down into the very deep aquifer systems. If we extract this water, then we are removing what we would call fossil water and water that will take a very long time to recharge.”