Arizona State University and Salt River Project are working with Airborne Snow Observatories Inc. on an innovative project to measure snowpack in the Salt River watershed — providing crucial data to improve water management and water supply forecasting.
For the first time, a collaborative research team is using an airplane equipped with state-of-the-art scanning lidar and imaging spectrometers, along with innovative computational modeling from ASU, to measure snowpack and determine how much water it contains. The NASA Jet Propulsion Laboratory developed the airborne technology.
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The data collected during the flights will be analyzed and used to test hydrologic forecasting models developed by ASU Professor Enrique Vivoni with the School of Sustainable Engineering and the Built Environment. Vivoni is the primary investigator for the joint project.
“Mapping snow cover with these airborne technologies is a first of its kind for the state of Arizona,” said Vivoni, also with the Arizona Water Innovation Initiative in the Julie Ann Wrigley Global Futures Laboratory. “We are excited about using snow maps in forested regions of the Salt River to improve runoff forecasts and train algorithms that apply artificial intelligence.”
The study’s findings will help SRP more accurately forecast runoff into the seven reservoirs that supply water to more than 2.5 million Valley residents.
The ASO Inc. flights will focus on the basin areas upstream of the Roosevelt Dam on the Salt River in the Upper Black River Basin area near New Mexico. A pilot and scientist on board will fly across the entirety of the basin several times during four- to five-hour flights, gathering data on snow conditions. Depending on weather, three flights are scheduled through March with the first leaving Safford, Arizona, on Jan. 21.
SRP uses a variety of tools to measure snow water equivalent across the watershed to manage the 260 billion gallons of water delivered annually to the Valley. The SRP watershed has historically been challenging to measure precipitation and runoff due to rapidly changing snowpack conditions in the forested regions.
“This project is so critical because it will enable SRP to strengthen our measurement tools and provide more accurate data as we manage the reservoirs,” said Bo Svoma, SRP climate scientist and senior meteorologist.
An SRP snow survey occurring on the same days will provide additional information to complement the data gathered from the ASO flights. SRP crews will be on the ground measuring the snow water equivalent and depth, and flying over snow markers to estimate depth at many locations.
The project is made possible by a United States Bureau of Reclamation grant to ASU’s Center for Hydrologic Innovation and SRP’s Innovation and Development Program, which funds collaborative research projects with Arizona universities on a variety of topics important to SRP.
The Arizona Water Innovation Initiative, a statewide project that rapidly accelerates and deploys new approaches and technologies for water, is also supporting the project. ASU professors, researchers and students are working closely with SRP scientists and engineers on projects aimed at improving SRP’s water and power operations.
ASO uses an airborne remote sensing platform to measure the most critical snow properties: snow depth, how much water is stored in the snowpack and the reflectivity of the snow. Each of these properties varies across landscapes and with changing environmental conditions, such as precipitation, wind and temperature. The airborne measurements are used in snowpack hydrology models to track the snowpack evolution over the season and to forecast snowmelt runoff.
Like radar but using light, lidar sends beams from a plane toward the ground. By measuring the time it takes for the light to be reflected back to the instrument in the airplane, scientists can calculate the depth of snow every 10 feet across the landscape. The flights also use an imaging spectrometer to measure the reflectivity of snow, which is a critical driver in how fast the snow will melt over time.
The ASO team will rapidly process that data to generate spatially complete maps of the area’s snow.
This technology does not replace SRP’s measurement tools or SNOTEL, an automated network of remote sensors maintained by the USDA’s Natural Resources Conservation Service. These tools remain foundational for snow monitoring. Instead, it will help fill in gaps and strengthen the ability to forecast snowmelt entering the reservoirs, enabling SRP to effectively manage the watershed.
“The ASO data, along with satellite imagery from Planet Labs, is helping us to monitor the ephemeral snowpacks in the Salt River, which distinguish us from other parts of the Western United States,” Vivoni said. “This information is then used to feed hydrologic forecasts that provide state-of-the-art runoff predictions that help manage water supply in Arizona.”
