The 80 year old Corrales Siphon is in trouble yet again. Now the old, wooden pipe that delivers irrigation water to Corrales has a gaping hole near the Sandia Pueblo side of the river. It’s so serious that water may have to be pumped from the river directly into the Corrales Main Canal this spring and summer. The new chief engineer for the Middle Rio Grande Conservancy Distrct (MRGCD), Jason Casuga, contacted Corrales Comment January 27 to report that “a large sink hole was formed under the siphon on the east side of the river sometime after Christmas.
“As we explored the situation more, we concluded that it could only be from a hole in the siphon,” and that would mean that the Conservancy District will not be able to deliver enough water through the culvert to the Main Canal when irrigation season resumes.
Casuga said the likely solution would be to set up mobile pumps on the east side of the river to pipe water across the river for Corrales farmers to use.
“The damage to the siphon is likely to prevent the use of the siphon altogether. However, this does not mean that no water will be delivered to irrigators supplied by the Corrales Main Canal. The MRGCD and its consultants are currently exploring options for an alternative supply which include pumping water directly from the river into the Corrales Main Canal.”
Casuga has replaced Mike Hamman, who resigned at the end of December to become Governor Michelle Lujan Grisham’s senior water advisor. For several years, Hamman had warned that the old pipe was beginning to fail, primarily because it had been exposed to flowing river water once the river bed under which it had been buried since the 1930s was gradually washed away.
(See Corrales Comment Vol.XXXII, No.16, October 5, 2013 “River Bed’s Drop Disturbs Buried Irrigation Culvert.”)
But two years ago, the remarkable wooden stave culvert under the Rio Grande was apparently performing well after protective measure were undertaken.
That was the assessment by Hamman in January 2020. But high-water flows in the river caused erosion and undercutting of the river bank just south of the old Corrales Siphon, he reported.
“We are monitoring the siphon, and it is clear that what we did before certainly has stabilized the original exposed area,” Hamman explained. “We have noticed that some exposure of the frame above the pipe has occurred east of the stabilized section, and we are not too concerned at this point. But we are keeping a close eye on it.”
Hamman said the rip-rap installed along the west bank “performed well during the high and extended run-off, but just downstream of that area, the west bank is being undercut and eroding. The U.S. Bureau of Reclamation is aware of this problem, and will be addressing it under its work planning process.”
The 84 year old 1,000-foot wooden pipe has been buried under the river bed since the early 1930s but has been uncovered gradually by chronic erosion of the channel since upriver dams were constructed, reducing sediment deposited here.
When the problem was revealed more than ten years ago, the Middle Rio Grande Conservancy District implemented temporary fixes while trying to figure out what the real solution might be.
With assistance from the U.S. Bureau of Reclamation, the Conservancy District constructed a rock weir immediately downstream of the pipe near the west bank of the Rio Grande. “The MRGCD had previously had an inspection performed on the siphon and found that the wood pipe was in remarkably good condition with the exception of one missing wood stave in a section near the east bank,” Hamman said at the time.
The wooden culvert brings irrigation water from the east side of the Rio Grande to the west and into the Corrales Main Canal. Nine years ago, rapids began to appear where water flowed over the pipe.
An earlier MRGCD executive director, Subhas Shah, had explained to the mayor and Village Council that the uncovering of the siphon had been caused by a reduction in silt pouring into the Rio Grande after Cochiti and other dams were constructed upstream.
“In 1975 when Cochiti Dam was built, we started getting less silt coming into the river, and the river bed was getting eroded. So this is what we are seeing after 38 years.”
(See Corrales Comment Vol.XXX, No. 2 March 5, 2011 “So Far, River Bed Still Degrading Here.”)
The siphon is made of a series of 20-foot long by five-inch wide wood staves that are held together with steel bands to form a pipe that is approximately 900 feet long. It brings irrigation water conveyed through Sandia Pueblo under the riverbed and into Corrales.
In a statement January 29, Casuga added the following information for Corrales farmers.
“For the 2022 irrigation season, the Middle Rio Grande Conservancy District will have little storage water available and will depend on natural river inflows for irrigation deliveries. Considering water storage restrictions, poor climate forecasts, uncertainty in river inflows and a sizeable outstanding water debt to the Rio Grande Compact, the MRGCD is warning all irrigators to expect significant changes to irrigation delivery during the 2022 irrigation season.
“In addition to these conditions, it’s anticipated that water deliveries to the Corrales Main Canal, and the laterals and acequia fed by the Main Canal, will be significantly impacted due to the recent discovery of damage to the Corrales siphon pipe.
“The Corrales Siphon is the irrigation supply line for the Corrales Main Canal, bringing water from the east to the west side of the river through an underground pipe. The damage to the siphon is likely to prevent the use of the siphon altogether. However, this does not mean that no water will be delivered to irrigators supplied by the Corrales Main Canal. The MRGCD and its consultants are currently exploring options for an alternative supply which include pumping water directly from the river into the Corrales Main Canal.
“Please be assured that the MRGCD is taking all reasonable steps to find an alternative(s) to deliver water to affected irrigators.
“However, given these circumstances, the MRGCD strongly encourages irrigators served by these facilities to carefully consider all of these factors and their options when making farming plans for this season. If funding is approved by the State legislature during the current session, the MRGCD’s new Emergency Fallowing Program (EFP) will provide financial compensation for irrigators who voluntarily forego irrigation this season.
“Participation in the EFP, which is designed to lessen demand in times of lower water availability, will not impact your water rights.
“The MRGCD is pre-enrolling farmers on a voluntary basis in the 2022 EFP. If approved for enrollment and funding from the State is provided, participants will receive $425 per acre enrolled. Irrigators can access the pre-enrollment form by clicking on the “Enroll In The 2022 Fallowing & Leasing Program” button at mrgcd.com.
“For questions about the Fallowing and Leasing Program, contact Casey Ish at firstname.lastname@example.org or call him at 505-259-8799 after reviewing the enrollment form.
“For questions related to the siphon, contact Acting CEO/Chief Engineer Jason Casuga at 505-247-0234.”