California Drought Status Looks Very Different After Extreme Rain and Snow

Months of heavy rain and snow have hugely improved drought conditions in California.

A drought monitor map from October 2022 showed large portions of California to be in an extreme or exceptional drought. The rest of the state was in a severe drought, with very small portions in a moderate drought or abnormally dry.

However a map from February 28, after heavy rain and snow swept across the state, showed vastly different conditions. 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.

California drought map
California drought map
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A side-by-side comparison shows the drought status in California in 2022, compared to after the heavy rain and snow. The U.S. Drought Monitor is jointly produced by the National Drought Mitigation Center at the University of Nebraska-Lincoln, the United States Department of Agriculture, and the National Oceanic and Atmospheric Administration. Map courtesy of NDMC.

California has been in the grips of a drought for two decades. But at the end of February the state was hit by strong snowstorms, even in areas used to bone-dry conditions. An incredibly rare blizzard warning was issued in Los Angeles, as snow fell on low-elevation areas.

A historic amount of rain also fell on the state between December 26 and January 19, and as a result many of the state's reservoirs have seen rising water levels.

The recent rain and snow has been a welcome source of precipitation for the state, providing some storage for its reservoirs.

Hydrologist Roger Bales, a distinguished professor of engineering at the University of California Merced, told Newsweek: "This heavy snowfall will provide seasonal storage, releasing water later in the season, closer to the period it is needed by downstream users for irrigation. It will also release water after the main precipitation period has passed; and for some rivers, the large rim dams may be able to capture a little more water and store it for even later season use."

The precipitation will also help keep vegetation moist in the drier summer months.

"When all snow is melted the upper meter or so of soil dries out within a few weeks. That wetter period for longer may mean more growth for shallow-rooted understory vegetation, which when it dries out or dies provides more fuel for wildfires," Bales said. "On the benefit side, it will mean that potential stress of deeper-rooted vegetation such as the conifer forest is lessened. So the deep snowpack will mitigate the drought effect in the forest by refilling the subsurface-water-storage reservoir in the soil and weathered bedrock til later in the season."

While recent rain and snow has been welcome, the state is not out of the woods yet.

Even though the state's drought status has improved, it will take years of increased rainfall to fully lift its drought status. This is because the drought has been ongoing for so long.

California rain and snow
A compilation image shows heavy rain and snow sweeping California. The Los Angeles River is pictured overflowing in January (top left) while rain pummels the Golden Gate Bridge in San Francisco (bottom). The Yosemite Valley snowpack is pictured above average (top right) David McNew / JOSH EDELSON / Mario Tama

"it is good to remind folks that asking if the drought is over may be the wrong question. We welcome average or above precipitation years, with the caveat that big storms, especially warm atmospheric rivers, increase flooding hazards," Bales said.

"Also, think of California's precipitation as being a series of dry to average years punctuated by a smaller number of wet years. Then subtract a constant value from each annual precipitation amount, to get a much more variable runoff amount. That is, water use by headwater forests is about the same every year, with the remainder being runoff. Even a moderately wet precipitation year may be only an average runoff year. Wet runoff years are much less frequent than dry or average runoff years."

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