OAKLAND, Calif. (October 7, 2020)—Water managers are underprepared for climate change in ways that will leave the state simultaneously at increased risk of water shortages and floods, according to a new analysis released today by the Union of Concerned Scientists (UCS) and accompanying peer-reviewed study in Climatic Change. The volatile swings from very dry to very wet years will become more intense and more frequent by late century as the climate changes. The state experienced exactly this scenario in 2017 and 2018 when bone-dry drought parched the state and left thousands without drinking water then was followed by lethal flooding and mudslides that overwhelmed communities like Santa Barbara and broke Oroville Dam’s spillways.
The UCS study analyzed climate model projections that were developed for the 4th California Climate Assessment and are widely used in state climate planning and guidance documents. The analysis, which looked at where the models’ findings converged, uncovered a troubling picture for California’s water future.
The study found the top ten climate models used by the state government agree there will be nearly complete snowpack loss at lower elevations statewide by the end of the century, if heat-trapping emissions continue to rise as currently expected. The models agree that almost the entire state will struggle with shorter, wetter winters and longer, drier summers and experience many more very wet and very dry years. The expected changes in the length, intensity and volatility of wet seasons, coupled with a dramatically diminished snowpack will, by late century, reduce water supply and require greater and more flexible water storage, including restoration and sustainable use of groundwater aquifers, than currently exists.
The report points out that these predicted climate changes have been overlooked by water managers.
“Water managers have been overly focused for years on the question of how much more or less precipitation we’re going to get because of climate change,” said Geeta Persad, lead author of the report, and assistant professor of climate science at The University of Texas at Austin who authored the report while working as a senior climate scientist at UCS. “This analysis shows that what managers should be asking is not only ‘how much rain or snow will fall,’ but also, ‘how volatile will water flows be from one year to the next?’ and ‘can our water storage systems handle more extremes year after year?’”
According to the study, the frequency of swings between very wet and very dry years will double or triple across most of the state by the end of the century, increasing year-to-year volatility and potentially contributing to fatal mudslides, unexpected wildfire behavior and damage to water infrastructure. That situation could be made worse if the up to 20 percent increase in more extreme precipitation events that create dangerous flood conditions and hard-to-manage flows…