The Bureau of Reclamation’s announcement at Monday’s meeting of the Middle Rio Grande Conservancy District that it is halting work on El Vado Dam repairs raises hugely consequential questions about water management in New Mexico’s Middle Rio Grande Valley.

The short explanation for the halt is that the current approach to repairing the 1930s-era dam wasn’t working. (The meeting audio is here, though at “press time” for this blog post this week’s is not yet up.) I’ll leave it to others to suss out the technical and bureaucratic details of the repair project, and the endless finger-pointing that’s sure to ensue. My interest here is to begin to sketch out the implications here in the Middle Valley of an indefinite period – a decade or more? – without El Vado.

The Middle Rio Grande Conservancy District built El Vado (with substantial federal subsidy) in the 1930s to provide irrigation supplies by storing high spring runoff for use in summer and fall. But while its purpose was irrigation, it completely changed the Middle Valley hydrograph in ways that all the other water uses have adapted to, both human and ecosystem.

Without El Vado (or some interim replacement – see below), we should expect the Rio Grande to routinely go functionally dry in late summer unless propped up by monsoon rains, which are sporadic and unpredictable.

I see impacts in three areas, only one of which is related to El Vado’s initial purpose.

1: Irrigation

This is the obvious one. Until El Vado is repaired or some sort of replacement schemed out, irrigators should expect a high risk of low or no supply in late summer and fall. Alfalfa will remain a reliable if modest crop (it can hunker down and wait out the dry), but the few commercial operators who need a more reliable supply for their crops – think pecans and chile – will have to depend on groundwater, with all the problems that entails.

2: Municipal Supplies

Albuquerque’s use of its imported San Juan-Chama water in summer indirectly depends on El Vado. Without MRGCD water, released from El Vado, as “carriage water”, the Albuquerque Bernalillo County Water Utility has to leave its imported San Juan-Chama water parked in Abiquiu Reservoir, switching to groundwater. This is what we have done over the last few years, and our much-vaunted aquifer recovery has, as a result, stalled.

This poses a huge challenge for the Albuquerque Bernalillo County Water Utility Authority.

3: Environmental Flows

The idea of an agricultural irrigation dam providing the water for environmental flows seems super weird. But that’s basically the way it’s worked for years here in the Middle Valley. Releases from El Vado, sent downstream to irrigators, provide environmental benefits along the way. For the last couple of years, without El Vado water to supplement flows in late summer, the Rio Grande has operated on a knife’s edge between flowing and dry through Albuquerque.

This poses a huge challenge for efforts to nurse the Rio Grande silvery minnow back from extinction.

Storage alternatives

First and foremost, there is a fast-moving and scrambling discussion about storage alternatives.

Abiquiu Reservoir, a flood control facility on the Rio Chama built, owned, and managed by the U.S. Army Corp of Engineers, is an obvious replacement. The part in italics yields knowing nods, or perhaps grimaces, from folks who work in Middle Valley water management, because the Corps is well known for an exceedingly cautious interpretation of its statutory mandates. “Filling in as a water storage facility to replace El Vado” is only sorta barely at the edge of that mandate. Getting the Corps on board to help with this fix will be key.

Heron Reservoir, on a Rio Chama tributary, stores San Juan-Chama water imported through tunnels beneath the continental divide. It physically can’t replace El Vado because it’s in the wrong place. But discussions have already touched on the idea of doing it on paper via accounting swaps – hold back San Juan-Chama water, let SJC customers use native Rio Grande water via an accounting swap, then deliver Heron water as if it had been El Vado water.

Elephant Butte? Again, it’s in the wrong place, but accounting swaps here are also on the table.

Institutional Framework

The most important subtext is the institutional framework behind all of this. The loss of El Vado is not solely an MRGCD/Bureau of Reclamation problem. It implicates all the Middle Valley’s water stakeholders – especially Albuquerque’s Water Utility Authority, but also the Corps of Engineers, the Fish and Wildlife Service (because of ESA issues), the state water agencies, the communities on the valley floor that have avoided responsibility for any of this by depending on the state’s obscenely permissive domestic well statute.