The severe drought during recent years in California has affected the large masses of snow in the high mountains of the Sierra Nevada, which covers much of the state’s eastern border.

Researchers from the University of Arizona has been able to show that the water density in the snow, that is, how much water the snow actually contain if it would melt, is the smallest in 500 years. It is only one-twentieth of the historical average.

To establish differences in the amount of precipitation through history, the researchers used, among other methods, a form of close analysis of oak trees growing next to the mountains. Studying the width of the rings of this specific species.

They noticed that more that 80 percent of the rainfall occurs during the winter months. This water falls as snow and constitutes a third of the state’s water reserves. Thus, it also affects the amount of water available during the summer months.

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Valerie Trouet et al. Multi-century evaluation of the Sierra Nevada snowpack.
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