Sierra snowfall that is the heaviest so far in 22 years has only been able to bring New Melones Reservoir up to 42 percent of its 2.4 million acre feet of water capacity.
The Department of Water Resources snow survey Thursday put the Sierra snowpack — the state’s biggest de facto water reservoir — at 173 percent of average for Feb. 2. More important, if it were to stop snowing and warm weather didn’t force an early snowmelt and accelerated evaporation, the snowpack is at 111 percent of normal for April 1.
The data on April 1 is the most critical for determining water deliveries for the coming 12 months plus to forecast whether there are adequate water supplies to meet commitments.
“Its great news,” South San Joaquin Irrigation District general Manager Peter Rietkerk said.
Rietkerk cautioned that it is still too early to make a final determination on water supplies for this spring, summer and fall given there is 56 days left until April 1.
New Melones Reservoir — that captures runoff on the Stanislaus River watershed that the cities of Manteca, Lathrop, and Tracy rely on as well as farmers in both the SSJID and Oakdale Irrigation District — is at the lowest level of the eight biggest state reservoirs.
It was at 42 percent on Thursday while nearby Don Pedro Reservoir that Highway 120 crosses on the way to Yosemite National Park was at 88 percent of capacity.
When it comes to capacity for this time of year New Melones is at 72 percent of average storage with almost every other reservoir in the state is in excess of 100 percent of average with Lake McClure topping the list at 151 percent.
Gov. Jerry Brown has indicated he intends to wait until after April 1 to determine whether to relax state mandates on water conservation.
Hydrologists and other experts have cautioned that one above average year — while it may fill reservoirs — will not erase the drought deficit. That’s because ground water has been inadequately recharged for the past four previous years.
The Sierra region that includes the Stanislaus River watershed averages 40.8 inches of precipitation based on annual readings at Calaveras Big Trees, Hetch Hetchy, Yosemite National Park headquarters, North Fork in Madera County and Huntington Lake. The weather year started with a 114.05-inch precipitation deficit from the previous five years. Before January storms hit, the average rainfall accumulated as measured by the five stations for the first three months of the water year that started Oct. 1 was 17.7 inches.
The latest specific region numbers weren’t available as of Thursday. However if it mirrors the state average there would still be at least a 44-inch precipitation deficit.
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