Retiree Jerry Valentine, of Mountain Ranch, was fishing for trout Wednesday from his folding beach chair below Stevenot Bridge, where the Stanislaus River is impounded in New Melones, on the Tuolumne County side of the reservoir.
He said he had to move his chair every half hour because the water kept rising. Between 11 a.m. when he arrived and about 2:30 p.m., the water came up about 2 feet.
Warm storms this week are melting so much high-altitude Central Sierra snow and feeding streams so fast you can see the waters rise in giant reservoirs like New Melones. It was 46 percent full Wednesday, but it’s risen more than 45 feet since Jan. 10, and it’s the fourth-largest capacity reservoir in California.
So far, 2017 is one of the wettest on record in the Mother Lode, and dam managers on the Mokelumne, Stanislaus, Tuolumne and Merced rivers are dealing with runoff amounts and reservoir levels last seen in June and July of 2011.
On Wednesday, the Mokelumne River reservoirs — Pardee and Camanche — were 103 percent full and 63 percent full, respectively. Don Pedro on the Tuolumne River and McClure on the Merced River were close to 90 percent and 80 percent full.
Staff at Pardee, Don Pedro and McClure reservoirs are releasing rivers of water to make room for more storms.
Earlier this week, so much water was released from Oroville Dam on the Feather River in Butte County that a cavity opened on the lower reach of the spillway, and state Department of Water Resources staff shut down the spillway to investigate. They say the dam is sound, and no imminent threat to public safety exists.
No such damage has been reported at dams on the Mokelumne, Stanislaus, Tuolumne and Merced rivers. But massive amounts of water are still being released from Pardee, Don Pedro and McClure this week and into this spring, creating man-made, high volume rapids, whitewater and other potential hazards.
Don Pedro Reservoir on the Tuolumne River was 89 percent full Wednesday, about 4 feet higher in elevation than it was a month ago. The last time Don Pedro was this full was the summer of 2011, and the last time it was 100 percent full was July 30, 2011, Calvin Curtin with Turlock Irrigation District said.
The lowest level for Don Pedro in the past five years was 671.4 feet above sea level on Oct. 10, 2015.
Benefits of having the reservoir so full include available water for growers to irrigate crops, which also helps recharge groundwater, and increased generation of hydroelectricity, a clean and carbon-free source of energy that helps the environment, Curtin said.
Animals, fish and people were impacted during recent dry years, with impacts on humans including less water available for drinking, agriculture and recreation.
As of Wednesday, Don Pedro staff were releasing more than 8,150 cubic feet of water per second, equivalent in volume to more than 3.6 million U.S. gallons per minute. They need to bring the water level down about 10 feet from its current level, 811.75 feet.
“We anticipate high releases through April or so,” Curtin said.
McClure Reservoir on the Merced River was 78 percent full Wednesday and 31 feet higher than it was on Jan. 10. The last time it was 100 percent full was in 2011, said Mike Jensen, public and government relations manager for Merced Irrigation District.
The reservoir, which helps supply customers of Lake Don Pedro Community Services District, rose 8 feet overnight Tuesday, and it was expected to exceed 80 percent of capacity by Wednesday evening, Jensen said.
“So far, 2017 is the wettest year on record in terms of snowpack and precipitation,” Jensen said. “Merced Irrigation District is continuing to coordinate flood-management operations with the U.S. Army Corps of Engineers. As larger volumes of water reach Lake McClure from numerous recent storms, MID is increasing releases from the reservoir to provide space for storm and snowmelt runoff.”
Jensen is advising residents and boaters downstream to prepare for high flows of fast-moving water in the Merced River, up to about 5,000 cubic feet per second upstream and downstream of the Snelling area, and as high as 6,000 cubic feet per second this weekend.
High flow rescues
The last time such high flows were seen was 2011, the last wet year before five consecutive years of drought, Jensen said.
“The high flows in 2011 resulted in numerous water rescues on the Merced River after warnings of high water levels were ignored by boaters and rafters,” Jensen said. “Ultimately, access to the river was temporarily closed for public safety. Water flows at that time were approximately 4,000 cubic feet per second.”
High flows that began Wednesday are larger and faster than those of 2011. Jensen said Merced Irrigation District staff are maintaining contact with the Merced County Sheriff’s Office and the local Office of Emergency Services.
The low point for McClure in the past five years was in February 2015, when the reservoir held 63,390 acre-feet and fell to 585.97 feet above sea level. That’s about 6 percent of capacity.
“This year we have seen multiple high-peak flows on the Merced River from the winter storms,” Jensen said. “If not for New Exchequer Dam, and other dams like it, communities from Snelling to Stockton and beyond would have been flooded under unimpaired natural conditions of the Merced River and others flowing into the San Joaquin River.”
Looking ahead, benefits of the full reservoir mean Merced Irrigation District and its farmers have more surface water, they can turn off groundwater wells, and help recharge the local groundwater basin, Jensen said. Jensen also cited the ability to increase production of hydroelectricity, as well as more room for water recreation at McClure.
More weather coming
Dam operators are making room for more runoff in part because the next storm moves in this morning. This storm is expected to be a bit cooler at high elevations, and snow levels may drop to around 4,000 feet tonight from 8,000 feet Wednesday night.
From Wednesday to Friday, the Sonora area is expected to get an additional 3 to 4 inches of rain. Today and Friday, Ebbetts Pass on Highway 4, Sonora Pass on Highway 108, and Tioga Pass on Highway 120 could each get an additional 18 inches to 2 feet of snow.
Storm-related issues that continued in the Central Sierra on Wednesday included the closure of Bear Valley and limited operations at Dodge Ridge.
Intense rain, slush and snow had created unsafe conditions on slopes and roads at Bear Valley, a resort spokesman said Wednesday. All lifts were closed.
“With the amount of rain saturation in the snow pack, bonding has been the huge culprit here, or lack there of,” said Mattly Trent, director of guest safety and ski patrol at Bear Valley. “Think of the slushy drink at the fair and add 2 cups of water to it and that's what we have out on the ski hill.”
Dodge Ridge staff said they intended to open lifts including 1, 3, 6 and 7 on Wednesday, as well a children’s lesson conveyor.
Kewin Mill Road, which was closed Tuesday due to flooding, was reopened Wednesday morning. The closure temporarily snarled commutes for people who live higher on the hill in the Cedar Ridge area.
Recent rains and runoff have unleashed streams, cascades and cataracts in places not seen for several years, including one known as Peppermint Falls or Peppermint Creek Falls on Table Mountain in the Jamestown area.
An advisory for gusting winds is in effect until 4 p.m. today, and a flood warning is in effect until Saturday morning. Dry weather is expected to return by later Saturday.
Contact Guy McCarthy at firstname.lastname@example.org or (209) 588-4585. Follow him on Twitter @GuyMcCarthy.