Following five years of severe drought conditions, California is now in the midst of one of the wettest winters in recorded history - the effects of which can been seen locally in the Tuolumne River Watershed. So far in the 2017 precipitation year, which began in September, several months have already exceeded their historical averages, and last month proved to be no exception with over 15 inches of rainfall in the Tuolumne River Watershed.
This amount is nearly 10 inches more than monthly historical average of 5.99 inches for February. Last year, the Tuolumne River Watershed only received 1.59 inches of precipitation during the same time period.
February marks the fourth month that has surpassed its historical average this precipitation year. In October, the Tuolumne River Watershed received 5.96 inches of precipitation, which was 4 inches more than the historical average. December surpassed its historical average of 5.94 inches as well with 7.62 inches. In January, the region received more than 20 inches of precipitation, which marked a new record high for the month.
So far in the month of March, the Tuolumne River Watershed experienced 1.05 inches of precipitation, bringing the yearly total up to 53.04 inches. This amount is 203.6 percent of the region's historical average of 30.38 inches for the period between September and March.
"No news to anybody that it's been considerably wet," Utility Analyst Jason Carkeet told the TID Board of Directors Tuesday morning, March 8.
The hydrological largess seen locally can also be reflected in the Sierra Nevada snowpack, which continues to build during one of the wettest winters in California's recorded history. During a manual snow survey conducted by the Department of Water Resources at Phillips Station in the Sierra Nevada last week, officials found a snow water equivalent of 43.4 inches, which surpassed the March 1 average of 24.3 inches.
"It's not the record, the record being 56.4 [inches], but still a pretty phenomenal snowpack," said California Cooperative Snow Surveys Program Chief Frank Gehrke, who conducted the March 1 survey at Phillips Station. "January and February came in with some really quite phenomenal atmospheric storms, many of which were cold enough to really boost the snowpack."
During the first manual measurement in January, DWR revealed a dire snapshot of water content of the Sierra Nevada snowpack, which was found to be just 6 inches - only 53 percent of the early-January average. Nearly one month later, things began to look up as the February snow survey conducted at the Philips Station in the Sierra Nevada range revealed a snow water equivalence of 28.1 inches.
Snow water equivalence roughly equates to the amount of water that would hypothetically result if the entire snowpack suddenly melted. The snowpack on average provides about 30 percent of California's water once 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.
According to DWR's electronic readings from 98 stations throughout the Sierra Nevada last week, the statewide snowpack holds 45.5 inches of snow water equivalent, which is 185 percent of the March 1 average of 24.6 inches. On Jan. 1 before a series of storms, the snow water equivalent of the statewide snowpack was 6.5 inches, which was just 64 percent of the New Year's Day average. On Feb. 1, the statewide snow water equivalent was 30.5 inches, which is 174 percent of average for that date.
Additionally, water content came in at 39.2 inches for the northern Sierra snowpack, 49 inches for the central Sierra snowpack, and 46.4 inches for the southern Sierra snowpack. These readings are 159 percent, 191 percent, 201 percent of the multi-decade March 1 average, respectively.
Looking forward to the April 1 survey, Gehrke said that the central and southern regions in the Sierra Nevada are nearing conditions seen in 1983, a year which encompassed the maximum recorded snowpack statewide.
"Most of the snow courses are well over their April 1 accumulations, which at (Phillips) is 25 inches," said Gehrke, "so we've busted through April 1 values pretty much at all snow courses throughout the state."
DWR said that despite the above-average snowpack seen this year, many Californians continue to experience the effects of drought, and some Central Valley communities still depend on water tanks and bottled water. Groundwater - the source of at least a third of the supplies Californians use - will take much more than even an historically wet water year to be replenished in many areas.