This winter’s abnormally hot, dry conditions dealt a major blow to snow stored in Arizona’s mountain ranges. A new survey of snowpack in the Salt River Watershed tracked plummeting snow totals using high-tech sensors attached to airplanes, helping water managers make plans for a major Phoenix-area water supply.
Between late February and the middle of March, snow totals dropped by more than 90% in the Upper Black River basin. The mountainous region of eastern Arizona contributes snowmelt to the Salt River system, which fills reservoirs like Roosevelt Lake. That is part of the Salt River Project, which supplies water to more than 2.5 million people around the Valley.
Enrique Vivoni, an Arizona State University professor who directs the school’s Center for Hydrologic Innovations, worked on the study. He said the planes add a level of precision to snow data that can help water managers fine-tune their strategy for releasing water from reservoirs.
“What's critical about this is the timing,” he said. “When will that water that's previously been in the snow and now is in the soil, when it will arrive to the rivers and eventually to the reservoirs, and that timing information is really important for water management.”
The Salt River Project and Airborne Snow Observatories, Inc. also worked on the project. Water planners already measure snow using a network of fixed sensors on the ground, but Vivoni said the new aerial surveys will help produce more accurate forecasts in the future.
“It does start to beg the question,” he said, “How do we prepare for a future where runoff might be coming earlier, where we might need to be making decisions about reservoir management earlier than we did before, where we might need to depend more on the rainfall events that arrive in the summertime.”
Snowmelt is a critical part of the water supply in Arizona, and climate change is making it scarce. High temperatures are causing it to melt earlier around the Western U.S.
That pattern is especially acute in the Colorado River basin, causing shortages that may force cutbacks to Arizona’s share of the river. That may make the Salt River system even more important to the cities that depend on its water.
EDITOR'S NOTE: This story has been updated to correct Airborne Snow Observatories, Inc.'s name.
