The unprecedented drought that has gripped the Southwest United States has severely depleted the Sierra Nevada snowpack, the major source of water for drinking and farming in California. Researchers and water managers thought this past winter’s monster El Niño would bring enough rainfall to help ease the strain on water resources, but whether El Niño rains were enough to replenish the dwindling snowpack remained to be seen.
Here Margulis et al. calculated daily estimates of this winter’s snowpack volume in the Sierra Nevada using data from Landsat satellites and snow survey data collected by California’s Department of Water Resources. The team also used the satellite images and historical measurements of the snowpack and of past El Niños to estimate the snowpack’s total volume for each year from 1951 to 2015.
The researchers found that this winter’s strong El Niño did not bring enough rain to replenish the snowpack’s depleted stores. In 2015, the water volume of the snowpack was just 2.9 cubic kilometers (0.7 cubic mile), whereas a typical year is about 18.6 cubic kilometers (4.46 cubic miles), according to the study. Accounting for the 4-year snowpack deficit from the 2012–2015 drought, the researchers conclude it will likely take until 2019 for the snowpack to return to predrought levels, even if there are above-average precipitation years.
The team suggest that their method, which provides unprecedented detail and precision, could be useful in characterizing snowpack water in other mountain ranges, including the Andes and the Himalayas. These areas currently have much less on-site monitoring than in the Sierra Nevada.
The larger goal of the research is to build a detailed, continuous picture of the historical snowpack and diagnose the primary factors that cause it to vary. This information can ultimately improve models for predicting how much water will be available from the snowpack in the future, which will inform water management decisions. (Geophysical Research Letters, doi:10.1002/2016GL068520, 2016)
—Lauren Lipuma, Contributing Writer
Correction, 21 July 2016: The spotlight has been updated to correct and clarify how the scientists calculated their estimates.