Almost 70 percent of water consumed in the province originates in the South and North Saskatchewan and Qu'Appelle river systems. Water from Lake Diefenbaker, in the South Saskatchewan system, supplies about 90 percent of the flow in the Qu'Appelle River in low flow years. Buffalo Pound Lake, along the Upper Qu'Appelle, supplies water to the cities of Moose Jaw and Regina.
Climate change is threatening the future of the South Saskatchewan River-one of Saskatchewan's most important physical assets. Overwhelming evidence indicates the climate of the Prairie Provinces is warming and drying, resulting in decreased river flows. If climate change continues to accelerate as predicted, water will be in short supply for municipalities, industry and recreational users in the coming decades.
As river flow is decreasing, water use is increasing. Canada uses more water per person than any other nation except the United States. Between 1972 and 1991, water use per person increased by 50 percent. And as the climate gets hotter and drier, the demand for water can only increase. When increased demand is combined with reduced supply, water availability becomes a critical issue.
While it may seem that there is plenty of water in the South Saskatchewan system, there are also many users competing for it. In Saskatoon, for example, people use an average of 230 litres per day, which translates into a municipal withdrawal of approximately 40 million cubic metres a year. Flows through Saskatoon averaged 50-55 cubic metres per second during the summer of 2001, dangerously close to the minimum of 42 cubic metres per second required to operate the municipal water system.
Of course, Saskatoon is just one of many water users spread throughout a river basin that runs across three provinces. Even Regina, which is not located in the Saskatchewan River basin, relies on water diverted from Lake Diefenbaker on the South Saskatchewan.
A formal arrangement between the three Prairie Provinces, called the Master Agreement on Apportionment, governs the sharing of water in the Saskatchewan-Nelson watershed. According to the agreement, Alberta guarantees 50 percent of the natural water flow in the river system to downstream Saskatchewan, and Saskatchewan does the same for downstream Manitoba. But what will happen to this agreement in a much drier and hotter world?
The agreement is already being put to the test. Alberta irrigates 500,000 hectares of farmland from the Saskatchewan system. In 2000, diversions form the Bow River for irrigation took over 95 percent of the river's flow on some days, causing significant fish kills. In 2001, irrigation allocations were reduced by 50 percent, but how will the Alberta government respond in the future to extreme drought conditions? Will it honour its water commitments under any circumstances? And will Saskatchewan honour its commitments to Manitoba?
Lower river flows could be a source of political tensions, since many crucial services depend on a reliable supply of water. SaskPower, for example, has several hydroelectric plants on the Saskatchewan system. Will power supplies be affected by consecutive droughts? What impacts would there be on irrigation or on municipal water supplies?
Treated sewage and untreated storm water are disposed into the Saskatchewan system by many communities, including Saskatoon. Waste disposal still depends to a large extent on dilution; lower water flows will mean less dilution, which could have a substantial impact on downstream water quality.