Western US Snow Drought Winter 2018
Snow melt provides a sustained source of water for over one billion people globally and is a critically important resource in the western US and in California where the Sierra Nevada snowpack supplies one-third of the state's water supply.[1] In recent years, snow water equivalent (SWE)—the amount of water stored in the snowpack—in the western US has significantly diminished.[2]
Long-term climate warming is strongly correlated with declining snow water equivalent. And shifts in stream flow throughout the American West have been driven by decreased spring accumulation and/or increased spring melt.[3] The fingerprint of warming temperatures has been found in these trends at both broad scale[4][5][6][7] and in California in particular.[8][4][9][10]
SWE is measured on approximately the first of each month in the mountains of the western US during the winter season and reaches its basin-wide maximum on approximately April. These measurements indicate the condition of water resources. By February 2018, water resources in several states were a fraction of the historical average.
Many western states including California, Utah, Oregon, Washington, and Colorado are in the midst of a warm, dry winter.[11] In January, almost all of the open resorts in New Mexico, Arizona, Colorado, Utah, Nevada, and California were relying on man-made snow to operate.[11] These states have also experienced worsening drought in recent months.[12]