Gallatin River Basin

Snow Water Equivalent (SWE)

The amount of water contained in the snowpack. It is measured using the "Snow Pillow" at mountain SNOTEL sites, and measured by a Federal Snow Sampler at manual snowcourse measurements. It is a useful metric for gauging potential runoff from the melting of the snowpack in the Spring.

Basin-Wide Snow Water Equivalent

Snow Water Equivalent - Monthly Change (Delta)

Sub-Basin Snow Water Equivalent


Measured at mountain SNOTEL sites using a storage gage and at valley COOP weather stations using a combination of tipping buckets and storage gauges. Precipitation data is measured hourly at many sites, but is only collected monthly for COOP weather stations by the NRCS' Air and Water Database (AWDB). As such, data for valley precipitation stations is only available for the monthly time period. 

Water Year To Date Precipitation (beginning October 1st)

Monthly Precipitation - Mountain SNOTEL Sites (1st of Month for Previous Month)

Monthly Precipitation - Valley COOP Sites

Reservoir Storage

Paragraph on Reservoir Storage

Reservoir Storage (1st of Month)

Streamfow Forecasts

Paragraph on Streamflow Forecasts

Streamflow Forecasts - 50% Exceedance Probability


The Unofficial Montana Snow Survey