Yes, you read the headline right. The heat wave that has hit the state this week is drying out everything in the Valley, but up in the mountains the high temperatures are causing a different problem: rapidly melting snowpack.
June snowpack runoff is extremely high, according to David Rizzardo of the California Department of Water Resources, with rates this year ranging from 109 percent of average (inflow to Shasta Lake) to 257 percent of average (Kings River).
For the Tuolumne River, the current runoff is around 19,000 cfs and averaging about 14,000 cfs for the month of June (237 percent of average). Normal June rates would be closer to 6,000 cfs. At this time last year, the Tuolumne River was running around 5,000 cfs or 82 percent of average.
“In general, this was one of our wettest years in terms of the amount of rainfall and snow that accumulated,” said Rizzardo. “For many rivers, it will also be one of the wettest if not the wettest in terms of overall runoff during the water year (from Oct. 1 through Sept. 30). And for this current snow melt period with the heat wave, runoff is obviously well average for the streams that flow into the San Joaquin Valley.”
Due to the high runoff, the Turlock Irrigation District has increased Tuolumne River releases from the Don Pedro Reservoir to accommodate water inflow to the Reservoir.
An elevation rise of the river of about four feet is expected to result from these staggered flow increases that began around midday on Wednesday, said TID Communications Manager Herb Smart. Releases at or near 9,000 cfs will most likely continue through Sunday.
"This operational change is a precautionary measure, is relatively routine given the snowpack runoff, and is in no way as concerning as the operations TID was forced to conduct in February of this year because of record precipitation," said Smart.
Generally, the water takes 24 hours to make its way to Modesto’s 9th Street Bridge, said Smart. For reference, flows at the 9th Street Bridge peaked at approximately 18,000 cfs this past February and peaked around 60,000 cfs during the 1997 floods.
Smart noted that this amount of water keeps the river well within its historic channel and will bring it to a level that is just above or near the National Weather Service’s ‘Monitor Stage’ elevation of 50.5 feet at the 9th Street Bridge. The weather service’s ‘Flood Stage’ elevation is 55 feet. There is no anticipation of utilizing Don Pedro Reservoir’s spillway, according to Smart.
While still under the ‘Flood Stage’, TID strongly cautions the public to use extreme care around rivers and waterways this weekend.
“It’s hot and the water is tempting but, it’s fast, cold and could be carrying debris and is extremely dangerous,” said TID spokesperson Calvin Curtin.
Due to historically high rainfall this past winter, TID opened one of three controlled spillway gates at Don Pedro Reservoir in February for the first time in 20 years as the water level reached past the reservoir’s maximum capacity of 830 feet.
The American Red Cross opened a shelter at the Stanislaus County Fairgrounds to assist those county residents living along the Tuolumne River who were displaced by flooding.