Following three consecutive years of drought in California, the Sierra Nevada snowpack is one of the most bountiful in more than 40 years. While the record snowpack and snow water equivalent is great news for water supply, there are concerns the record snowpack could create flooding issues.
California has one of the most complex water systems in the world. And so, the factors giving rise to our region’s floods are more complicated than the simple cascading of rain and snowmelt downhill during a rainier-than-average wet season.
We are well into one of the wettest winters on record in the San Joaquin Valley. Historic precipitation levels have buried the high Sierra Nevada under more than 50 total feet of snow. And parts of the Valley, stricken for years by severe drought, are underwater.
A cold low pressure system spinning off the coast of California sent bands of rain and snow across the state Wednesday, making travel difficult and adding to an epic mountain snowpack.
Forecasters said the storm was not as strong as the systems that pounded the state all winter, but that chains were required for vehicles on highways through the Sierra Nevada. A section of U.S. 395 on the eastern side of the range was closed due to snowfall.
In California, the snowpack is at some of the highest levels in recorded history.
The state’s snowpack accumulates in the Sierra Nevada—a mountain range that stretches for 400 miles from Northern California southward to the Great Basin. The snowpack, which melts into the state’s reservoirs, provides about a third of California’s total water supply.
Since the beginning of 2023, California has seen a record-setting amount of snow across the state, especially in the Sierra Nevada, setting up the state to close in on the records for the highest snow water equivalent, which was reached just over a decade ago.
Snow water equivalent is the amount of water that would result from melting the snowpack, according to the UC Berkeley Central Sierra Snow Lab.
No one really knows how much snow fell on the infamous Donner Party when the pioneers were trapped atop the Sierra Nevada for months and dozens died near Lake Tahoe in the winter of 1846-47.
But this season has now etched its way into the history books as the second snowiest in the 77 years of record-keeping at the Central Sierra Snow Lab — more than 56.4 feet (677 inches, 17.2 meters) with no end in sight.
NOAA’s U.S. Spring Outlook indicates the abnormally wet winter will further improve drought across much of the western U.S. as the snowpack melts in the coming months. Winter precipitation, combined with recent storms, wiped out exceptional and extreme drought in California for the first time since 2020, and is expected to further improve drought conditions this spring.
Significant flooding in the western U.S., especially in California, followed another series of strong Pacific storms that battered the region in March, and piled on to an already historic snowpack.
A series of atmospheric river events with heavy rain and snow have caused California water regulators to open flood gates on water storage facilities, but the uncertainty of when Mother Nature’s faucet will shut off has experts weighing the advantages and disadvantages of letting the precious resource run free.
With recent storm systems that swept through the west, California has seen more precipitation this year than normal, bringing the water supply stored in reservoirs — both locally and across the state — up from historic lows to levels that are some of the highest in years.
And with drought conditions having improved in much of California, experts say that the amount of water captured from this year’s particularly wet winter could help ease the impact of hotter, drier weather in San Diego, as the state recovers its depleted water supplies.
Two winters’ worth of snow has already fallen in the Sierra Nevada since Christmas, pulling California from the depths of extreme drought into one of its wettest winters in memory.
But as a series of tropical storms slams the state, that bounty has become a flood risk as warm rains fall on the state’s record snowpack, causing rapid melting and jeopardizing Central Valley towns still soggy from January’s deluges.
