Saturday, June 27, 2009

National Canyon

More beach details. A small sandy berm, and not too far away, a small eroding scarp.

The river rises and falls about once a day in the canyon -- a remarkably regular diurnal tide. But it's tied to the sun, not to the moon. When the sun shines on Phoenix and other southwestern cities, the air conditioners turn on and the power grid demands electricity. More water is allowed though the penstocks at Glen Canyon Dam and the flow in the Colorado downstream goes up. When it cools in the late evening, power demand falls, and so does the river. The resulting tide is generated at Glen Canyon, but it takes a day and half for the wave to travel down the river to Lake Mead.

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