When Ednie’s field season wraps up in the fall, he returns home to his family in Chelsea, Que., within cycling distance of the Geological Survey of Canada’s Ottawa office. There, he sits at the computer and crunches data to find a number called “mass balance” — the difference between the mass added to a glacier in winter (through snowfall, avalanches, windblown snow) and all the mass lost in summer (through ice and snowmelt or calving, when large chunks of ice become detached). A negative mass balance indicates the glacier is losing mass. It’s dying.

“Peyto has been losing mass at an increasing rate since 2015,” Ednie says.

Imagine a healthy glacier as a river of viscous glue moving downhill so slowly as to be imperceptible. The upper basin of a glacier is known as the zone of accumulation. Snow falls throughout the winter, and over the next year becomes “firn,” a type of partially compressed snow. Firn accumulates and is eventually compressed into new ice. These days, many mountain glaciers are melting to bare ice from the top to the terminus. There is no new ice formation, just loss.

For the Peyto, 2023 was a scorcher. That year, Ednie calculated a mass balance of -2,760 millimetres of water. That’s equivalent to 25 million tonnes of water, or enough liquid to fill 1,000 Olympic-sized swimming pools that poured off the glacier into the North Saskatchewan River basin.

After a full day of fieldwork, Ednie’s and Smith’s shoulders ache from drilling holes in ice. The Catharine and Peter Whyte Hut beckons from a boulder ridge below Mount Thompson. They traverse the glacier past crevasses, natural cracks that form as the ice bends and folds under the pull of gravity. Vertical blue-green walls of ice disappear into blackness.

They find a ramp of smooth ice that exits the glacier onto polished bedrock. So recent is the glacial retreat here that oxidization has not yet darkened the rock, and no lichen is growing on its surface. They remove their crampons and hike up the slope, searching for solid footing in a shifting landscape of loose talus. When the team pull off their boots, it’s time to crack happy hour beers on the hut’s deck. Rockfall suddenly cracks like a pistol shot from crumbling Mount Habel, which has been shedding onto the Peyto’s upper slopes all summer. Then it’s silent again, except for the omnipresent rush of moving water.

Pomeroy heads a team of technicians and graduate students who manage the Canadian Rockies Hydrological Observatory, a network of more than 40 hydrometeorological stations across a swath of rugged mountain country from the Columbia Icefields south to Kananaskis Country. Using radio telemetry, the stations beam real-time data on precipitation, wind, temperature and humidity to the Coldwater Lab. The goal is to uncover what is happening in mountain hydrology — and how that is affecting “exotic rivers,” which deliver moisture from high-humidity regions to dry areas where rivers may be the only reliable source of water. The Bow and North Saskatchewan serve that function for the Canadian Prairies.

When people think of the Canadian Rockies, they imagine iconic glaciers tumbling from mountain peaks toward turquoise lakes. Glaciers are sexy. People love taking photos of them. It’s the reason the United Nations declared 2025 the International Year of Glaciers’ Preservation, a hopeful name intended to galvanize public awareness about the rapid global warming-induced changes in the cryosphere.

Yet despite the thundering cascades of water spewing from glaciers on a hot summer day, ice melt contributes a surprisingly small percentage to the overall flow of mountain rivers. For the Bow River, says Pomeroy, that’s anywhere between three and five per cent. But glacial melt is still an important pulse of cold fresh water that comes at the hottest time of year.

Computing the shifting variables of the mountain hydrology equation — rainfall, snowpack, glacier recession, temperature — and making future predictions about weather is not an exact science. It’s more like a hydrological Rubik’s Cube.

When he and his team sampled material scraped from the glacier’s surface they discovered a toxic cocktail of algae, viruses, bacteria, fungi, dust, soot and industrial pollutants from diesel, gas and rubber tires.

“That’s not something I’d want to drink,’’ Pomeroy says.

Across the valley from the Coldwater Lab, Cathy Ryan, a University of Calgary hydrogeologist, dips her foot into the Bow River. It’s bone-achingly cold, even on a hot summer day. Ryan calls herself a “groundwater chauvinist.” Photogenic glaciers sell themselves. Groundwater doesn’t. It’s why she believes the importance of glaciers is sometimes overemphasized, while that of groundwater is often overlooked in the mountain hydrology equation.

A keen eye can see evidence of groundwater throughout the Rockies. Ryan points to the sheer northeast face of Mount Rundle, a fortress of sedimentary rock that stretches for about 10 kilometres between Canmore and Banff. Rundle is a textbook example of what geomorphologists playfully call the “Paleozoic sandwich.” The mountain exhibits three distinct layers. Hard cliff-forming Palliser limestone is on the bottom, and equally tough Rundle Group limestone is on the top. Sandwiched in between is a weak and crumbly layer of Banff shale from which water drips and cascades. Climbers love it. In winter, some of the most famous ice climbing routes in the Canadian Rockies, like Professor Falls and Sea of Vapours, form from frozen wisps of ice dripping like candle wax from the porous middle of this geologic layer cake.

Farther south in the Livingstone Range, rancher John Smith pulls into “cowboy camp” in a pickup truck towing a loaded cargo trailer. He rolls to a stop in a pasture nestled against a steep forested hillside. Patches of aspen glow golden among the deep green of conifers. Nearby Mean Creek tumbles down from Mount Livingstone to its confluence with Livingstone River.

Smith steps out of the truck and angles his Stetson against the rays of an already intense morning sun. This is a cowboy’s favourite time of year. For the next week, Smith will ride the Livingstone Range with a few wranglers to round up cattle, herd them back to cowboy camp, then truck them to the Plateau Cattle Co. ranch in Nanton.

Last summer, the situation looked even worse. In February 2025, Alberta’s Ministry of Environment and Protected Areas published a foreboding water supply outlook that showed snow in the Oldman, Bow, Athabasca and North Saskatchewan basins as much below average. Late-season snowfall boosted the mountain snowpacks, but it was followed by a wickedly dry spring. By mid-July, numerous Alberta counties and municipal districts, including Pincher Creek, declared agricultural emergencies. Then suddenly, nature’s tap turned on. Drought became deluge. Parched fields turned lush green. Smith estimates the ranch received 180 millimetres of rain in a span of three weeks ­— more than what fell in the last two years combined.

“I don’t know what would have happened if we didn’t get that rain,” Smith says.

It takes a certain kind of resilience to gaze at a blue sky and distant snow-fringed mountains with faith that water will arrive when needed.