Valley to begin irrigation season soon
ALAMOSA—Water will soon start running in San Luis Valley ditches and canals.
The Colorado Division of Water Resources has announced irrigation seasons to begin as early as Saturday, April 1, and the Rio Grande Water Users Association on Thursday agreed to begin irrigating on April 6. April 1 is the presumptive start of the irrigation season in the Valley.
Division of Water Resources Division Engineer for Division 3 Craig Cotten shared with irrigators Thursday afternoon what the expected flow will be on the Rio Grande during the irrigation season and what kind of curtailment they would be facing initially to meet the demands of the interstate Rio Grande Compact.
The curtailment on irrigators associated with the Rio Grande will be about 19 percent at the beginning of the season, Cotten said.
He said at this point he is predicting an annual flow on the Rio Grande of 760,000 acre feet, which is more than the Natural Resources Conservation Service (NRCS) and National Weather Service are predicting. He said his office has been trying to use various sources to improve the annual forecast, and the weather service’s forecasts for the last couple of years were very helpful, but he believed their forecast at this point for the Rio Grande is about 200,000 acre feet off, “which is a lot of water. That makes a lot of difference to you guys.”
The weather service is forecasting 450,000 acre feet flow during the irrigation season, April through September, which would equate to about 550,000 acre feet for the annual flow. Last year the river produced 100,000 acre feet more than that, and this year is shaping up to be at least that productive, Cotten explained.
The NRCS is predicting 610,00 acre feet, or about 118 percent of average, flowing through the Rio Grande at Del Norte during the April-September irrigation season, which would be about 710,000 acre feet for the entire calendar year.
“I think they are a little bit low,” Cotten said.
He said he believes a more accurate prediction for the annual flow of the Rio Grande this year is 760,000 acre feet, of which 234,600 acre feet would be owed to downstream states to meet Rio Grande Compact obligations. With the amount of water that has gone downstream during the winter months and that will flow downstream after the irrigation season, the obligation required during the irrigation season will be about 130,400 acre feet, which at this point would require a 19-percent curtailment, according to Cotten.
The NRCS forecasts for other parts of the Rio Grande Basin range from 110 percent of normal on the Alamosa Creek at Terrace Reservoir to 160 percent of average on the San Antonio River at Ortiz. Cotten said river flows are anticipated to be higher in the southern part of the San Luis Valley this year than in the western end, “but everybody’s looking relatively good so far.”
Last year the Rio Grande experienced a good runoff with multiple peaks at fairly high flows, which meant a number of junior water users were able to take water from the Rio Grande in addition to senior rights. The river dropped off dramatically by July 1 of last year, however, Cotten added, and from that point on fluctuated above and below average.
Looking at a long-term history, Cotten pointed out that the last few years the Rio Grande has been very close or even a little higher than the average line of 640,000 acre feet.
“You have to go back to 2005 to get a year like we are predicting now, maybe just a little bit lower than that,” he said. “It’s not going to be a huge year, but it’s definitely going to be a good year this year.”
Snowpack so far this year is looking good, Cotten said.
“We are close to 18 inches of snow. The average is a little over 15.5 inches,” he said. “We are looking pretty good for now.”
He added that there was a drop about 10 days ago due to high temperatures, “and we did lose a fair amount of snow.”
He added, “We have gained it back with these storms coming through, but there’s definitely a lot of snow that’s ready to come out whenever we get another high temperature time period.”
Rio Grande Water Users Association member Carla Worley questioned Cotten about why the water stored in the Rio Grande Reservoir was not being used to meet compact obligations. Cotten explained that water is being stored in the reservoir in case it is needed to help meet compact obligations. Right now there is 5,000-6,000 acre feet of compact water in the reservoir with the intention to store about that same amount this year, he said.
“I am not sure if we are going to need it or when we are going to need it,” he said. He added one of the benefits of that storage water is to manage curtailments. For example, if it looked like the curtailment on irrigators was going to increase to 20 or 21 percent, the division could release some of the stored water to maintain the curtailment at 19 percent.
“Our ultimate goal is to smooth out the curtailment,” he said.
Worley asked if that could be a plan, rather than a goal.
“I would love to know exactly what’s going to happen,” Cotten said. “We don’t know for sure. That’s the plan.”
Assistant State Engineer Mike Sullivan added that in a big water year, with more water coming down the river, Colorado owes a greater percentage of that water to downstream states, so it is advantageous to have water in storage to send downriver to relieve the burden on irrigators.