TID closes spillway gate at Don Pedro but warns it may be needed again

A week after it opened, the spillway gate at Don Pedro Reservoir was fully closed just before 5 a.m. Monday, the Turlock Irrigation District reported. Based on the weather forecast of sunny days ahead, the district began the closure overnight, spokesman Brandon McMillan said.

TID, which manages dam operations, has returned to releasing reservoir water in the typical way, through the powerhouse, he said. The aim is to maintain the Tuolumne River level below the 55-foot flood stage as measured at Ninth Street in Modesto, McMillan said. The river flow should be about 10,000 cubic feet per second, he said.

When TID opened the controlled spillway Feb. 20 for the first time since the 1997 flooding, the release was 18,000 cfs. That night, it reduced the flow to 16,000 cfs.

Changes at the spillway take about 23 hours to be seen at Ninth Street, TID has said. On Monday morning at 11:30, the Tuolumne was at 58 feet, flowing at 14,4000 cfs. According to the National Weather Service’s Advanced Hydrologic Prediction Service, the river should be below flood stage by 8 a.m. Wednesday.

The river forecast Monday morning went through 4 a.m. Saturday, at which point the Tuolumne should be at 54.6 feet and flowing at 10,400 cfs.

TID’s goal remains to get the Don Pedro level to 815 feet, and then down to 801.9 feet, which is the preferred flood-control level based on the flood-control manual for the reservoir, McMillan said.

“It all depends on the forecast,” he said. “As things turn dry, it makes it easier,” though reaching just 815 feet will take weeks. Also, more than 2 million acre-feet of snowpack remains, he said, and any warm weather that begins to melt it also would determine the course of action by TID and the Army Corps of Engineers, which coordinates reservoir releases around the Central Valley.

“Our big request when we asked the corps to allow us to deviate (from the flood-control manual) was to continue releases at the level we were rather than close the spillway and have to open it again if conditions change,” McMillan said.

But on Friday, the corps denied TID’s request to keep the spillway open. It ordered the spillway closed to reduce the threat of flooding on the lower San Joaquin River, which is fed by the Tuolumne.

In a Don Pedro operations update Monday afternoon, TID said reuse of the spillway is likely in coming months. “It is extremely important to note that, to date, the Tuolumne River Watershed is experiencing the wettest year in recorded history and has accumulated more than 200 percent of average precipitation for this date. Snow sensors are recording a historic snowpack with potentially millions of acre-feet of additional inflow into Don Pedro when significantly warm storms or warm weather unfold in the coming months. ... Without adequate room in the reservoir, TID could be forced to use its controlled spillway again sometime this year.”

The Red Cross shelter at the Stanislaus County Fairground in Turlock, which has been housing people displaced by flooding, was scheduled to close at 3 p.m. Monday.

The nighttime manager at the shelter said Monday morning that 19 people had stayed the night. Red Cross officials said disaster caseworkers and California Social Services teams have met with the shelter residents to determine their needs and help them develop a plan for their recovery efforts.

The decision to close was based on close coordination between the Red Cross and Stanislaus County officials, the Red Cross reported. “While the flooding threat has diminished across much of California, the Red Cross urges everyone to stay ready for emergency evacuation,” it said in a news release. “That readiness includes maintaining a 72-hour evacuation kit, an evacuation plan, and staying informed about current conditions and evacuation notices.”

For more information about preparedness, visit www.redcross.org/prepare.

Though scattered showers fell in Modesto on Monday morning, there was no measurable rain downtown, Modesto Irrigation District data show.

The National Weather Service forecast is for sunny to mostly sunny days through Sunday. Beyond Monday morning’s light rain, there is no anticipated precipitation. The same is true for Sonora, except there’s a slight chance of rain Sunday.

In Modesto, Monday should be the coolest day of the week, with a high temperature near 58 degrees. The expected daily highs will increase to near 60 Tuesday, 62 Wednesday, 65 Thursday and Friday, and 66 Saturday. Sunday should be near 65.

This story was originally published February 27, 2017 at 8:02 AM with the headline "TID closes spillway gate at Don Pedro but warns it may be needed again."