# What is SNOTEL? > SNOTEL is the USDA Natural Resources Conservation Service network of automated snow-measuring stations across the western mountains, roughly 900 of them. Each station weighs the snow sitting on a pillow to measure its water content, and those readings are the backbone of western water-supply forecasting. _Updated Jul 21, 2026._ SNOTEL, short for Snow Telemetry, is the automated network the USDA Natural Resources Conservation Service runs to measure mountain snow across the West. Roughly 900 stations sit in the high country of the western states, reporting on their own every day. When you read a snowpack number for a state or a basin, it almost always traces back to SNOTEL. ## How a station works The heart of a SNOTEL station is a snow pillow, a large fluid-filled bladder on the ground. As snow piles up on top of it, the weight of that snow presses down and raises the pressure inside the pillow. The station reads that pressure and converts it directly into snow water equivalent, the depth of water held in the snow above it. A station also measures accumulated precipitation and air temperature, and it transmits its readings automatically, which is what lets the network report daily through the winter without anyone climbing the mountain. ## From one ridge to a basin number A single station on a single ridge is a data point, not an answer. Snow varies enormously with elevation and aspect, so any one site can run high or low against its neighbors. The useful number comes from combining many stations. This site uses the basin-index method: it sums the water content across every reporting station in a state or basin, sums those same stations' long-term medians, and divides the two. That rolls hundreds of individual pillows into one honest read on how a whole basin's snowpack compares to normal. ## The normal it compares against SNOTEL readings become meaningful when set against a baseline, and the standard baseline is the 1991-2020 median for each date. A station with a long enough record carries that median alongside its current reading, so the network can report not just how much snow is out there but how much is normally out there on this day. Stations too new to have a 30-year record still report their current water content, but they are left out of the percent-of-median math so they never distort the comparison. ## Worked example [Chart: Upper Colorado River Basin snowpack (snow water equivalent)](https://the-waterline.com/snowpack/upper-colorado-river-basin) ([data](https://the-waterline.com/snowpack/upper-colorado-river-basin.md) — chart image: https://the-waterline.com/charts/snowpack/upper-colorado-river-basin/chart.png) The chart above is the Upper Colorado River Basin snowpack, built from the SNOTEL stations inside the basin using the method described here. The current-year line is the summed water content across those stations, and the median line is their combined 1991-2020 normal for each date. That single basin index, drawn from many ridge-top pillows, is what feeds the runoff outlooks for the reservoirs downstream. ## Related data + guides - [Snowpack tracker](https://the-waterline.com/snowpack) - [Upper Colorado River Basin snowpack](https://the-waterline.com/snowpack/upper-colorado-river-basin) - [What is snow water equivalent?](https://the-waterline.com/guides/what-is-snow-water-equivalent) - [How to read percent-of-median snowpack](https://the-waterline.com/guides/how-to-read-percent-of-median-snowpack) --- Canonical URL: https://the-waterline.com/guides/what-is-snotel