By David Schindler
Posted on March 1, 2006
Canadians are always told by our politicians and media that we have abundant supplies of fresh water from our lakes and rivers. But the statistics do not bear this out. The true measure of water that we can use sustainably is the annual runoff from land. If we exceed that value, our water use is unsustainable. Canada has seven percent of the world’s land mass, and produces seven percent of the world’s terrestrial runoff. In other words, we have just an average supply of sustainable freshwater by global standards. Another common myth is that we have more water than the USA. Again, the numbers dispel the myth. The runoff per unit area in the two countries is almost identical.
One reason for the apparent abundance of our freshwaters is that we have abundant places for water to collect—in the depressions left by receding glaciers several thousand years ago. But having more basins to catch rain does not mean that more rain falls! Much of northern Canada, where freshwater is most abundant, receives less than 250 millimetres of precipitation per year. Many of the larger lakes would require 100 years or more to refill if we emptied them.
We also often forget how much of our water is in inconvenient places. Most Canadian rivers flow northward, away from the 300-kilometre-wide band along the U.S. border where most of Canada’s 30 million people reside, and where most of our demand for water occurs.
The western prairie provinces (Alberta, Saskatchewan and western Manitoba) are the driest part of southern Canada. In the rain shadow of the Rocky Mountains, some parts receive an average of less than 350 mm of precipitation per year, less than average evaporation. The only reason that agriculture and large cities like Calgary have been able to thrive is because their shortage of precipitation has been offset by rivers and aquifers draining from the Rocky Mountains, where higher precipitation and melting glaciers supply much of the water, especially in the dry summer months when water demand on the prairies is highest.
Both historical accounts and paleoecological studies reveal that these provinces have been plagued with droughts for centuries. In fact, the 20th century—when European immigrants arrived to begin instrumental measurements—appears to have been the wettest century of at least the past two millennia. Even the “dirty ’30s” suffered only a puny drought by long-term standards. Many droughts in earlier centuries lasted 20 years and more.
The probability that the 21st century will be as wet as the 20th seems very small. Furthermore, the effects of climate warming will aggravate the freshwater problem, if droughts occur. Already, parts of the western prairie provinces have had temperature increases of two to four degrees Celsius.
Another two to three degree increase is projected to occur by mid-century. Climate models also predict slight increases in precipitation. But the predicted increases would not be enough to counteract the increases in evaporation caused by increased temperatures. For the past 30 years, snowpacks have been getting smaller and melting earlier. The major glaciers of the eastern slopes have lost 25 to 37 percent of their mass in the past century. In nearby Glacier National Park in Montana, glaciers are predicted to disappear within 25 years. In short, glaciers and snowpacks will continue to dwindle, and they will not return.
It is perhaps ironic that Alberta, the province most vociferously opposed to controlling greenhouse gases in order to protect its pampered petrochemical industries, will almost certainly be the first to suffer from freshwater shortages. Some communities are already short of water. River flows in summer are only 40 to 70 percent of historical values. Seventy percent of irrigated agriculture in Canada takes place in Alberta. The province has the fastest population and industrial growth in Canada. There are only about 200 fish-bearing lakes in the province, and many of these are suffering already from poor water quality, the result of extensive land clearing, wetland destruction, growth of human and livestock populations, cottage development, and collapse of fisheries.
To a water expert, looking ahead is like the view from a locomotive, 10 seconds before the train wreck. Sometime in the coming century, the increasing human demand for water, the increasing scarcity of water due to climate warming, and one of the long droughts of past centuries will collide, and Albertans will learn first-hand what water scarcity is all about. Water scarcity will become one of the most important economic and environmental issues of the 21st century in the western prairie provinces.
But there is much that we can do to manage the problem. An average Canadian consumes about 326 litres of water per day at home, about twice the per-capita water use of Europeans, and many times that of people in Middle Eastern countries. Metering water and punishing high-water use with high cost would be a good start. The options already used in water-scarce parts of the USA could be copied—Xeriscaped lawns, low-water toilets, low-flow shower heads, reuse of gray water for lawns and gardens, and many other such practices.