A creek bed that should be full of water is just a tiny stream near Vulcan, Alta., on April 23. (Todd Korol/Reuters)

Southern Canada lost more than 1.4 million Olympic-sized swimming pools' worth of fresh water annually between 1971 and 2004, an overall loss of nearly nine per cent, a newly released study shows.

Overall, the freshwater supply fell by an average 3.5 cubic kilometres a year during those 34 years, a drop of 8.5 per cent, the Statistics Canada study found. The total annual renewable freshwater supply for Southern Canada, where about 98 per cent of the population lives, is about 1,326 cubic kilometres, compared to 3,470 for Canada as a whole.

Freshwater supply is represented by water yield, the results of precipitation and melted ice that flow over and under the ground and eventually reach rivers and lakes, Statistics Canada said.

Canada's industrial sector relies heavily on renewable freshwater resources. In 2005, more than 90 per cent of the fresh water being used went to the following sectors, in order: thermal-electric power generation, manufacturing and agricultural. The residential sector used just nine per cent.

The Prairies — the southern parts of Alberta, Saskatchewan and Manitoba — had the lowest and least predictable water yield between 1971 and 2004, the study found. At the same time, demand for water presumably increased, because the region's population rose by 1.6 million, to 4.5 million people.

"This variability is of interest because a lack of predictability in the flows of renewable water resources affects economic activities, including agriculture," the study said.

Water yield typically comes mostly in the spring and declines greatly through summer months, when demand is highest.

The Prairies' water yield was just 12 per cent of that of the Great Lakes drainage region and just six per cent of the Maritime coastal drainage region's. The amount of renewable fresh water per unit was also less than that of either of Australia or South Africa, the study said.