Cyclists atop the Lion's Park Berm ride above a drypond and drain (lower left) that would be employed to collect storm water in the event city storm sewers were clsoed to prevent flooding. Officials told the news on Thursday that expected river levels this week may not be high enough to warrant widespread activation of the system. -- News photo Collin Gallant, June 17, 2022
COLLIN GALLANTcgallant@medicinehatnews.com
Twitter: CollinGallant
The South Saskatchewan River could rise by seven feet when recent rains cause it to crest in Medicine Hat late Friday, but not enough to warrant a widespread response by city crews.
A new forecast from the Alberta Rivers Forecasting centre on Thursday morning acknowledged that rain in the Rocky Mountains and near Calgary was less than anticipated. It did however, issue a high-stream flow advisory downstream of the Bow and Oldman rivers to the provincial boundary, while levels on both those major rivers were receding.
Medicine Hat could see the level reach its highest point late Friday, with officials stating that might only affect several storm sewer outfalls and very low-laying parkland, but not the wider community.
“The elevation of the river is expected to come up, but not to a level that will cause us concern,” said municipal engineer Carlie Collier. “We do have some (outfalls) that are quite low, and during peaks in any year they might be under water.”
During the 2013 flood, the record high-stream flow and height of the river forced water onto residential streets through the storm sewer system, which typically carries rain water to the river.
In response, the city upgraded 75 storm outfalls with two-way valves that block off when pressure on the river side becomes too great.
Carlier said the valves operate independently and “only one or two” might be engaged if the river rises to expected levels this weekend.
“We’ll continue to monitor the situation,” she said. “It will give us an opportunity to see how they operate.”
An expected local peak in the 1,000 cubic metre per second range is about one-fifth the volume seen in 2013.
Levels at the Finlay Bridge monitoring station were just above 4 metres in height at 4 p.m. on Thursday, up 1.5 metres (or four feet six inches) from midnight on Tuesday morning when a marked increase began.
Sask preps
Officials in Saskatchewan are releasing water in the Gardiner Dam to prepare for rain that fell in western Alberta to make its way through Medicine Hat and beyond late this week.
The Water Security Agency of Saskatchewan said Tuesday it will monitor rain volumes in the South Saskatchewan River basin — which feeds the huge Lake Diefenbaker reservoir — this week, but had initially increased outflows to accommodate the new volume.
Levels in the lake north of Swift Current had been low this spring owing to a dry summer and fall in 2021 and recent winter. SWA officials said release could be increased to the weekend and an emergency spillway near the hydro electric dam is available. They warned residents to be aware for the potential of rapidly increasing river levels.
The agency was also monitoring the North Saskatchewan River system, which also saw heavy rain in Alberta, and which joins the South Saskatchewan near Prince Albert.
