River Beat: Growing Bathtub Ring

Lake Mead, October 2010

Lake Mead, October 2010

To Emily Green’s monthly dirge to document as well as accompany the declining levels of Lake Mead, I would add this: Mead’s end-of-October surface elevation, 1081.94 feet above sea level, was 1.31 feet below the level forecast just a month ago.

Recall that 1075 is the trigger level for the first lower basin shortage declaration, and that, with a foot here and a foot there, pretty soon we’re talking about real water.


  1. As the lake drops, each 1-foot decline represents a smaller amount of water. How much water does a 1-foot decline from 1081 to 1080 msl represent?

  2. Francis –

    The rough rule of thumb folks use is about 100k acre feet per one foot elevation change. But you’re right, as the levels get lower, the number drops.

    I passed along your question to the USBR hydrology group. They sent me the table they use, which shows about 82kaf reduction from 1081 to 1080.

  3. Thanks. I hadn’t realized that there was so little (comparatively speaking) water in a 1 foot drop. It’d be interesting to see this in a graphic form — the Las Vegas Death Spiral, one might say.

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