Snowpack: Spring storms not enough to offset dry winter |

Snowpack: Spring storms not enough to offset dry winter

Sean de Guzman (right), chief of California Department of Water Resources snow surveys and water supply forecasting section and Andy Reising, water resource engineer, DWR snow survey section and water supply forecast section, conducts the final snow survey of the 2020 season Thursday at Phillips Station.
Provided / CDWR

SOUTH LAKE TAHOE, Calif. — The season’s final manual snow survey was conducted Thursday by the Department of Water Resources at Phillips Station near Sierra-at-Tahoe.

The survey recorded 1.5 inches of snow depth and a snow water equivalent of 0.5 inches, which is 3% of average for this location in May. The SWE measures the amount of water contained in the snowpack, providing a more accurate forecast of spring runoff than snow depth alone.

Measurements from the 130 electronic snow sensors scattered throughout the state indicate that the statewide snowpack’s water equivalent is 8.4 inches, or 37% of the May average. Thursday’s readings will help hydrologists forecast spring and summer snowmelt runoff into rivers and reservoirs.

“March and April storms brought needed snow to the Sierras, with the snowpack reaching its peak on April 9, however those gains were not nearly enough to offset a very dry January and February,” said Sean de Guzman, chief of DWR’s Snow Survey and Water Supply Forecast Section in a press release. “The last two weeks have seen increased temperatures leading to a rapid reduction of the snowpack. Snowmelt runoff into the reservoirs is forecasted to be below average.”

California’s weather variability has been on full display this water year. Dry conditions in October and November were followed by precipitation in December that measured 120% of average. Very dry conditions returned to much of the state in January and February, with March and April storms leading to the snowpack peaking at just 66% of average on April 9.

In normal years, the snowpack supplies about 30% of California’s water needs as it melts in the spring and early summer.

The greater the snow water equivalent the greater the likelihood California’s reservoirs will receive ample runoff to meet the state’s water demand in the summer and fall.

The state’s six largest reservoirs hold between 83% (San Luis) and 126% (Melones) of their historical averages for this date. Lake Shasta, California’s largest surface reservoir, is 94% of its historical average and sits at 81% of capacity.

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