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Rio Grande Basin still below average

Posted: Saturday, Mar 9th, 2013

Craig Cotten

Courier editor

MONTE VISTA — Dry may be the new normal for the San Luis Valley.

“We are having to adjust to a new normal,” Rio Grande Water Users Association Attorney Bill Paddock said during the water users’ annual meeting this week in Monte Vista, “not of the ‘80’s and ‘90’s but of the 2000’s when there is fundamentally less water. We don’t know when this will change.”

He added, “There’s nothing to be done about it but use less water … Until the weather pattern turns around we are going to have less supply, and it’s going to be tough.”

Paddock said the long-term average depends on what period of time is used. If the average is calculated from 1890 to 2012, the average annual flow of the Rio Grande at Del Norte would be about 650,000 acre feet. If the average is calculated from 1930-2012, it would be about 603,000 acre feet, and if the average is calculated from 1950 to the present, it would be about 593,000 acre feet annually on the Rio Grande at Del Norte.

Taking out extremely wet periods in the 1930’s makes a difference in what the “average” is, Paddock explained.

“We haven’t ever seen a river like that,” he said.

Paddock also pointed out that the five-year drought cycles appear to be getting more severe. The five-year drought from 1899-1903 averaged 482,552 acre feet on the Rio Grande at Del Norte, with the annual flows ranging from 393,400 in 1899 to 784,200 in 1903 and including a low year of 251,820 in 1902.

The five-year drought from 1950-1955 averaged 477,760 acre feet on the Rio Grande at Del Norte; the five-year drought from 1974-1978 averaged 471,813 acre feet on the Rio Grande at Del Norte; and the most recent five-year drought period from 2000-2004 averaged 423,930 acre feet on the Rio Grande at Del Norte.

Colorado Division of Water Resources Division 3 Engineer Craig Cotten said the initial projection for the annual index supply for the Rio Grande this year is 435,000 acre feet, currently estimated to be a little more than last year’s 407,000 acre feet. The 407,000 acre feet last year was about 66 percent of average for the Rio Grande, “definitely not a real good year,” Cotten said.

The 435,000 acre-foot estimate takes into account the NRCS (Natural Resources Conservation Service) irrigation season forecast (April-September) of 360,000 acre feet.

Of the estimated annual index of 435,000 acre feet, the Rio Grande will have to deliver about 25 percent or about 107,800 acre feet downstream to New Mexico and Texas to meet Rio Grande Compact obligations. Because of winter flows sent downriver prior to the irrigation season and expected to be delivered after it ends this fall, the curtailment on the river during the irrigation season will likely be about 12 percent, Cotten told Rio Grande Water Users Association members on Tuesday.

“Last year we started off at 10 percent,” he added.

The amount of curtailment on irrigators depends on multiple factors including the turn-on date for the irrigation season, Cotten said. He has not yet decided when that date will be for the Rio Grande. The presumptive irrigation season is April 1 to November 1. Senior water users are recommending April 10 as a turn-on date, and the Rio Grande Canal water users would like water turned on as soon as possible.

Last year the irrigation season began March 29 and ended November 1.

Colorado Division of Water Resources Deputy State Engineer and former Division 3 Engineer Mike Sullivan said the longer irrigators can wait to begin running water, the more water can be sent downriver now and the less curtailment will be required during the main irrigation season when farmers need it the most.

The goal for meeting the Rio Grande Compact is to get as close to the obligation as possible without under or over delivering. In 2012 the state over delivered, primarily due to the Conejos River system. The Rio Grande under delivered, but the Conejos more than made up for it, so Colorado ended up with a surplus of about 6,400 acre feet in compact water. Cotten said that number has not been ratified or accepted by the compact commission, but he hoped that would occur during the annual meeting in Alamosa on March 21.

Cotten reported the snowpack on the Upper Rio Grande Basin as of March 5 was about 78 percent of normal.

“Currently we are a fair amount lower than we should be, than the average, lower than we have been the last three years,” he said.

He said to reach average snowpack would require 189 percent moisture from now on.

“We are hoping we will still get some snow,” Cotten said. A storm is predicted for this weekend, for example.

“Hopefully we will get to where we were last year and hopefully higher than that.”

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