From InkStain (John Fleck):
Apparently in celebration of this week’s official release date for my book Water is for Fighting Over: and Other Myths about Water in the West, Lake Mead overnight crept above the magic elevation level of 1,075 feet above sea level. That’s number attached in policy and, more importantly, the public mind to the notion of shortage on the Colorado River. At this point the elevation milestone is merely symbolic. The shortage policy, with mandatory cutbacks, only kicks in if the reservoir is below 1,075 on Jan. 1 of any given year. Mead typically rises between August and the end of the year, so there will be no shortage declaration at the end of the year.
Don’t get too excited about rising above 1,075. We’re still on track to set another one of those “lowest elevation since Lake Mead was filled” records yet again this month. The end-of-August record low is 1,078.31 which we set last year. And as Brett Walton noted this morning in Circle of Blue’s Federal Water Tap, there’s a greater than 50 percent chance of a below-1,075 shortage declaration in 2018.
As a science-policy communicator, I’m fascinated with the way “1,075” has become such a useful shorthand for a complex set of issues. The origin of its importance lies in the 2007 “Interim Guidelines for Lower Basin Shortages and Coordinated Operations for Lake Powell and Lake Mead”. The rules are complicated: every year in August, the Bureau of Reclamation runs its Colorado River Simulation System (CRSS) model, a dynamic simulation that takes current reservoir levels, projected demands and forecasts for the coming months, and estimates the elevation of Lake Mead the following Jan. 1. That estimate (and an accompanying one for Lake Powell, the big reservoir upstream) triggers a number of policy responses. If there’s a bunch of extra water in Lake Powell, we enter one of a couple of operating regimes under which what I’ve come to call “bonus water” can be released from Powell to prop up Lake Mead, a process intended to “equalize” the levels between the two reservoirs.