ALAMOSA — With the irrigation season nearly over, curtailments on Rio Grande irrigators are practically nil, while curtailments on irrigators on the Conejos River system are at 38 percent to make sure Colorado meets its Rio Grande Compact obligation to downstream states.
James Heath, assistant division engineer for Colorado Division of Water Resources Division 3, gave a report on the updated streamflow forecasts for the Rio Grande and Conejos River systems during Tuesday’s Rio Grande Roundtable meeting in Alamosa.
Due to record-breaking rainy periods this summer, the annual index flow forecast on the Rio Grande has been increased to 690,000 acre feet and the flow on the Conejos River system to 430,000 acre feet. With increased flow comes increased obligations to downstream states to comply with the Rio Grande Compact.
Heath said the Rio Grande has been able to meet those increased obligations, which amount to about 199,600 acre feet of that 690,000 acre feet total, due to good return flows. Because of that, the curtailment on the Rio Grande is only currently 1 percent.
However, 38 percent curtailment of irrigators on the Conejos River is required to make sure its compact obligation is met, Heath explained. Of the adjusted 430,000 acre feet streamflow projection for the Conejos River system, 214,000 acre feet must be sent downriver to meet the compact.
Heath shared the streamflow totals for the last few years for the irrigation season, April through September, which experienced an increase every year on the Rio Grande. During the irrigation season in 2014, streamflows were 518,630 acre feet; during 2015, 555,650 acre feet; during 2016, 565,800 acre feet; and during 2017, 573,860 acre feet.
The same held true on the Conejos River system. The Conejos at Mogote experienced a 30-percent increase in streamflows during the irrigation season (April through September) from 2016 to 2017, Heath pointed out. Streamflows on the Conejos at Mogote during 2016’s irrigation season were 180,350 acre feet, while this year’s season saw a flow of 241,730 acre feet. (The irrigation season streamflow for 2015 was 155,300 acre feet and for 2014, 149,300 acre feet.)
“A lot of late season rains have helped increase those flows,” Heath said.
Streamflows on Los Pinos near Ortiz almost doubled from last year to this year during the irrigation season and tripled on the San Antonio River at Ortiz, Heath added.
“We had a good year basin wide all the way through,” said Heath. He said while the past couple of years saw more snow in the northern part of the San Luis Valley, this year the moisture moved south. Rio Grande Roundtable Chairman Nathan Coombs, who is the manager of the Conejos Water Conservancy District, said this is the first year in the last seven consecutive years that the Conejos has had an above average year.
When Heath asked for input on when the irrigation season should end (November 1 is the normal season ending date), Coombs said he did not think the season should be extended on the Conejos at least. Heath encouraged input from water users on when they would like the season to end. The water engineer can extend the season past the presumptive November 1 date if he has good reason to.
Heath also shared precipitation and temperature forecasts from the National Oceanic and Atmospheric Administration (NOAA), which is calling for precipitation on the lower end for this area and temperatures on the higher end for the next several months.
Cleave Simpson, general manager of the Rio Grande Water Conservation District, said he remembered NOAA predicting hotter and drier for this year as well, and it looks like the Valley might log its wettest year on record.