I was reminded at a talk last night that farmers in the Elephant Butte Irrigation District in southern New Mexico got less than 10 percent of a full irrigation allotment last year.

I say that by way of a preface to noting Juliet McKenna’s observation that there’s a 50-50 chance of a formal shortage declaration in the Lower Colorado River Basin in 2016. We’ve already heard a lot about the risk of the Colorado River’s first shortage, and we’ll hear a lot more. But it’s worth remembering that lots of arid climate water users, especially in the ag sector, deal with shortages with some regularity. This is only interesting on the Colorado River because it’s unprecedented. As I’ve pointed out before, in the midst of the worst drought in the instrumental record, everyone in the Lower Basin has gotten a full allocation, every single year.  The notion of the sort of rock solid, reliable 100 percent allocation is the exception rather than the rule in arid climate western irrigation.

The impacts of a Colorado River shortage declaration will be modest compared to what many arid climate irrigation systems cope with routinely as a result of climate variability.