A majority of the water in the western U.S. comes from snowmelt.
Source: USGS Water Resources Mission Area
Snow-capped mountains, where snow accumulates all winter and often well into spring, function as frozen water towers by storing water as snow into late spring and summer1.
When spring weather arrives, and the snow melts, the high elevation areas produce a large pulse of streamflow that redistributes water downstream through the landscape. These seasonal dynamics are critical components of the surface water cycle in the Western U.S., for both humans and ecosystems.
Changes in the timing, magnitude and duration of snowmelt may substantially alter downstream water availability. Approximately 2 billion people are expected to experience diminished water supplies because of seasonal snowpack decline this century. Over the last half century, particularly in some regions of the Western U.S., annual snowpack levels have declined and contributed to reduced of streamflow, a trend supported by both models and on-the-ground observations.
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