A University of Arizona-led study used the annual growth rings of trees to reconstruct a long-term climate history and examine the duration and frequency of "perfect droughts" in Southern California's main water sources.
Severe droughts happened simultaneously in the regions that supply water to Southern California almost six times per century on average since 1500, according to new University of Arizona-led research.
The study is the first to document the duration and frequency of simultaneous droughts in Southern California’s main water sources – the Sacramento River basin, the Upper Colorado River Basin and local Southern California basins.
The report highlights what a previous researcher dubbed “perfect droughts" – when the precipitation or streamflow in all three water sources falls below the median for two or more years. The most recent perfect drought lasted from 2012 to 2015.
Concurrent droughts lasting multiple years in all three sources of water for Southern California pose “the most serious challenge to water management,” the authors write in the Journal of American Water Resources Association.
The researchers used the annual growth rings of trees to reconstruct the climate history of the three water sources back to the year 1126. For the period 1906 to 2017, the amount of annual precipitation and streamflow was recorded by instruments.
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