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Major repairs to El Vado Dam next year will force New Mexico to look elsewhere to store irrigation water for the Middle Rio Grande Valley.
Page Pegram, the New Mexico Interstate Stream Commission’s Rio Grande Basin manager, said repairs should begin in the spring of 2022.
“That will leave El Vado Reservoir pretty much unusable (for storage) for at least a year, if not a couple of years,” Pegram said.
The reservoir has a total storage capacity of about 60 billion gallons.
A recent U.S. Bureau of Reclamation study said that the current dam, built in 1935 on the Rio Chama in Rio Arriba County, poses risks to the public.
“Seepage through the embankment, both through cracks in the steel faceplate and through the foundation of the dam, has led to high seepage losses,” the study said. “The steel liner of the service spillway has similarly deteriorated and is no longer safe to operate.”
The federal agency will fill holes in the dam and install a new liner. That first phase could limit the reservoir’s storage capacity to about 782 million gallons for a year.
Crews will then replace the spillway with concrete and build a new intake structure and control gate, which could limit storage to about 26 billion gallons until the project is completed.
Pegram said Abiquiu Reservoir is the most likely alternative for storing water during the reconstruction.
Cochiti and Heron reservoirs are not authorized to store native Rio Grande water for irrigation.
Abiquiu only recently was granted that authorization, with a provision included in the federal Water Rights Development Act of 2020.
El Vado storage water can be used to supplement river irrigation for the six Middle Rio Grande pueblos: Cochiti, Isleta, Sandia, San Felipe, Santa Ana and Santo Domingo.
But federal law prevents Heron Reservoir from “operating to satisfy (water) rights of Indian tribes,” so that reservoir would not be an adequate substitute.
The limited options to store water for next year’s irrigation season comes as New Mexico grapples with ongoing drought and the possibility of a warm, dry La Niña winter.
“Water supply conditions for the Middle Rio Grande in 2022, are expected to be significantly diminished,” Pegram said. “We expect streamflows in the basin to remain below average.”
Theresa Davis is a Report for America corps member covering water and the environment for the Albuquerque Journal.