Rain over California’s Owen’s Valley in early May 2016. The 2015–2016 El Niño, which officially ended in late May, was one of the strongest El Niños on record.
Rain over California’s Owen’s Valley in early May 2016. The 2015–2016 El Niño, which officially ended in late May, was one of the strongest El Niños on record. Although predicted to bring heavy rainfall to California, new research shows El Niño’s rains were not enough to ease California’s ongoing drought. Credit: Dustin Blakey, CC BY-NC 2.0
Source: Geophysical Research Letters

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.

This animation shows the change in snow water equivalent in the Sierra Nevada mountains from 1985 to 2015. New research shows even with this winter’s strong El Niño, the Sierra Nevada snowpack will likely take until 2019 to return to pre-drought levels. Credit: Steve Margulis/UCLA

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.


Lipuma, L. (2016), Monster El Niño not enough to quench California drought, Eos, 97, https://doi.org/10.1029/2016EO055707. Published on 15 July 2016.

Text © 2016. The authors. CC BY-NC-ND 3.0
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