Laser Missions Show Record Low Snowpack Across Western US

Specialized aircraft have collected data showing record low snowpack across the western United States this spring. The measurements come from missions that use Lidar sensors to map snow depth with high precision. Officials rely on this information to forecast water availability for millions of residents and agricultural operations.

The aircraft operates by emitting about 800,000 laser pulses per second. This produces a three-dimensional map of snow depth accurate to within 3 centimeters. The same technology calculates the volume of water stored in the snowpack. In the western states, mountain snowpack functions as a natural reservoir.

Water managers use the measurements to determine how much meltwater will reach rivers, reservoirs and distribution systems. This year's readings have indicated substantially lower volumes than average. According to the latest US Drought Monitor, more than 60 percent of the lower 48 states are experiencing drought conditions.

This represents the most widespread spring drought since records began in 2000. The western snow drought has compounded the national picture. A record-warm winter and a period of high temperatures in March reduced snow accumulation. The total water stored in western snowpack reached its lowest level on record at the time it should have peaked.

Statewide snowpack in California stood at 18 percent of average on 1 April and has continued to decline.

Measurements taken near Reno, Nevada, show that spring runoff from mountain snowmelt is occurring two months ahead of the historical schedule. Once the snow melts early, the ground begins to dry out sooner than normal. This increases the potential for wildfires during the extended dry period ahead.