Drainage contributing to flooding in western Canada, expert says

Bruce Johnstone in the Leader Post (Regina): An expert on hydrology and climate change believes the recent flooding in Saskatchewan and Manitoba has been exacerbated by the widespread drainage of agricultural lands that have increased water volumes that flow downstream into Manitoba. “The short answer is, yes I do,’’ said John Pomeroy, Canada research chair in water resources and climate change and director of the Centre for Hydrology at the University of Saskatchewan.

Pomeroy, who has studied water volumes on the Smith Creek watershed over the last 55 years, says agricultural drainage of sloughs and other wetlands appears to have been one of the factors in the recent flooding. “The volume of streamflow is basically doubled from what it was if the wetlands had stayed intact in 1958,’’ Pomeroy said. “It looks like the peak flows have increased about 30 per cent from that.’’

Pomeroy said the Churchbridge-Langenburg area has seen it wetlands reduced from 25 per cent in 1958 to 10 per cent in recent years. “There’s been a lot of drainage there ... It gives us some idea of the impact of drainage in a lot of the Assiniboine (River system),’’ Pomeroy added.

Pomeroy said the floods in 2011 and 2014 have seen the confluence of several factors, including multiple days of persistent rainfall in summer, while previous floods were due to excessive snowmelt in the spring.

“This is what’s making it a perfect storm," Pomeroy said. “There’s been a lot of difficulty in estimating the flood peaks because things like this (agricultural drainage) are making older observations more difficult to interpret. So we’re seeing something that is — it’s a cliché to call it climate change — but that’s exactly what this is.”

And he believes the Saskatchewan government should be doing what the Manitoba government has done by bringing in stiff penalties for illegally draining farmland. “Manitoba made it (unauthorized agricultural drainage) against the law on June 10 with really strict regulations and big fines.’...’

A 2011 flood on the Red River in Winnipeg, shot by Shahnoor Habib Munmun, Wikimedia Commons via Flickr, under the Creative Commons Attribution 2.0 Generic license