Rio Grande Basin: Water year recap

A picture named riograndebasin.jpg

From the Valley Courier (Ruth Heide):

[Chris Landry executive director of the Center for Snow & Avalanche Studies] and his team compared snow core samples to determine the number of dust events during a winter season. He reported an increase in dust events from 2008 to 2009 from 7 to 12 at the site studied in the Rio Grande Basin. The concentration of dust was heavier as well. In 2008 the concentration was 12 grams per meter while in 2009 it was 55 grams per meter. He said that is an enormous amount of material. “The San Juans in particular experienced the most dramatic advance in the state in snowmelt timing,” Landry said.

He said the reason for more dust might have simply been because this past winter was windier. He said not much data is available about the source of the dirt, presumably blowing in from the western desert. Landry said the dust layers on snow were fairly consistent statewide from Rabbit Ears Pass in the north to Wolf Creek Pass in the San Luis Valley.

The report from Division of Water Resources Division Engineer for Division III Craig Cotten bore out the fact that the snow melted off early this year. He told the water board the reasons for the early run off were probably dust on the snow and warmer temperatures in May. He showed graphs illustrating a dramatic decline in river flows in May. However, Cotten said irrigators were curtailed less than usual this year because of winter recharge and deliveries to downstream states. “We only had a month of curtailment on the Rio Grande this year,” he said.

On the Conejos system, curtailments were also zero during most of the run off period, from April 15 to July 9, Cotten said. The Conejos system went back to zero curtailment the end of August. He added, “We also had the entire suite of ditches in priority and diverting. The most junior priority on the Conejos system diverted for almost three months this year.”

Both river systems will likely over deliver the amount of water required by the Rio Grande Compact interstate agreement with downstream states. At this point Cotten is estimating an over delivery of 9,700 acre feet on the Rio Grande, about the same amount of water carried over in credit last year. He told the water board the ditches would be turned off October 31 under standard operating procedure but if the weather is warm the first part of November, water may run longer in order to recharge the Valley and reduce the amount of over delivered water downstream.

More Rio Grande Basin coverage here.

Leave a Reply