From deep snows high on the crest of the Central Sierra to heavy rains down in Moccasin this month, the Tuolumne River watershed has soaked up 19.73 inches of water content so far in January, more than three times wetter than average.
The January total through Wednesday is also more than the historical five-month average for Sept. 1 through Jan. 31 in the Tuolumne watershed, which is 19.02 inches, said Calvin Curtin with Turlock Irrigation District, majority owner and operating partner of the Don Pedro Hydroelectric Project.
Don Pedro Reservoir was 91 percent full Wednesday, with 1.84 million acre-feet backing up behind Don Pedro Dam near La Grange, and the reservoir level was at 814.84 feet above sea level, according to the state Department of Water Resources.
Drawing it down
The last time Don Pedro was this full was in June 2011, Curtin said. Technicians at Don Pedro Dam were discharging 8,750 cubic feet of water per second Wednesday to make room for more storm runoff.
“We are letting water out of the reservoir as quickly as we can, as much as we can, for flood control,” Curtin said. “We’re restricted to keep it under 9,000 cfs. That keeps the river in its historic channel.”
Turlock Irrigation District staff started releasing water from Don Pedro in early January when they saw all the storms coming and the amounts of runoff being projected, Curtin said. The reservoir level at Don Pedro peaked this month at 814.92 feet on Tuesday.
“In the summer we can hold more water, we can take it up to 830 feet elevation,” Curtin said. “But right now we have to reserve space for flood control. We try to keep it around 801.9 feet and we’re drawing it down to that as quickly as we can.”
The next round of storms that could bring more rain and snow to the Mother Lode are not expected until sometime next week, Curtin said, and they are not expected to bring as much precipitation as the multiple series of storms that drenched the Central Sierra earlier this month.
As of Wednesday, instruments in Sonora has measured 17.4 inches of rain and water content from hail, sleet and snow so far this January, said Idamis Del Valle, a National Weather Service meteorologist in Sacramento.
The wettest January on record for Sonora is 1911 when 21.3 inches of precipitation was measured. The records go back to 1906 and they do not include the megastorms of January 1862, which generated the most devastating floods in Golden State history.
From Oct. 1 through Wednesday, Sonora has received 31.94 inches precipitation, more than double Sonora’s water year to date average of 15.09 inches, Del Valle said.
San Andreas has received 12.82 inches in January so far, and 24.28 inches since Oct. 1.
Boulders and mud
Barricades were in place Wednesday on at least two Tuolumne County roads damaged by storms earlier this month.
Boulders and mud have fallen in places on Italian Bar Road outside Columbia, and there’s more damage from washouts.
Fixing the west end of Italian Bar Road will cost a minimum $600,000 and that does not include recent damage in the Rose Creek area, Duke York, deputy director in charge of roads for Tuolumne County, said earlier this week. Another section of Italian Bar Road near Twain Harte that will cost another $200,000 to repair.
More boulders and washouts are evident on Marshes Flat Road in the September Marshes Fire burn area. The road is as steep in places as Old Priest Grade and fixing it will cost an estimated $1.7 million, York said.
A temporary bridge is still in place on Kewin Mill Road, which washed out two weeks ago when Five Mile Creek cut loose and severed a water main serving about 15 homes.
Residents of the Central Sierra foothills, including towns in the Sonora area, can expect overnight lows to continue in the low 30s tonight and rise to the high 30s this weekend and into early next week.
Daytime highs in the 40s to low 50s will continue through Friday, with slight warming into the mid 50s Saturday and Sunday.
Forecasters in Sacramento say the next chance of rain in the Sonora area and the rest of the Mother Lode is coming Feb. 1.