Reservoir releases drive water levels higher in county rivers

STOCKTON — This has been the driest fall in San Joaquin County in more than a decade.

With that in mind, one might ask, why are our rivers so full?

Low-lying portions of the Calaveras River bike path were underwater this week. Farther south, on the Stanislaus River, the modest flows out of New Melones Lake are expected to periodically quadruple over the next couple of weeks.

The explanation for all of this is that upstream reservoirs are fuller than normal due to last year’s deluges. Despite the dry weather so far, and the likelihood that it will stay dry into mid-December, officials are releasing water from reservoirs to make sure there’s room to capture runoff from future storms.

Flows from Lake Camanche into the Mokelumne River have gone up from about 300 cubic-feet per second to about 1,300 cfs. That’s still considerably less water than the river was carrying last winter and spring, when it was close to 5,000 cfs for many weeks, a situation that caused flooding in adjacent vineyards.

Camanche is 69 percent full and 122 percent of normal. Importantly, there is little room this year to store water above Camanche, with Lake Pardee 99 percent full as of Friday.

Flows from New Hogan Lake on the Calaveras upstream of Stockton were holding steady about 50 cubic feet per second before climbing to more than 2,600 cfs earlier this week. That’s what dunked the bicycle path.

The water level at New Hogan has come down as a result; though at half-full, the reservoir is still 136 percent of normal and is technically holding a little more water than it is supposed to right now.

Flows from New Melones into the Stanislaus River are expected to climb from 600 cfs to as high as 2,500 cfs until Dec. 11, when flows will come back down again, the U.S. Bureau of Reclamation announced this week.

“People recreating in or along the Stanislaus River downstream from New Melones Dam should take safety precautions during the increased flows,” the agency said in a news release.

In a new forecast this week, the federal Climate Prediction Center said to expect drier than normal conditions across California over the next two weeks. The longer-term outlook is less certain, especially in Northern California.

The city has received less than an inch of rain all season. But this dry start might not mean much in the end.

Just look at 2005, when barely six-tenths of an inch had fallen in Stockton heading into the month of December. The rains came big-time starting in December, leading to flooding concerns well into April.