I’ve written in the past about the remarkable fact that, despite the 10 driest years on record on the Colorado River, no one’s had their allocation reduced or cut off.
The first plausible scenario under which that would change happens when the surface of Lake Mead drops to 1,075 feet above sea level. Under the 2007 shortage sharing agreement worked out among the US Bureau of Reclamation and the seven basin states, that’s the point at which lower basin states begin seeing reduced allocations.
The Central Arizona Project announced earlier this week that their hydrologists now calculate that there is a 15 to 20 percent chance of that happening in 2012:
[T]here is a 15-20% probability that in 2012, Lake Mead will have fallen an additional 13 feet to 1075’, triggering a declaration of ‘shortage’ on the Colorado River. Should the Secretary of the Interior declare a shortage, CAP, with the lowest priority to Colorado River water, would have its annual entitlement reduced by 288,000 acre-feet (93 billion gallons) or roughly 18 percent.
But, as the agency notes, “shortage” here does not mean CAP customers would actually see less water immediately. At this point, CAP officials say the immediate effect would be to reduce the amount of water available to the agency for groundwater banking.