“NRCS does their best, based on the SNOTELs they have” — Steve Vandiver #RioGrande

NRCS Streamflow Forecast June 1, 2014
NRCS Streamflow Forecast June 1, 2014

From the Valley Courier (Ruth Heide):

Nobody’s crystal ball worked very well this year when it came to predicting river flows. In a Valley-wide water meeting yesterday, former long-time Division Engineer Steve Vandiver indicated the Natural Resources Conservation Service’s (NRCS) crystal ball might be cracked.

“NRCS does their best, based on the SNOTELs they have,” he said.

However, there are only about eight SNOTEL sites in the entire basin. SNOTEL is an automated system of snowpack sensors. Most of the SNOTEL sites in this basin provide information for the Rio Grande, with only two in the Conejos River system area. Vandiver said he was concerned about the apparent move by NRCS to rely on electronic data such as SNOTEL without confirming it through manual snow courses, a move that he believed would “lessen their ability to give us a good forecast.”

Vandiver added, “It’s vitally important we keep up with a forecasting system that means something.”

NRCS forecasts are the primary tool used by the Colorado Division of Water Resources Division 3 office to determine how much water the basin has to send downriver each calendar year and how much water irrigators will have available to them during the growing season. This year the NRCS forecasted annual stream flow for the Rio Grande at the beginning of the irrigation season was nearly 150,000 acre feet lower than the current forecast of 640,000 acre feet and the Conejos River system was almost 50,000 acre feet lower than the current forecast of 225,000 acre feet.

Because the earlier forecasts were off, the water division must send more water downriver now to make its annual obligation to the states of New Mexico and Texas as required by the Rio Grande Compact, Vandiver explained. That means an earlier cut off on the irrigation season on the Conejos River water users and greater curtailments on both the Rio Grande and Conejos River irrigators. Vandiver explained that because of the way the Rio Grande Compact was structured , the more water this basin receives, the higher percentage of it must be sent downriver, and the obligation percentage on the Conejos is already higher than the Rio Grande. In a big water year, which doesn’t happen very often , the Conejos system would have to send 70 percent of its water downstream, he said.

In normal water years, the basin has to send about a third of its water downstream to New Mexico and Texas.

“The delivery schedules dictate how much we can use,” Vandiver explained. Currently Conejos River system users are seeing a curtailment of more than 40 percent and the Rio Grande irrigators about 28 percent.

“On the Conejos system we are probably going to have to shut off early just to meet the compact,” Division 3 Engineer Craig Cotten said yesterday during the Rio Grande Roundtable meeting. He added the Rio Grande could probably make it to the first of November, the scheduled ending point for the irrigation season, but not extend past that point.

He said he will meet with Rio Grande irrigators before making the final decision on when to shut off the irrigation season this year. Vandiver, who held the division engineer position prior to Cotten and Mike Sullivan, described the headaches of managing water deliveries in the Rio Grande Basin (San Luis Valley) so that Rio Grande Compact deliveries are made and irrigators receive the water due them.

He said there are so many variables that affect runoff and stream flow every year from rain to dust on snow. He said NRCS has depended on various snow measurement sites around the basin through the years but has not had the funding and manpower recently to maintain, improve or increase those sites. When SNOTEL sites are not maintained, they are not able to provide accurate information for annual forecasts. For example, he said the SNOTEL site at Wolf Creek had problems ranging from large trees laying across it to a gopher hole in the middle of it that were not fixed before last winter, so the site did not work right, and it is one of the key sites in the SNOTEL system.

Conejos River irrigators are embarking on a $237,000 pilot project to use a portable radar system coupled with meteorological stations and river data collection sites to determine if there might be a better way to forecast runoff and stream flows in the basin, or at least to augment the information provided through NRCS. The Rio Grande Roundtable and state water board provided funding for that pilot project.

Nathan Coombs, manager for the Conejos Water Conservancy District that is spearheading this project, said it is not the group’s intention to influence or circumvent NRCS “We don’t need to pitch that aside and start over” but to collect data on a parallel track and see if it is useful for future forecasting efforts. Coombs said the best place for the radar truck to be set up would either be Antonito or at the airport in Alamosa. He added the radar coverage would provide information for both the Conejos and Rio Grande.

Cotten said his office is not mandated to use NRCS forecasts , “but there’s nothing else out there really.”

He added the weather service had started doing some forecasting.

“We are looking at their forecasts also.”

He said the NRCS and weather service forecasts were about 100,000 acre feet apart from each other this year, and it appeared the weather service’s forecast was closer to the truth this time, “which doesn’t always happen.”

Roundtable board member Cindy Medina suggested the roundtable or another group take the lead on presenting a package of basin snow measurement needs to legislators like Senator Michael Bennet who could work with NRCS to make sure funding is in place to meet those needs.

More Rio Grande River Basin coverage here.

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