Don Pedro managers doubt spillway will reopen

A second opening of the Don Pedro Reservoir spillway is unlikely this year, managers said Tuesday, despite a “staggering” amount of snow waiting to melt.

The prediction came at a meeting of the Turlock Irrigation District board, which approved a full allotment for farmers this year to help draw the reservoir down. The Modesto Irrigation District, partner with TID on the Tuolumne River, has similar plans for its customers.

The spillway opened Feb. 20 for only the second time in the 46-year history of Don Pedro. Managers did so because the reservoir was nearing capacity and the snowpack above stood at about 200 percent of average for the date.

The move caused moderate flooding in riverside zones on the lower Tuolumne and San Joaquin rivers. The spillway closed Feb. 27 at the order of federal officials concerned about Manteca-area levees, but flows are still much higher than normal.

It would take a very wet spring for Don Pedro to rise to the point where the spillway must reopen, said Wes Monier, strategic issues and planning manager at TID. Records dating to 1931 show some stormy periods at this time of year, but nothing of the magnitude that would fill the reservoir too quickly, he said.

The snowpack in the Tuolumne watershed stood at 186 percent of average as of Monday. The Don Pedro surface was at 813 feet above sea level, 17 feet below capacity.

Dry stretches in March have eased the concern, but the year is projected to still end up on one of the wettest on record.

“There is no (doubt) that the snowpack we have is staggering,” Monier said. “It’s huge.”

The board approved a 48-inch allotment to farmers, following five years of drought when deliveries ranged from 18 to 36 inches. That is 4 vertical feet over a season tentatively running from March 30 to Nov. 1. Wet weather could delay the start.

Farmers can buy water above 48 inches, which some crops and soil types could need. This also would help recharge aquifers stressed by the drought.

“We strongly encourage customers to flood-irrigate,” said Mike Kavarian, water distribution manager.

Many farmers have switched to drip or sprinkler systems to save water, but the flood method has strong support in agriculture because of the recharge benefit.

MID has returned to a full allotment of 42 inches and also is selling recharge water.

This story was originally published March 21, 2017 at 6:27 PM with the headline "Don Pedro managers doubt spillway will reopen."