Lower-than-normal snowpack and expected dry weather have prompted the City of Calgary to keep the Glenmore Reservoir at higher-than-normal levels this summer.
It was noted during this week’s discussion on the Status of Emergency Preparedness at the May 7 Emergency Management Committee meeting.
The conversation at the meeting had shifted to Calgary’s flood preparations for the upcoming year. Meanwhile, a briefing note on the 2025 disaster risk assessment summary showed a reduction in risk level for 1–100-year flooding on the Elbow River from high to low. New risks were added however, including 1-200-year flood risks for both the Bow and Elbow Rivers.
Though flood risks remain, there’s a growing focus on managing water in the case of potential drought. While the 2025 risk assessment dropped extreme hydrological drought from high to medium, preparations are being made to ensure Calgary has an appropriate water supply for the summer.
Frank Frigo, manager of environmental management in the climate and environment unit at the City of Calgary, confirmed that this year the Glenmore Reservoir with stay about two feet higher than normal summer levels.
Typically, the City of Calgary draws the Glenmore Reservoir down to prepare for spring runoff and rainfall, with May, June, and July accounting for 50 per cent of the city’s annual precipitation.
“Normally, what we would be doing with one more reservoir about this time of year is preparing for that double-factored component of the incremental runoff, the increased alpine snowmelt and the increased precipitation runoff from the heavier rains we see in May and June,” Frigo told LWC.
“This year, we’re seeing a little bit of a different pattern.”
Frigo said that in the Elbow River Basin, they’re seeing snowpack that’s in the 25th percentile. That means 75 per cent of the time they see considerably more snow in those feeder areas.
Driven by the Pacific Ocean
Long-term meteorological data from forecasters in Europe, Asia-Pacific and from Environment and Climate Change Canada (ECCC) show that Calgary will see lower than average precipitation this year, according to Frigo.
The forecasts are in line with what’s being seen in the Pacific Ocean, which drives the weather conditions seen in the Calgary area, Frigo said.
“Largely, the meteorological conditions we see in our part of the world are an artifact of the movement of heat around the Pacific Ocean,” he said.
“Not surprisingly, our models are showing us that we are likely to see lower than average precipitation this year. So that, in combination with the lower alpine snowpack that we’ve seen, are leading us to think really carefully about water management decisions, recognizing the total volume that will flow through our systems this year is likely to be lower than what it might be in a more average year.”
According to the Government of Alberta’s Water Supply Outlook for April 2025, 18 of 26 snow sites they surveyed were much below average, with six snow sites in the bottom five years of record. Bow snow sites were, on average, 47 mm less than last year, their report read.
It also shows the Bow River runoff volume forecast from April 1 to Sept. 30 to be below average, and much below average for the Elbow River.
They also included a long-range weather outlook from the National Oceanic and Atmospheric Administration (NOAA), showing a somewhat neutral forecast for precipitation and temperature. The ECCC forecast issued at the end of March suggested hotter, drier weather for southern Alberta.
“The April-May-June forecast probability of temperature product indicates a likelihood of above normal temperatures across most of Alberta with a high likelihood of above normal temperatures along the eastern slopes,” the Water Supply Outlook report read.”
No noticeable changes with the Glenmore Reservoir increase
The bump in water storage might seem small at two feet higher than normal. It equates to between one and two million cubic metres of water, or around 600 Olympic-sized swimming pools.
“When you think of it over the entire surface area of the Glenmore Reservoir, even a relatively benign depth of point five meters translates into a significant volume,” Frigo said.
“All of this is with the recognition that there’s continuous throughput.”
Frigo said the fluctuation in Glenmore depth, and the subsequent release of water to maintain certain levels, is all done with downstream impacts in mind. He said they are timing the releases so they’re not disruptive to the life phases of the flora and fauna along the Elbow River watershed.
In a typical year, there’s between four and five metres of water level variation in any given year. Most of that goes unnoticed by Glenmore Reservoir users, including any impacts to the docks used for recreation.
“Changing the water level by point five meters at this time of year is likely to be relatively imperceptible to virtually everyone, including recreational users,” Frigo said.
“Certainly, no significant impacts would occur in terms of how light penetration or the growth of vegetation within the reservoir might change or affect water quality. So, we don’t expect any impacts to water quality or other environmental outcomes with this, with this relatively modest adjustment in management practice.”
The City of Calgary will be in regular communication with other water users to monitor demand in the coming months. The increase in the Glenmore Reservoir water level is a pre-emptive measure, along with the use of the Bearspaw water treatment plant.
“That allows us to be very flexible in working with both systems to try and balance those environmental as well as water use needs,” Frigo said.
“Depending on how that would all work out, this will give us an incremental supply that would assist us for a period of additional weeks if we needed that incremental flow.”
