Drought news: ‘…short of 1,000-year events, rain doesn’t boost storage, it just maintains storage by easing demands’ — Chris Treese #COdrought

US Drought Monitor Colorado Map September 17, 2013
US Drought Monitor Colorado Map September 17, 2013

From The Grand Junction Daily Sentinel (Gary Harmon):

Rainstorms that pelted the West Slope while pounding the Front Range last week closed the major transmountain diversions that fed hardest-hit cities to the east. Stopping the diversions, however, isn’t expected to translate into significant storage increases on the West Slope after one of the driest winters on record.

Water managers on the West Slope “never count on rain to boost storage,” Colorado River Water Conservation District spokesman Chris Treese said. “If we had gotten East Slope volumes, we would have gained some storage — depending on location. But short of 1,000-year events, rain doesn’t boost storage, it just maintains storage by easing demands.”

“And likely more importantly, the soil moisture throughout the arid west received a huge bump,” Treese said.

The river has since dropped, though, and the call for the Shoshone generating station in Glenwood Canyon is back on. The water level of Lake Powell rose about two feet since the storm, or about 200,000 acre feet, Treese said. That’s less than 1 percent of the 26 million acre feet Powell can hold. The lake is about 44 percent full.

Even with the storms, storage on the West Slope is about where it would normally be at the end of summer, Treese said.

Front Range water managers were filling Estes Lake, which generally contains 97 percent water diverted from the West Slope through the Adams tunnel, entirely on runoff from the storms, Kara Lamb of the U.S. Bureau of Reclamation said.

Denver Water officials stopped diversions through the Roberts and Moffat tunnels but officials said they didn’t know how long the water would be shut off because those tunnels respond to calls from the South Platte River and customer demand.

Water officials shut down the Adams tunnel soon after the downpour set off alarms, warning officials with Reclamation and the Northern Water Conservancy District that Estes, designed to regulate the flows from across the Continental Divide, was being overwhelmed. Managers modified the way the system works “on this side to lessen the flood damage that would occur in Big Thompson Canyon,” Northern General Manager Eric Wilkinson said. Flood waters were shunted into Horsetooth and Carter lakes for a few days until debris closed off that option, “and we were unable to alleviate some the flows,” Wilkinson said.

Northern has two canals that showed considerable damage from the floods, but the district fared better than some ditch companies and other irrigators, Wilkinson said.

Some irrigation companies saw the bottoms of ditches scoured so deeply by the floods that the water now runs below their intakes, Wilkinson said.

Making repairs will take months, but, Wilkinson said, “We hope by winter to have the system back in fairly good order.”

Leave a Reply