Molotch

The data is in: Colorado’s snowpack is lagging behind the 21st century average in 2025

Gabe Allen — Thu, 10 Apr 2025 16:30:00 +0000

The data is in: Colorado’s snowpack is lagging behind the 21st century average in 2025 Gabe Allen Thu, 04/10/2025 - 10:30

Gabe Allen

A new modeling tool from INSTAAR provides weekly snow-water equivalent estimates for the entire Western US.

Last week, INSTAAR’s Mountain Hydrology Group released its fifth near-real-time report on snow-water equivalent (SWE) in the Western US in 2025. In essence, the report provides a snapshot of how much water is stored in snow on the landscape—water that will feed our rivers and streams in the months to come.

The end-of-March report is of particular interest for water managers in the West, because it arrives around the time that snow in the region reaches its peak. Last week’s report will help managers adjust plans for the spring, summer and fall.

“It helps inform how much water storage they might have and when that might come down into their reservoirs,” INSTAAR PhD student and report co-author Emma Tyrrell said.

Other tools for visualizing the snowpack exist, such as the Natural Resources Conservation Service Snow and Water Interactive Map, which plots various SWE-measuring stations. But, the Mountain Hydrology Group’s reports take a uniquely comprehensive approach. The team combines multiple data sources and modeling tools to estimate the amount of water stored in snow across the entire landscape.

The skinny

A map showing the percent of the long-term (2001 to 2021) average snow-water equivalent in major regions of the Western United States as of March 31, 2025.

Here in the Front Range, the report shows SWE totals lagging behind the 2001 to 2021 average. However, the overall trend doesn’t hold at all elevations. While the plains and foothills have less snow than average, many mountainous areas, like the headwaters of the Colorado River, sport average or higher-than-average snowpacks.

“Where you might go skiing, we’re seeing around 100% of normal,” Tyrrell said.

If you zoom out to the entire Western US, the report shows some anecdotal regional trends. The Desert Southwest has had a dry winter, with many regions dipping below 50% of average SWE and some in the single digits. On the other hand, a pocket of mountainous regions in the Northwest, stretching from Western Wyoming to Oregon, is experiencing an unusually robust spring snowpack.

“We’re seeing a somewhat typical north to south gradient during a La Niña cycle,” senior professional research associate Leanne Lestak told INSTAAR.

An experiment, a product

The Mountain Hydrology Group, led by INSTAAR faculty fellow Noah Molotch, has been producing SWE reports for the Sierra Nevada Mountain region in California since 2012. There, water managers and river forecasters have come to rely on the reports.

“We work really closely with the California Department of Water Resources." Lestak said. “The hydrologic engineers use our data in their forecasts, and they really rely on what our reports have to say. It’s such an honor to work with these folks.”

The west-wide report is a newer endeavor—the group put out the first of its biweekly reports this February. Like the Sierra Nevada reports, the west-wide reports draw on a mix of satellite imagery, remote snow sensors and statistical modeling to arrive at its estimates. When they can, the team also calibrates their results by comparing them to “Airborne Snow Observatories,”—intermittent snow surveys conducted via manned aircraft in Colorado and elsewhere.

“We consider them a ground truth,” Tyrrell said. “It’s a patchwork of data that we can use to bias correct.”

While the methodology that the CU team uses for the Sierra Nevada reports has been refined by years of tweaking, the west-wide methodology is still new—it’s an experimental product. It will take a few years for the team to refine the model and build trust with stakeholders.

Locally, the project has already garnered some interest.

“Denver Water and other local cities are interested,” Lestak said. “There aren’t a lot of products here on the Front Range.”

We may have reached peak SWE for 2025 here in the west, but the Mountain Hydrology Group will keep issuing reports until mid summer. All the while, they will work to refine their tools.

If you have questions about this story, or would like to reach out to INSTAAR for further comment, you can contact INSTAAR Communications Specialist Gabe Allen at gabriel.allen@colorado.edu.

A new modeling tool from INSTAAR provides weekly snow-water equivalent estimates for the entire Western US. It has already caught the attention of local and regional water managers.

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Framing the climate conversation through art, science and community collaborations (CU Boulder Community Outreach & Engagement)

Anonymous — Fri, 31 May 2024 21:55:16 +0000

Framing the climate conversation through art, science and community collaborations (CU Boulder Community Outreach & Engagement) Anonymous (not verified) Fri, 05/31/2024 - 15:55

Jane Appel , CU Boulder

Coloradans are experiencing climate change. Residents face challenges like fires, drought and poor water and air quality. The Colorado Arts Science Environment Program’s (CASE) is addressing critical environmental and social issues across Colorado through a collaborative exhibition that brings together CU Boulder scientists and artists from various parts of the state.

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A new look at western water

Anonymous — Thu, 04 Apr 2024 23:38:43 +0000

A new look at western water Anonymous (not verified) Thu, 04/04/2024 - 17:38

Shelly Sommer

The Mountain Hydrology Group will be developing a new snowpack data set to inform water supply management in the western United States, thanks to grant funding from the U.S. Bureau of Reclamation.

Maps show various aspects of snow-water equivalent for California's Sierra Nevada. The maps are part of the April 1, 2024 report from the Mountain Hydrology Group.

Researchers in the Mountain Hydrology Group currently produce near-real-time estimates of snow water equivalent, or the amount of water contained in fallen snow, for mountainous areas in California, Colorado, New Mexico, Utah, and Wyoming. Reports and data are released to water managers and forecasters and are also available to the public.

