The Sierra Nevada snowpack, a major source of water supply in California, has reached its highest level since 1995, raising hopes for an end to the drought but also concerns about the possibility of flooding due to rapid melting.
On February 1, 2023, the statewide Sierra Nevada snowpack was recorded to be 205% of its historical average, bringing hopes for an end to the drought in California. This is the third largest snowpack since consistent statewide records were taken in 1950 and is only surpassed by the years 1952 and 1969.1
The recent rise in the snowpack levels is due to a series of nine atmospheric river storms2 that hit the state starting around Christmas and continued for three weeks. Since then, temperatures have remained cool in the mountains, preserving most of the snow.
With the snowpack filling up, the state’s reservoirs are also beginning to fill up. The largest, Shasta Reservoir near Redding, is 56% full, or 87% of its historic average for that date. Meanwhile, Oroville Reservoir in Butte County is 65% full, or 112% of its historic average.
However, this surplus of snow has raised concerns about the potential for major flooding if a few warm spring storms hit the state. In 1997, several warm storms drenched the Sierra, causing the worst floods in Yosemite Valley in a century. Entire campgrounds washed away, half of Yosemite Lodge was destroyed, and several communities experienced major flooding when levees broke. The state declared 48 of California’s 58 counties as disaster areas and damage was estimated at $1.8 billion.
The ideal scenario for California would be to see a continuation of moderate storms, with dry spells in between, which will allow reservoirs to gradually fill up as summer starts and the risk of floods ends. Professor Jay Lund of UC Davis states that in a perfect year, reservoirs should be refilled by the end of May.
1 Sierra Nevada snowpack hits highest level in nearly 30 years – MediaNews Group – February 1, 2023
2 Endless onslaught of atmospheric river events in California claim 14 lives, residents urged to be hyper-vigilant – The Watchers – January 10, 2023
