Trends in Yellowstone’s Snowpack

Rodman, Ann; Thoma, David; Tercek, Mike

If water is the source of life, then life in Yellowstone is ruled by snow. In the park’s highest elevations, snow often covers the ground until late June. Even in a desert like Gardiner, Montana (MT), melting snow controls the pattern of water availability for the entire year, as seen by the stream flow on the Yellowstone River at Corwin Springs, MT, next to Yellowstone’s northern boundary (figure 1). Each year, flow is characterized by a large spike that begins when snow starts to melt at lower elevations, usually at the end of February or the beginning of March. Peak flow is reached sometime in June when the deep snow fields at medium and high elevations are melting quickly. Minimum flow occurs when all the year’s snow has melted and it is cold enough for precipitation to fall as snow instead of rain, so only water flowing from underground sources can supply the streams. Year after year, the hydrograph is dominated by this pattern of snow melt (figure 1). The proportion of stream flow to the annual snow cycle due to rain storms is merely a blip in comparison. The influence of Yellowstone’s snow reaches beyond the park’s boundaries. The Yellowstone River, the Snake River, and the Green River have headwaters in the mountains in and near Yellowstone National Park. These rivers, in turn, are the largest tributaries of the Missouri, Columbia, and Colorado rivers, respectively (figure 2). Millions of people living on all sides of Yellowstone rely on these rivers for agriculture, drinking water, recreation, and energy production. If Yellowstone receives less snow in the future, the consequences would be widespread. How does the snowpack in recent years compare to the past and are there long-term trends in Yellowstone’s snow data? How much change is attributed to natural climate cycles vs. anthropogenic (human-caused) climate change? This article addresses these questions using data from Yellowstone’s manual snow courses and automated Snow-Telemetry (SNOTEL) weather stations.

Trends in Yellowstone’s Snowpack

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