FORT MACLEOD, Alta. – As rain and snow patterns change, the result is lower prairie river flows.
Rainfall and snow pack levels vary each year but research into the timing and amount of precipitation in the mountains shows it has declined since 1900 when records were first gathered.
In the last century the South Saskatchewan River basin water supply dropped about 20 percent, said Stewart Rood, environmental scientist and expert in river resources management at the University of Lethbridge.
“This is important because a lot of our policies and even some allocations such as ‘first in time, first in right’ were established a century ago under a different set of hydrologic conditions,” he told the annual meeting of the Oldman River basin council in Fort Macleod.
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Glaciers are also receding but they are not the main water source for Alberta rivers.
“Climate change is not new and glacial recession is not new, but it has been accelerating over the past few decades,” he said.
Snow melt is the major contributor to river runoff.
Predicting future weather patterns and water availability has been based on analyzing past weather and using computer generated models. New modeling research indicates higher winter river flows and substantially lower river flows during the summer when the demand is highest for water.
Climate change is responsible for fewer cold winters in the Rocky Mountains so rain is coming when snow should be falling.
There is a trend to less snow so scientists anticipate stream flows in August and September will drop because there is less deep mountain snow available to melt.
Researchers at the universities of Lethbridge and Saskatchewan, provincial governments and the Red Deer River alliance have analyzed this information using new computer predicting systems. They forecast more extreme weather variation and differences in river flows by 2055.
The Oldman River water volume is likely to remain about the same, but the Bow and Red Deer rivers can anticipate higher winter flows and less water in the summer.
The model does not include variables like land use change such as loss of forests due to logging, mountain pine beetle outbreaks or fire.
In past years water management has included building dams and reservoirs to capture excess water, Rood said.
“I do not recommend building more dams but with the ones we’ve already got, let’s use them for both economic and environmental uses.”
In 1988, the Oldman River system ran dry because of a low snow pack, little rain and 90 percent of the available water being diverted for irrigation or storage.
The Oldman River dam project was announced after that drought, and while controversial, it has helped control the river by capturing sufficient spring flow for later use.
More changes have come in dam management especially after the southern Alberta flood of 1995.
Engineers use “flow ramping” where water is released at a rate more in line with what nature would do under certain flood conditions.
This technique did not do much to improve the St. Mary’s system, but the Waterton River dam and Oldman dam release water in such a way that shorelines and floodplains are improving. This is noted in the regrowth of cottonwood trees in riparian zones.
