A new study says rules governing how much water oilsands plants can take from the Athabasca River aren't based on enough information and don't account for how low flows can get in the crucial waterway.
It's the second recent paper that questions assumptions about water use in the region and comes after withdrawal permits from the river were suspended due to low levels.
"There's much more variability than what we've experienced, or than what we've measured,'' said David Sauchyn of the University of Regina, whose paper was published Monday in the Proceedings of the National Academy of Sciences.
Sauchyn said allocations from the Athabasca have been based on flow data from monitoring stations set up in the river. He points out that data only goes back a few decades and that good, consistent information doesn't exist before the 1950s.
Official statistics don't even include the drought of the 1930s, one of the driest periods in the historical record.
Sauchyn and his colleagues used a scientifically well-established method of using tree rings to estimate water flows going back 900 years. They found the river level has fluctuated much more widely than the last 62 years of records suggest.
Although the Athabasca's flow rate has never had a yearly average of less than 200 cubic metres per second during the recorded period, Sauchyn found it has dropped below that level 36 times since about 1100 AD.
The 200-level translates into a winter flow of about 46 cubic metres per second. Over the next decade, the Alberta government estimates oilsands demand will grow to 16 metres per second, meaning industry could be removing more than a third of the river's entire winter flow.
Sauchyn also found that low-flow periods sometimes lasted more than a decade.
"We've been able to withstand single-year droughts pretty well,'' he said. "But if it gets to three, five, 10, 20, like we saw in the past, that is a much more challenging scenario.''
The study also exposed the role of long-term, large-scale climate cycles in the Athabasca's flow.
North America is currently in the wet phase of a 60-year cycle. When the dry phase returns, it will do so with the Athabasca already experiencing declining average flows.
"It'll compound the problem. It's a double whammy.''
Sauchyn's paper follows one in August that concluded climate change will further decrease flows in the Athabasca by reducing the amount of water stored as snow in the river's headwaters.
That paper in the publication Climate Change suggested that by mid-century — well within the expected lifespan of most oilsands developments — low water levels leading to withdrawal disruptions could increase by up to 40 per cent.
That study was released the same week Alberta's energy regulator cancelled 72 industrial temporary water withdrawal permits for the Athabasca. The regulator cited water levels that were 43 per cent below normal.
Industry is taking steps to reduce its dependence on the Athabasca. Oilsands producers have committed to cut water use by 30 per cent by 2022. Some facilities store water on site for use when flows are low.
Sauchyn said his research applies to allocations of water from other rivers as well.
His study was funded by Environment Canada with the endorsement of Canada's Oilsands Innovation Alliance, an industry group that seeks to share research. The alliance has been given a copy of his work.
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