Colorado’s mountain snowpack is beginning to melt faster, potentially bringing more high tides after recent heavy rains turned some of the state’s typically weak creeks into torrential downpours.
Large water rose to 80 times higher than the norm this week during downpours in Colorado Front Range cities, forcing police in Denver to warn creekside campers who have no housing to clean up, and are scrambling 30 firefighters in Colorado Springs who recovered the body of a wiped person.
More rain fell on Friday — and National Weather Service meteorologists are predicting thunderstorms almost every day next week — saturating soils enough for water to gain strength more easily.
“The risk of flooding is out there,” says hydrologist Brandon Forbes of the U.S. Geological Survey, which manages the federal government’s 360-meter network of rivers and creeks across the state that provide cubic feet per second (cfs) of water flow. dimensions every 15 minutes.
“Certainly on the western slope, all of our meter readings will increase as the snow melts in the coming weeks,” Forbes said. “We are preparing for high flows on Colorado’s Western Slope in the next two weeks to a month. For flood risk, the slower it melts, the better. It all depends on the weather.”
Overall surging currents from a combination of snowmelt and heavy rainfall hit Colorado this week amid growing interest in how global warming is changing water dynamics — driven by increasing human competition for water in the generally arid Southwest.
Atmospheric scientists have long anticipated a shift from snow as the primary form of precipitation in Colorado and the high Rocky Mountains to more moisture falling as rain. Warmer air — temperatures in parts of western Colorado have risen faster than the global average — can hold more water and also release more water as rain, sometimes in bursts during extreme storms. A federally sponsored study project in the mountains above Crested Butte, it measures how much moisture from mountain snowpack is lost to warming air—the “sublimation” of snowpack converted directly to water vapor, reducing the water from melting snow that reaches streams.
“A warming climate is expected to result in reduced mountain snow runoff, due in part to a greater demand for evaporation — the atmosphere’s ‘thirst’ for water — which increases as temperatures rise,” said state climatologist Russ Schumacher, referring to a 2021 University of Colorado study. .'”
Mountain snowpack in watersheds feeding the Dolores, Animas, Gunnison, Yampa, Colorado and other rivers in the westernmost parts of Colorado was exceptionally high this year, promising the greatest runoff. Mountains east of the Continental Divide received relatively less snow. The South Platte watershed had almost average snow, and snow in the Arkansas River Basin lagged, peaking at about 74% of the 1999-2020 standard.
Meanwhile, heavy rains — falling in scattered bursts around Colorado since May 9 — have led to unusually high flows in creeks and rivers. On Thursday, the Arkansas River burst its banks in southeastern Colorado near La Junta, flooding US 50. Coal Creek west of metro Denver burst its banks last week, forcing Colorado 52 to close.
In Denver, intense rain on May 11 resulted in muddy brown currents flowing through the city into Cherry Creek at 1,300 cfs, the highest since 1980, federal data shows. (The U.S. Army Corps of Engineers operators of the dam in the Cherry Creek Reservoir last week began regularly scheduled seasonal releases of reservoir water from the dam into the creek, which contributed to the infusion of rain. The floods are so much higher ,” Forbes noted.)
Along Monument Creek, as it flows through central Colorado Springs, a USGS team led by Forbes last week measured the flow at 4,000 cfs, 80 times higher than the 50 cfs standard for this time of year. South of Colorado Springs, where Monument Creek joins Fountain Creek, data shows a flow of 5,000 cfs, above the standard at that location of 80 cfs.
Water levels in the South Platte River northeast of Denver near Fort Morgan, averaging around 300 cfs over 36 years, reached a high flow of 5,930 cfs on May 14, data shows.
And on the Arkansas River a mile east of Pueblo, the flow rate exceeded the norm from 900 cfs quintupling to 4,780 cfs on May 12.
On Friday morning, a light rain fell amid fog and smoke spreading from Canadian wildfires, USGS measuring station data showed the following relatively high flows around Colorado from both rain and melting mountain snow runoff:
- The Cache La Poudre River at Fort Collins: 1,330 cfs, above the standard of 575 cfs,
- South Platte River in Commerce City: 1,160 cfs, above the norm of 649 cfs,
- Sand Creek where it meets the South Platte: 178 cfs, above the norm of 121 cfs,
- Bear Creek southwest of Denver near Morrison: 289 cfs, above standard of 121 cfs,
- Big Thompson River below Moraine Park near Estes Park: 288 cfs, above standard of 153 cfs,
- The Colorado River at the Utah border: 35,400 cfs, above the standard of 14,499 cfs,
- Colorado River at Windy Gap (near Granby): 1,800 cfs, above standard of 632 cfs,
- Colorado River at Kremmling: 2,600 cfs, above standard of 1,930 cfs,
- Gunnison River (near Gunnison): 4,060 cfs, above the norm of 1,690 cfs, and
- Dolores River at Bedrock: 4,120 cfs, above the norm of 820 cfs.
Around Colorado, the rains since May 9 have heavily saturated the soil. This means that the more rain there is, the greater the risk of flooding.
“The watersheds are now prepared,” Forbes said. “Because the soils are so wet, they don’t have much capacity to hold rain. Water drains faster, so the risk of flooding is greater.”
When the mountain snowpack melts, it gradually trickles into streams and rivers in western Colorado, often described by urban and agricultural water supply managers as a natural, timeless reservoir. On the other hand, when precipitation takes the form of rain, creeks can burst their banks in less than an hour because there is a sudden abundance of water.
But high tides won’t last, Forbes said. “It’s going down really fast.”
