Don Pedro Reservoir:
Elevation: 809 feet, out of a maximum of 830 feet, as of Thursday
Tuolumne River watershed:
Snow course measurement: 141 percent of historical average for May 1
Precipitation: 36.39 inches, as of Thursday
If you’ve seen the Tuolumne River lately you may have noticed the water is swift and high. That’s due to lots of water being released from Don Pedro Reservoir to make room for incoming run-off from the melting snow pack.
Water was flowing at La Grange at a rate of 2,799 cubic feet per second (cfs) on Thursday but will be backed down to 2,100 cfs on Sunday. Operators are juggling the releases to ensure that Don Pedro has enough room to store the melting snow. As of Thursday, the lake’s elevation was at 809 feet in contrast to its maximum level of 830 feet.
“We anticipate filling this year,” said Jason Carkeet, a utility analyst with the Turlock Irrigation District. The last time Don Pedro was completely filled was in 2006.
Carkeet expects the river flows to remain high — possibly averaging 2,100 cfs — until the end of July. The water will run colder and faster than last year and present more of a hazard to swimmers.
“It’s going to be higher than it was last year,” said Carkeet, whose job is calculating water conditions above Lake Don Pedro each day to determine water releases through the dam. “It’s a complicated job.
“We know roughly how much water is up in the watershed. It’s hard to predict exactly how it’s going to melt off and come down. If it comes down really slowly, our release patterns will be different than if a lot of it comes down at one time.”
The minimum summertime flow will be 250 cfs which is much higher than the 50 cfs during the last three years of drought, said Carkeet.
TID started the rainfall season — running from July to June — on an iffy note. Early season runoff was not great but a wet spring made up for it all. The total anticipated precipitation for this rainfall season is 97 percent of normal.
As of May 1, the snow course measurement for the Tuolumne River watershed was 141 percent of what is a historical May 1 average. However, according to Carkeet, the entire precipitation record for the entire watershed is over 100 percent.
“There were times earlier this year when we were below average and recently we’ve gotten some good storms and that has put us up to average for the entire year to date,” he said.
Turlock Lake, another storage facility for TID, was at 236 feet this week and holding an estimated 31,766 acre-feet. An acre-foot is enough water to cover an acre one foot deep.
The total year-to-date precipitation in the watershed as of Thursday was 36.39 inches.