Incoming Alberta rains good for farmers, unlikely to cause major flooding, says meteorologist

Alberta's seasonal 'June monsoon' is expected to be kicked into high gear Monday afternoon, with Environment Canada issuing warnings for heavy rainfall across much of the southern part of the province, including Banff National Park, Kananaskis and Calgary. 

In a warning issued by Environment Canada Monday morning, the agency says prolonged and significant rainfall event will bring 75 to 125 mm of rain by Wednesday morning in the Calgary area. 

Rainfall warnings are also in effect for Banff, Canmore, Kananaskis, Red Deer, Nordegg, Rocky Mountain House, Airdrie, Cochrane, Olds, Sundre, Okotoks, High River and Claresholm.

Kyle Brittain, the Alberta bureau chief for the Weather Network, said that while this week's prolonged rainfall could put the province past its typical monthly average for June, he doesn't expect it to cause severe flooding.

That's because historical dry conditions across the southern part of the province have led to a lower than average water table, said Brittain, leaving substantial room in the ground for moisture to be absorbed.

"[The] exceptional drought in southern Alberta, that actually gives us quite a good buffer against major flooding right now."

For Alberta farmers fearful that another drought like last year's could be repeated, Brittain said the heavy rainfall will bring some reassurance. 

"It looks like it's going to be a million-dollar rain for agricultural producers in southern Alberta. So it could actually really turn things around for our growing season."

Conditions which led to major flooding in parts of the province in 2013 were caused by both a higher amount of rainfall (over 300 mm in parts of the province) and concurrent storms close together, said Brittain. 

"If we have another big storm after this one, then we've got to start looking at flood concerns."

For now, Brittain said to expect some swollen rivers, with high water levels coming into Calgary from both the Bow and Elbow rivers. 

City making preparations

On Sunday, the City of Calgary issued a boating advisory for the Elbow River, due to higher expected flow rates. According to the statement, Calgarians are advised against boating and all other watercraft activities on the Elbow River until conditions improve.

Frank Frigo, manager of watershed planning with the city's water resources department, said it's preparing for the extended rainfall by lowering water levels at upstream reservoirs on the Bow River and at the Glenmore Reservoir to increase storage capacity in case of high flows.

While the city said it doesn't expect major flooding, it advised that Calgarians should still take precautions including directing rainwater away from homes by properly positioning downspouts, moving valuables out of basements in low-lying communities and exercising caution around riverbanks, especially on riverside pathways. 

According to city council's Emergency Management Committee, flood mitigation efforts in Calgary as of 2022 have reduced future potential flood damages by 55 per cent, or an average of $90 million per year.

These include upgrades to the Glenmore Dam, the implementation of flood barriers, around the clock monitoring of weather and river conditions and increased community outreach regarding flood preparedness.

Frigo said these measures, in addition to the city's investments into more extensive weather modelling programs, have equipped it to better withstand more extreme weather events. 

"We do have much better tools to be able to try and interrogate, look into the future and understand the range of possibilities." 

Snowpack precautions

Higher than average snowpack levels for this time of year across the Rocky Mountains — due to heavy winter snowfall and a fairly cool spring — have also given rise to concerns of flooding caused by melting snow.

But John Pomeroy, director of the global water futures programme out of the University of Saskatchewan, told CBC News he doesn't expect incoming rains to exacerbate conditions drastically. 

"It takes a heavy rainfall event to occur with the snow melt to really trigger the size of flooding that we had in 2013," said Pomeroy. 

"We do have some heavy rains [forecasted] … that will cause some high flows for sure. But it doesn't look at all like the kind of flooding that we would have seen in 2013." 

Pomeroy said the large amounts of accumulated snow in the mountains mean people should be on high alert for avalanches, and advised recreational users to avoid river-related activities at this time.

"Water's coming in at zero degrees Celsius into the river and it's going to be fast [moving]. So [plan] your trips very, very carefully and expect rapid change at this time of year."