Streamflow outlook not looking any better
ALAMOSA — A week’s time only brought more warm weather and more bad news when Colorado Division of Water Resources Division 3 Engineer Craig Cotten presented the latest streamflow forecasts on Tuesday.
Division of Water Resources staffer Pat McDermott had delivered similar news the week before to the Rio Grande Water Users Association members during their annual meeting. Cotten did not have any better news on Tuesday for the Rio Grande Roundtable members.
“It’s not good,” he said. “Depending on who you listen to for forecasts depends on how bad it’s going to be.”
The Natural Resources Conservation Service (NRCS) is optimistically predicting about 61 percent of the long-term average streamflow on the Rio Grande, or about 395,000 acre feet, while the National Weather Service forecast is 39 percent of the long-term average at 255,000 acre feet. To some extent Cotten’s office is splitting the difference for a preliminary annual index flow for the Rio Grande of 350,000 acre feet or 54 percent of the long-term average.
Cotten said there is a big discrepancy between the NRCS and Weather Service forecasts, and he would like the NRCS forecast to be more accurate but believed the Weather Service’s forecast was probably going to be closer to the truth this year.
Likewise on the Conejos River system the NRCS forecast is 190,000 acre feet or 60 percent of the long-term average while the National Weather Service prediction is less optimistic at 140,000 acre feet or 44 percent of the long-term average. Again, somewhere in between is the Division of Water Resources’ preliminary annual index forecast of 170,000 acre feet or 54 percent of the long-term average.
Based on the division’s preliminary forecasts, the obligation to downstream states to meet Rio Grande Compact requirements will be 86,000 acre feet on the Rio Grande and 30,000 acre feet on the Conejos River system.
That water can be accounted for during the winter season, Cotten reported, meaning there should be no curtailments during the irrigation season to make those obligations. “We really shouldn’t owe much at all,” he said.
“That is the good news on that part, but it’s good news because it’s so bad,” Cotten added. There will be no curtailments because there will be no water.
“There’s a potential if we do go above that a little bit we will have some delivery obligation,” Cotten said. “Even if we go with NRCS numbers, it will be fairly low on both systems.”
It’s still not as bad as the drought year of 2002 when the index flow on the Rio Grande was 150,000 acre feet, Cotten added.
Some parts of the basin are in worse shape than others, Cotten explained, with generally less moisture in the northern part of the San Luis Valley than in the southern part, also less on the east side, Sangre de Cristos, than on the west, San Juans.
“It’s definitely not looking good for anybody but especially on the east side,” he said.
Even more bad news is the precipitation outlook for this spring (March through May), which is predicting below-average precipitation, Cotten said. By mid-summer, around July, the forecast calls for “equal chances” of average precipitation, he added.
“They’re calling for an average monsoon time period,” he said. “Hopefully later in the summertime we will get a little bit of moisture.”
With the warmer weather and lower forecasts, the water division office has permitted irrigation seasons to begin early in several parts of the Valley. The presumptive season dates are April 1 to November 1. The district permitted irrigators to begin drawing water in the drainage areas of Trinchera Creek on March 12 and La Garita, Carnero and Culebra Creeks on March 15. Several others will start next week.
“In the next few weeks we should have pretty much everybody on,” Cotten said.
The annual interstate Rio Grande Compact meeting this year will be held at the Texas capitol complex in Austin, Texas on Thursday, March 29. Cotten said the engineer advisors for each state met last week in Albuquerque to go over the compact accounting for 2017. The states do not all adhere to the same accounting method, but it appears Colorado ended 2017 with a debit of 300-400 acre feet, Cotten explained.