San Luis Valley: “We have had a good season so far” — Craig Cotten

Map of the Rio Grande watershed, showing the Rio Chama joining the Rio Grande near Santa Fe. Graphic credit WikiMedia.

From The Alamosa News (Ruth Heide):

Following record rainfall in July, water levels in area rivers have declined significantly, according to Colorado Division of Water Resources Division 3 Engineer Craig Cotten.

He said the annual streamflows on both the Rio Grande and Conejos River systems will wind up above normal, however, and the Rio Grande Basin (San Luis Valley) should have no trouble meeting its Compact obligations to downstream states.

“We have had a good season so far,” he said on Tuesday.

The basin experienced a good runoff, followed by a drop-off of flows and then above-average precipitation that bolstered streamflows, in some areas significantly, Cotten explained.

“We always anticipate precipitation in the monsoon periods, July and August time period, but the extent of that was a little bit unanticipated,” he added.

Streamflows in the San Luis Valley have dropped significantly in the last couple of weeks, Cotten said, on both the Rio Grande and Conejos River systems. The Rio Grande is currently below average for this time of year but should total about 700,000 acre feet streamflow for the year, which is above the average of 650,000 acre feet.

The Conejos River system should wind up with about 425,000 acre feet, which is well above the average of just over 300,000 acre feet…

Currently, irrigators are being curtailed 13 percent on the Rio Grande and 37 percent on the Conejos system, according to Cotten who said only three ditches with the highest priority are taking water on the Conejos River system right now.

Cotten said his goal is to meet the Compact obligation with some to spare but not over-deliver too much downstream…

With irrigation still ongoing, the Rio Grande Compact reservoir storage in Elephant Butte and Caballo Reservoirs in New Mexico has dropped below 400,000 acre feet to about 350,000 acre feet, Cotten explained. When that happens, reservoirs like Platoro Reservoir in the Valley that were built after the Compact went into effect cannot store water until the Compact reservoir storage in New Mexico exceeds 400,000 acre feet again. The storage prohibition will probably last until January, Cotten said.

Irrigation use is tapering off somewhat in the Valley for most crops except alfalfa, which is gearing up for a third cutting.

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