Decreasing flow and unrelenting demand on the Colorado River
The solid lines in the graphs above show historical water use in the Colorado River system. (Source: When will Lake Mead go dry?, Tim Barnett, WATER RESOURCES RESEARCH, VOL. 44, 2008)
My previous post pointed toward continuing declines in the level of Lake Mead on the Colorado River. A commenter asked what my point was, and also whether there were any statistics on increasing demand on Colorado River water. This post attempts to answer those questions.
Although I wasn’t really making a point in my previous post, the implication was clear: Within a relatively short period of time, a large portion of the West could be running on empty, thanks to increasing demand on the river combined with decreasing supply.
According to a 2008 study published in Water Resources Research (subscription required for full text), Lake Mead already is being overdrawn by 1 million acre feet of water per year. Even assuming no decreases in runoff into the system due to climate change, the authors estimate that there is a 50 percent chance that Lake Mead and Lake Powell will both effectively go dry by the year 2037. If you take into account natural climate variability, and assume that climate change will reduce runoff by 20 percent, there is a 50 percent probability that this could happen as early as 2028. And there is even a 10 percent chance that mudflats will replace the reservoirs as soon as 2013.
Below is a graph showing probabilities of Lakes Mead and Powell reaching “dead pool” under different scenarios: no climate change, a 10 percent reduction in flow due to climate change, and a 20 percent reduction in flow:
Research by Martin Hoerling of the National Oceanic and Atmospheric Administration paints a very similar picture. “Our study reveals that a sustained change in moisture conditions is unfolding within the broad range of natural variations,” Hoerling writes. He says the Southwest is likely past the peak flows in the Colorado that occurred prior to the signing of the 1922 Colorado Compact, and that “a decline in Lees Ferry flow will reduce water availability below current consumptive demands within a mere 20 years.” That would mean dead pool by 2029.
I’m wondering how much sooner that day might arrive if consumption continues on its seemingly inexorable rise.