Here’s how operator of Don Pedro Reservoir plans to guard against flooding along Tuolumne
The managers of Don Pedro Reservoir said they stand ready to handle the Tuolumne River surge expected with the next round of storms.
The Turlock Irrigation District said in a Wednesday news release that it has made careful releases since early January to prepare for runoff later in winter.
The massive dam near La Grange is designed to protect the lower 52 miles of river corridor from destructive flows from higher in the Sierra Nevada.
TID operates Don Pedro in partnership with the Modesto Irrigation District and has rights to about two-thirds of its water and hydropower.
The wet 2023 has allowed Don Pedro and other reservoirs to recover some of storage drawn down by three years of drought. But they can’t store all of it for future use. The winter releases make room for subsequent rain and for the snowmelt during spring.
The surface of Don Pedro sits at 830 feet above sea level when full. It was at 790 feet as of Wednesday, the California Department of Water Resources reported. It is required to go no higher than 802 feet this time of year under a state-federal system that coordinates reservoir releases.
The National Weather Service forecasts 3 to 5 inches of rain in Modesto through Tuesday. It has issued a flood watch through 10 a.m. Sunday. As much as 150 inches of snow — that’s more than 12 feet — could hit the Sierra Nevada watershed tapped by TID, MID and other agencies.
TID said its precautions also include recharging groundwater with releases from Don Pedro. This involves delivering water to farmers with well-draining soil, which allows it to seep down to the aquifer.
The district also noted that the water was released through the Don Pedro powerhouse. This allowed TID to rely less on generation from natural gas, which has shot up in price.
Flooding remains a possibility on Dry Creek, which enters the Tuolumne in Modesto, because it has no upstream dam. TID said it has been doing the Don Pedro releases in a way that leaves room in the river for a sudden burst from the creek.
Don Pedro has been overwhelmed only once in its 52-year history. Warm storms in 1997 caused major flooding in the Modesto area. The reservoir also had very high runoff in 2017, requiring several months of high but not damaging flows in the lower Tuolumne.
TID warned that the river will have similar conditions in 2023. It can be too fast for rowboats or swimmers even if it does not flood.
New Melones Reservoir is the main flood control on the Stanislaus River. It has even more unused space than Don Pedro because of its role in helping to sustain fisheries in the Sacramento-San Joaquin Delta.
Evacuation order along SJ River
Elsewhere in Stanislaus County, the Office of Emergency Services on Wednesday issued an evacuation order and an evacuation warning for the Newman area along a stretch of the San Joaquin River between Crows Landing Road and Hills Ferry Road. Both remained in effect Thursday.
According to a StanEmergency Facebook post, residents on the east side have been told to safely evacuate the area. Residents on the west side of the same stretch of river are under an evacuation warning and should be prepared to leave if it becomes necessary, county OES said
The San Joaquin is expected to reach flood monitoring stage by Friday afternoon. The monitoring stage, triggering levee patrols, is 63 feet, and flooding may start to occur at 69.4 feet.
According to forecasters, the river is projected to reach the 65-foot level Saturday night, at which a trailer park on River Road may start to take water.
Authorities set up an evacuation shelter at Patterson High School, 200 N. Seventh St.
Residents may call 209-552-3880 for evacuation information. Updated forecasts on the San Joaquin River level are at www.cnrfc.noaa.gov/graphicalRVF.php?id=NWMC1.
This story was originally published March 9, 2023 at 12:32 PM.
