The hyped and hoped for strong El Nino barely made a dent in California's snowpack deficit, and that is not good news for the state's water supply.
Even if the state receives above-average amounts of rain and snow for the next few years, the snowpack will not replenish to its pre-drought levels until 2019, according to a new study. That could mean that the state has more years of tight water ahead of it — rain and snow from the from the Sierra Nevada mountains makes up about 60 percent of the developed water supply in the state.
"This four-year drought has led to by far the largest deficit on record," said the study's lead author, Steven Margulis, a professor of civil and environmental engineering at the University of California, Los Angeles.
"Going into this past winter, everyone thought El Nino was going to save the day," Margulis said, specifically referring to media coverage that called El Nino a "drought-buster," or oversold its ability to ease the drought. There were really two problems with that hope, he added. First, while strong El Ninos tend to bring a lot of precipitation to coastal areas, their influence over snow in the Sierra Nevadas has been far more mixed. Secondly, the new paper shows that even a strong El Nino would not have been able to fully replenish the snowpack depleted by the drought.
The team used measurements taken by NASA's Landsat satellites taken over the last 31 years. The satellite images provide a more complete picture of the snowpack than the oft-used ground sensors, which are typically stationed at more accessible middle elevations.
They built out a dataset based on the information and ran thousands of possible future scenarios of climate and precipitation levels in the near future. Out of that, they determined that it will likely take about four years for the snowpack level deficit to be paid off.
The results were published Tuesday in the American Geophysical Union's journal Geophysical Research Letters.
Snowpack is a kind of base-layer of snow that accumulates at higher altitudes and sticks around throughout the spring and summer. As it slowly melts, it feeds water to mountain streams and rivers, eventually making its way to reservoirs and irrigation canals.
Much of California undergoes a seasonal drought every summer, and this slowly melting runoff is an especially important source of water in these dry times. Reports out this year already suggest mountain runoff levels are coming up short.