Precipitation

Low Flows, Hot Trout

Precipitation

MORE RAIN, LESS SNOW: Although our average annual precipitation remained steady or even increased slightly in the Clark Fork basin over the past 50 years, more of that moisture came down as rain instead of snow in Missoula and Kalispell. The trend didn’t hold in Butte, perhaps due to its higher elevation.

WETTER WINTERS AND DRIER SUMMERS: What will we see falling from the clouds in the future? First, it’s important to note that climate models yield less conclusive results for precipitation than for temperature in our region. In its Climate Change 2007 report, the iPCC predicts no significant change for western Montana’s total precipitation over the next century. However, the timing and type of precipitation may shift: the report predicts a 10% increase in precipitation during the winter months, and a 10 to 15% decrease in summer precipitation. As temperatures increase, more of our winter precipitation may be coming as rain, especially at lower elevations.

MORE PRECIPITATION IS FALLING AS RAIN, NOT SNOW, A TREND EXPECTED TO CONTINUE:

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SNOWPACK IN OUR MOUNTAINS ON APRIL 1 DECREASED 30% ON AVERAGE FROM 1950-2000:

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SHRINKING SPRING SNOWPACK: Much of our basin’s economy relies on the seasonal cycle of snow and runoff: agriculture, hydropower, fisheries, recreation and tourism. So, the amount of water stored in our mountain snowpack on April 1st is a vital gauge for predicting not only the summer’s streamflows, it also forecasts the economic health of our communities. And this number has declined over the past half-century in the Clark Fork basin—snowpack in our mountains on April 1st decreased 30% on average from 1950-2000.