Due to its importance as a water source, officials began monitoring the snowpack in the 1930s, and have established 108 measuring stations throughout the Sierra Nevada.
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Belmecheri pointed out that it’s not just the low rainfall that has scientists concerned but the combination of low precipitation and high temperatures that reduces stores of water in the state’s reserves.
A single tree ring could be influenced by several years of environmental stress caused by any number of factors, he said.
When California Governor Jerry Brown stood in a snowless Sierra Nevada meadow on April 1 and ordered unprecedented drought restrictions, it was the first time in 75 years that the area had lacked any sign of spring snow.
This is probably the biggest water supply concern our state is facing. “Anthropogenic warming is making the drought more severe”.
Satellite images comparing Sierra Nevada snow cover in 2010 and 2015.
“Snow is a natural storage system”, she said.
“You can think about it like a water bank that can be used later in the spring and the summer when it melts”, she said.
The study researchers suggested that the new design could also include maybe changing where the water is captured. California suffered devastating wildfires this week that were fuelled by the region’s worst drought on record. In a winter with less snow or with winter precipitation coming as rain rather than snow, there is less water to use during California’s dry summers. [Soumaya Belmecheri et al, Multi-century evaluation of Sierra Nevada snowpack]. They combined the rainfall chronology with tree ring data that showed temperature fluctuations to determine the severity of the current four-year-long drought.
Now bioscientist Valerie Trouet and colleagues from the Laboratory of Tree Ring Research at the University of Arizona, Tucson, have looked carefully at proxy evidence preserved in the annual growth rings of more than 1,500 blue oaks (Quercus douglasii) at 33 locations in California’s Central Valley.
From that and other data, they have reconstructed a timeline and a record of the annual winter precipitation in California from 1405 to 2005.
Now researchers say this year’s record-low snowpack may be far more historic – and ominous – than previously realised.
The different measurements all lined up – when winter precipitation was lower and temperature was higher, snowpack was lower.
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Belmecheri said the snowpack study confirms that conclusion about the impact of climate change. The National Science Foundation, the U.S. Geological Survey and the Swiss National Science Foundation funded the research.