With the new grant of $1 million over the next three years, the group will be able to expand its estimates to all 17 western states, notably adding mountainous areas in Idaho, Montana, Oregon, and ��Ĺ��ý and large mountain ranges such as the Cascades and northern Rocky Mountains.

The grant will support Noah Molotch (lead PI), Leanne Lestak, Emma Tyrrell, and Karl Rittger in analyzing snow data and producing biweekly snow water supply reports to support decision making by federal, state, and local water management entities responsible for managing water supplies in the western United States.

The Bureau of Reclamation awarded funds to 15 different projects as part of its Snow Water Supply Forecasting Program to improve water supply forecasting.

Photo at top of the page: Noah Molotch shows information about the snow-water equivalent for California during a television interview at NASA Jet Propulsion Laboratory. Photo copyright by and courtesy of Pier Gagné, Radio-Canada.

The Mountain Hydrology Group will be developing a new snowpack data set to inform water supply management in the western United States, thanks to grant funding from the U.S. Bureau of Reclamation.

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LogOn: Satellites, lasers help estimate snowpack in drought-stricken regions (VOA)

Anonymous — Wed, 27 Dec 2023 21:53:47 +0000

LogOn: Satellites, lasers help estimate snowpack in drought-stricken regions (VOA) Anonymous (not verified) Wed, 12/27/2023 - 14:53

Matt Dibble

Video interview with Noah Molotch about how remote sensing technology is helping forecast water availability in the Rocky Mountains. Watch this two-minute, well-edited interview, interspersed with clips of fieldwork and explanatory illustrations.

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Californie, quand l'impensable se produit (Radio-Canada)

Anonymous — Sat, 09 Dec 2023 22:10:25 +0000

Californie, quand l'impensable se produit (Radio-Canada) Anonymous (not verified) Sat, 12/09/2023 - 15:10

France Beaudoin

If there's a place that embodies climate extremes and their impacts on agriculture, it may be California. After years of drought, last spring devastating floods hit the state of the West Coast. Noah Molotch weighs in on the hydrology. (French language broadcast.)

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Colorado artist, CU Boulder scientist band together to spotlight Dillon Reservoir and the state’s water issues (Summit Daily)

Anonymous — Mon, 26 Jun 2023 17:05:52 +0000

Colorado artist, CU Boulder scientist band together to spotlight Dillon Reservoir and the state’s water issues (Summit Daily) Anonymous (not verified) Mon, 06/26/2023 - 11:05

Robert Tann

Their collaborative art piece, part of a CU Boulder-sponsored exhibit, is one of several hanging in the Colorado State Capitol building.

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Scientists take flight to map California’s vast snowpack and measure flooding threats (L.A. Times)

Anonymous — Fri, 26 May 2023 20:15:00 +0000

Scientists take flight to map California’s vast snowpack and measure flooding threats (L.A. Times) Anonymous (not verified) Fri, 05/26/2023 - 14:15

Ian James , Los Angeles Times

Noah Molotch is quoted in this Los Angeles Times article about mapping the recent historic snowpack in California using laser pulses and spectrometers from the air. The flights are collecting data to estimate when and how fast the snow will melt, helping officials prepare for the runoff, manage water releases from dams, and asses areas at risk of flooding.

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Earlier snowpack melt in the West could bring summer water scarcity (CU Boulder Today)

Anonymous — Thu, 25 May 2023 22:54:48 +0000

Earlier snowpack melt in the West could bring summer water scarcity (CU Boulder Today) Anonymous (not verified) Thu, 05/25/2023 - 16:54

Kelsey Simpkins , CU Boulder

Snow is melting earlier, and more rain is falling instead of snow in the mountain ranges of the Western U.S. and Canada, leading to a leaner snowpack that could impact agriculture, wildfire risk and municipal water supplies come summer, according to a new CU Boulder analysis. Kate Hale and Noah Molotch are authors on the study.

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Art and climate science converge in new exhibit at the Colorado Capitol (KUNC)

Anonymous — Wed, 24 May 2023 21:46:29 +0000

Art and climate science converge in new exhibit at the Colorado Capitol (KUNC) Anonymous (not verified) Wed, 05/24/2023 - 15:46

Emma VandenEinde

An exhibit that just opened in the Colorado capitol building's rotunda features artwork made in the process of partnerships between artists from around Colorado, their communities, and CU Boulder scientists. Called “Coloradans and our Shared Environment in Times of Challenge and Change,” the art grapples with the climate and environmental challenges that are part of Coloradoans' lives: drought, decreasing groundwater, acid mine drainage, wildfire, pine beetle tree mortality, and more.

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Coloradoans and our shared environment in times of challenge and change (CU OOE)

Anonymous — Thu, 18 May 2023 18:02:12 +0000

Coloradoans and our shared environment in times of challenge and change (CU OOE) Anonymous (not verified) Thu, 05/18/2023 - 12:02

CU Office for Outreach and Engagement

A collaborative exhibition tells the story of how Coloradans are experiencing interrelated challenges of fire, drought, and water and air quality in their communities. Artists (the CASE Fellows) partnered with scientists and communities to make visible the connections between Coloradans and their environment. Several INSTAARs acted as scientist partners. This website showcases the artwork, as well as quotes from the partners, explorations of the issues, and what you can do to act.

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