Tuesday, March 3, 2015

Manual snowpack reading just 5 percent of normal

From the state Department of Water Resources:
The Sierra Nevada snowpack, which Californians rely on heavily during the dry summer months for their water needs, continues to disappoint this winter. Despite the snowfall in the Sierra Nevada Range over the weekend that gladdened ski and snowboard enthusiasts, it was not enough to offset weeks with no snow at all.

Today’s manual survey by the Department of Water Resources (DWR) at the Phillips snow course in the mountains 90 miles east of Sacramento found 0.9 inches of water content in the snow, just 5 percent of the March 3 historical average for that site. Electronic readings by the Department of Water Resources (DWR) today indicate the water content of the northern Sierra snowpack is 4.4 inches, 16 percent of average for the date. The central and southern Sierra readings were 5.5 inches (20 percent of average) and 5 inches (22 percent) respectively.

Statewide, 103 electronic sensors found today’s snow water equivalent to be 5 inches, 19 percent of the March 3 multi-decade average. When DWR conducted the season’s first two manual surveys on December 30 and January 29, the statewide water content was 50 percent and 25 percent respectively of the historical averages for those dates.

The snowpack’s water content this year is historically low for early March. Only in 1991 was the water content of the snowpack lower – 18 percent of that early-March average. Manual surveys of 180 snow courses this year reveal even less water content – just 13 percent of the early-March average, the lowest in DWR’s records for this time of year. The difference between electronic and manual surveys is explained by the higher elevation of most electronic sensors, where they receive more snow than many of the lower-elevation snow courses.

After records for dryness were set in many parts of the state in January, two storms in early February delivered enough precipitation at eight northern Sierra weather stations to bring the month’s total up to historical standards there. That short rainy interlude was followed by three weeks of virtually no rainfall in the northern Sierra, and precipitation at the eight stations since Water Year 2015 began on October 1 is now only 87 percent of average for that period. Further south, the 5-station San Joaquin index is 48 percent of normal, and the six-station index in the Tulare Basin is similarly far below normal at 51 percent.

Weeks of spring-like weather have produced more rain than snow when storms did arrive during California’s warmest winter on record. California’s historically wettest winter months have already passed, and it’s now almost certain that California will be in drought throughout 2015 for the fourth consecutive year.

Unless this month approximates the 1991 “Miracle March” with significantly more precipitation than normal, the traditional wet season will end on April 1 with an alarmingly low amount of water stored in the mountains as snow.

In normal years, the snowpack supplies about 30 percent of California’s water needs as it melts in the spring and early summer. The greater the snowpack water content, the greater the likelihood California’s reservoirs will receive ample runoff as the snowpack melts to meet the state’s water demand in the summer and fall.

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