Colorado Airborne Snow Measurement Program (CASM)
The Colorado Airborne Snow Measurement Program (CASM) delivers unique, basin-wide snowpack intelligence that protects Colorado’s water supplies, strengthens science, and ensures that every monitoring dollar delivers real value for the future.
Founded in 2020 in the halls of Colorado Water Congress, CASM is a partnership of more than 100 local, state, and federal water partners committed to expanding access to state-of-the-art snowpack monitoring data to improve decision making across all water sectors. Since its launch, CASM has pioneered the use of Airborne Snow Observatories (ASO) lidar snowpack measurement flights in the state as an operational water supply management tool. The data delivered by ASO uses high-resolution basin-wide snowpack mapping–which is ground-truthed and calibrated to local snow measurement stations–to improve forecasting and day-to-day water operations. By pooling resources across agencies, while also building and strengthening unique partnerships amongst diverse water managers, CASM delivers data and insights no single partner could achieve on its own.
In 2025, the Colorado legislature passed HB15-1115: “Water Supply Measurement & Forecasting Program,” which officially establishes a water supply measurement and forecasting program within the Colorado Water Conservation Board (CWCB). This new statewide initiative builds directly on CASM’s successes and reflects an “all of the above” approach: integrating ASO, ground observations, and streamflow forecast models to guide water management and decision-making at the state level.
Program Partners
CASM Program Scope
“ASO provides detailed information into the snowpack like we have never seen before. The information gained from ASO flights allows for a finer level of water management and provides more opportunity to benefit more users and get the maximum benefit out of every drop.”
Nathan Elder, Raw Water Operations Manager, Denver Water
Deliver best-in-class scientific products: CASM delivers Airborne Snow Observatories, Inc. (ASO) outputs that include spatially distributed snowpack measurements, snowpack-constrained streamflow forecasts, albedo, and dust measurements. These products are available through the ASO data portal at data.airbornesnowobservatories.com.
Provide decision-ready insights: Products are designed to feed directly into hydrologic models and forecasting systems, providing actionable guidance during the critical runoff season.
Promote stakeholder education and support: CASM works directly with water managers to build capacity, improve understanding of snowpack and runoff forecasts, and strengthen decision-making under changing conditions.
Support multiple research efforts and improve modeling throughout the West: ASO data delivered through CASM are used by research groups and operational agencies throughout the West to improve snowpack and streamflow forecasts across the state. ASO is recognized by many snow science research groups as “ground truth” by which they can improve their models. Examples include the CU-SWE product developed at the University of Colorado, applications by the Western Water Assessment, the USGS SnowModel efforts, and experimental forecasts by the Colorado Basin River Forecast Center (CBRFC).
Benefits Realized
Operational Case Studies
2023/2024 Dolores Project (DWCD): Early confirmation of extreme conditions enabled managers to adjust allocations and deliveries before runoff. (Link)
2024 Fraser Collection System (Denver Water): Spatial snowpack maps optimized operations across a complex, high-elevation diversion network. (Link)
2024 Northern Water / Granby Reservoir: Improved inflow forecasts supported CBT project operations and long-range planning. (Link)
2019 Dillon Reservoir (Denver Water): ASO provided early warning of potential spills, allowing proactive release management. (Link)
CASM data used to optimize Fraser River Collection System
“ASO data builds upon the great existing snow measurement networks through adding a revolutionary new element: highly accurate estimates of the volume of water in the snowpack reservoir—our largest reservoir here in Colorado. This is information water managers have always needed, and now having it brings a new level of confidence and flexibility in decision making. This data is game-changing for water management.”
Taylor Winchell, Water Supply Planning, Denver Water
Unique Measurement Value
Measuring the snowpack “reservoir”: ASO measurements provide the most accurate estimate of any existing technologies measurements of how much water is in the snowpack reservoir. This information is invaluable to water managers, who every day make complex and difficult decisions that are dependent on knowing the volume of water available in their systems.
Earlier detection of extreme years: ASO measurements identify high or low runoff scenarios before melt begins, supporting early season decision making.
High- and low-elevation volume insights: ASO covers areas outside the tight band of SNOTEL site installations, filling critical data gaps and allowing subbasin-specific water supply estimation and forecasting..
Late-season visibility into melt patterns and remaining snow: Surveys reveal how much snow remains at elevations not covered by existing monitoring networks, helping managers make decisions with limited data.
Seasonal melt timing and distribution: ASO-informed WRF-Hydro streamflow forecasts provide dynamic insights into when and where snowpack is projected to melt, not just how much remains.
An “All-In” Approach to Snowpack Monitoring
ASO is the foundation, but CASM provides a broad approach to snowpack modeling and water supply forecasting. CASM combines multiple monitoring strategies to provide the most complete and robust picture of snowpack conditions:
ASO lidar snowpack measurements show the full distribution of snowpack.
The iSnobal snowpack energy balance model provides spatial and temporal continuity of snow water equivalent between airborne surveys.
WRF-Hydro Streamflow forecasts and continued integration of ASO data into multiple forecasting products translates snow data into insightful and change-resilient streamflow forecasts.
Education and capacity building improve how managers interpret and apply forecasts, supporting smarter decision-making across Colorado’s water sector.
SNOTEL stations and manual measurements anchor monitoring with long-term records and continuous ground truth observations.
Together, these tools create a resilient, decision-ready monitoring system that supports Colorado water managers at every level.
Source: 2025 CASM Activities Memo
Collaborative Funding Approach
Although CASM is largely state funded, with 52% coming from various state funding sources, 48% comes from a broad mix of local, regional and federal stakeholders, who have seen benefits through applying ASO data and the other products from CASM to their operations.
Looking Ahead
CASM is not just about monitoring snow. It is about shaping Colorado’s water future. In partnership with Colorado’s new Water Supply Measurement and Forecasting program, we will continue to:
Support stakeholder education and use cutting-edge technologies.
Explore the use of ASO lidar for other applications, like flood hazard mapping.
Integrate snowpack and streamflow forecasts more directly into operational decision-making.
Guide the siting of new on-ground monitoring stations that complement airborne data.
Promote and apply the latest advances in snow science (software, satellite, drone, and ground-based measurement and forecasting frameworks) to improve accuracy, resilience, and long-term water security for users across Colorado.
Support new approaches for integrating innovative snowpack measurements with streamflow forecasting models
Bottom line: CASM delivers basin-wide snowpack intelligence that protects Colorado’s water supplies, strengthens science, and ensures that every monitoring dollar delivers real value for the future.