August 28, 2010
Graph of the Day: Onset Date of Spring Runoff Pulse in the US West
This graph shows trends in yearly dates of spring snowmelt onset in rivers throughout US West, based on U.S. Geological Survey streamgages. Reddish-brown circles indicate significant trends toward onsets more than 20 days earlier. Lighter circles indicate less advance of the onset. Blue circles indicate later onset. The changes depend on a number of factors in addition to temperature, including altitude and timing of snowfall. Rising temperatures have also led to earlier melting of the snowpack in the western United States. Because snowpack runoff is critical to the water resources in the western United States, changes in the timing and amount of runoff can exacerbate problems with already limited water supplies in the region.
