California and the Great Basin

In California, the state’s three-year precipitation deficit was just about erased by the atmospheric rivers that caused so much flooding in December and January. By early March, the snowpack across the Sierra Nevada was well above the historical averages — and more than 200% of average in some areas. The Metropolitan Water District of Southern California announced it was ending emergency water restrictions for nearly 7 million people on March 15.

It seems as though most of the surface water drought — drought involving streams and reservoirs — could be eliminated by summer in California and the Great Basin, across Nevada and western Utah.

But that’s only surface water. Drought also affects groundwater, and those effects will take longer to alleviate.

Studies in California have shown that, even after wet years like 2017 and 2019, the groundwater systems did not fully recover from the previous drought, in part because of years of overpumping groundwater for agriculture, and the aquifers were not fully recharging.

In that sense, the drought is not over. But at the broader scale for the region, a lot of the drought impacts that people experience will be lessened or almost gone by this summer. like a very good water year there.

But one single good water year is not going to fill Lake Mead and Lake Powell. Most of the region relies on those two reservoirs, which have declined to worrying levels over the past two decades. NOAA’S seasonal drought outlook released on March 16 noted that both remained low.

Two good water years won’t do it either. Over the next decade, most years will have to be above average to begin to fill those giant reservoirs. Rising temperatures and drying will make that even harder.

So, that system is still going to be dealing with a lot of the same long-term drought impacts that it has been seeing. The reservoirs will likely rise some, but nowhere close to capacity.