A couple of years ago, I wrote about University of Colorado law school professor Doug Kenney’s argument that the states of the Colorado River’s Upper Basin (UB) faced a very real risk under climate change – that to the extent the river shrinks across the 21st century, the Upper Basin states will have the eat the shortfall:

If there are shortages on the river, New Mexico and the other states of the upper basin could be forced to curtail their water use, passing the water downstream for Las Vegas, Phoenix and Los Angeles.

“For a state like New Mexico, it means that satisfying current uses might be impractical, let alone thinking about new uses,” Kenney told me.

After I argued in a post yesterday that the new Colorado River Basin Water Supply and Demand Study suggests the real vulnerability to shortfalls is in the Lower Basin, Doug sent me this (posted with permission):

Even if the UB is able to meet its delivery obligation, that is very different from suggesting the UB is not experiencing any sort of shortage. Rather, making the delivery obligation ensures the UB is in a state of perpetual shortage (to the extent they never get their “half”). Thus, to the extent that the flow of the river is somehow enhanced, that could have UB benefits. In the short term, thus, this is a Lower Basin problem, but long term (especially under a severe climate change scenario), it is primarily an Upper Basin problem. The Lower Basin has some belt tightening to do, but it is a modest, predictable, and stable amount of belt tightening, whereas the problem for the UB just grows and grows.