Why California Drought Isn't Over Yet

California has been in the grips of a drought for the past ten years. But will that change following the influx of snow and rain that have pummeled the state over the winter. At the end of February the state was hit by severe snowstorms, even in areas used to extremely dry conditions. A historic amount of rain also fell on the state between December 26 and January 19. So is the drought over? There is no doubt that the drought conditions in the state have significantly improved following the weather. In October 2022, large portions of California were in an extreme or exceptional drought, according to the U.S. drought monitor. The rest of the state was in a severe drought, with very small portions in a moderate drought or abnormally dry.

However, since February 28, after heavy rain and snow swept across the state, most of the state is now classed as abnormally dry, while 16.7 percent of the state is not in a drought at all. Some small portions are in a moderate-to-severe drought, while most of the state is abnormally dry. The weather will provide seasonal storage for the state, and release water in the state's reservoirs later in the season. But it will take a lot more than this to fully lift California drought status.

Read more

• California drought status looks very different after extreme rain and snow
• California reservoir water levels before and after winter storm
• Facts about the Mississippi River

Hydrologist Roger Bales, a distinguished professor of engineering at the University of California Merced, told Newsweek: "Drought is a multi-year event. California has some buffer against a single dry year. An example is the very dry 2007, but with 2006 and 2008 being more 'normal' or average years, there were still water deliveries to irrigation and municipal water users. However, during this recent 3-year drought and the 4-year 2012-15 drought, water deliveries were severely curtailed." It would take years of increased rainfall to fully lift California's drought status, as it has been dry for so long. California's reservoirs have been in a dire state due to the drought conditions. The recent rain and snow will help to replenish them, but Bales said there will need to be more storms in 2023 to make an average year. There is also a danger of flooding. When a region has been in a drought for so long, the ground becomes parched, meaning sudden rainfall fails to saturate in the ground. This can cause flash floods. "A deep snowpack may not be the best metric of whether we are seeing a pause in drought conditions. It is also helpful to look at total precipitation. [On March 1] the northern Sierra Nevada precipitation index is at 43.5 inches, compared to a water-year average of 53.2. So we still need more big storms 2023 to be even an average year," Bales said. "The Central and Southern Sierra indices are above the water-year average, which is good for water supply, but potentially bad for flooding if we get a warm atmospheric river coming in that results in faster snowmelt. I also refer to the northern Sierra index, because much of our water supply for southern California and many irrigation users comes from that large, wetter part of the state." California is just one state suffering at the hands of the megadrought gripping the southwestern U.S. The dry conditions gripping this region of the country have been ongoing for over two decades and have been even drier than any other U.S. megadrought within the past 1,200 years. Experts believe human-driven climate change is the main driver of the drought. Do you have a tip on a science story that Newsweek should be covering? Do you have a question about snow fall in California? Let us know via science@newsweek.com.