The Snowpack: Forecasting Water Supplies

The water outlook this winter isn’t very rosy so far, although with a few more months of snow accumulation season yet to come, we can keep our fingers crossed and hope for more storms later in the season.

As of January 20, 2016, measuring stations in the mountains east of the Salt Lake Valley showed 83% to 99% of the official average Snow Water Equivalent, or SWE. While that may not sound too bad, it comes on the heels of several years of drought. Reservoir levels for the state as a whole are less than 70%, which is below average for this time of year. Since 70-90% or more of the water we use in Utah comes from snowpack, a good snow season is crucial for getting the water we need throughout the year.

Measuring the Snowpack

Although we can’t make it snow and can’t predict exactly how much snow will fall, we can measure what’s up there and compare it to past years in an effort to predict what the coming year’s water supply will be.

In the 19th century, measuring methods were quite primitive. Draper Irrigation used to “measure” the snow depth by using binoculars to sight a certain tree in Big Willow canyon, then compare the depth of the snow around that tree to past years.

In 1935, the federal government began measuring snowpack through the Natural Resources Conservation Service, or NRCS, which still measures snow today. Employees hiked into designated “snow courses,” usually on north-facing slopes protected from the wind, and pounded aluminum tubes into the snow to measure its depth and density to come up with the SWE. In later years, the workers flew into the snow courses on helicopters.

In the 1970s, the NRCS began using Snow Telemetry, or SNOTEL, technology in 11 western states to measure snow depth. Each SNOTEL station (there are 128 in Utah) includes equipment to measure snow density, precipitation in all seasons, air temperature, and soil moisture and temperature at depths varying from two inches to 40 inches. The solar-powered stations then beam the data to the NRCS. Although each station costs around $15,000 to install, they are a money-saving measure because the NRCS no longer needs to use expensive helicopters to ferry workers to the stations. Each station is inspected and maintained roughly once a year.