Dammed if we don’t

 

Krista Langlois’ article “Busting the big one” (HCN, 9/4/17) aptly describes the existential dilemma of whether or not draining Lake Powell into Lake Mead would increase/maximize the amount of water available for human use.

If more studies are carried out to determine the best storage of available Colorado River water now and into the foreseeable future, I suggest that yet another variable should be evaluated and factored into any decision. Based on a well-documented geologic record, the possibility exists that a lava-flow dam may originate about midway between the concrete Hoover and Glen Canyon counterparts, restricting any “controlled” flow between the two. The probability of such an event taking place within whatever window of time is considered for the useful life of Hoover and Glen Canyon Dams is uncertain, but greater than zero.

About 20 lava-flow dams serially blocked the river in Grand Canyon during the past several hundred thousand years. Some of these were as tall as the Hoover and Glen Canyon dams; one was nearly 2,000 feet taller. The youngest lava dam was created about 100,000 years ago. There is no reason to conclude that yet another will not occur.

A key and presently unanswerable question is will this happen before Hoover and Glen Canyon dams have reached the ends of their useful lives. The youngest eruption in the river-neighboring area (Toroweap), where volcanoes repeatedly fed lava for the dams, happened only about 900 years ago. It begs the question of when will the next eruption take place. Planners for the continuing use of Hoover and Glen Canyon dams might be wise to include a lava-dam probability in the body of decision-making data.

Wendell Duffield
Whidbey Island, Washington

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