Tempe Town Lake Drain

July 12, 2010

Tempe Town Lake is an artificial reservoir on the Salt River (Rio Salado) where the river flows through the city of Tempe, Arizona. The reservoir was created through the use of inflatable dams—rubber-coated tubes of strong fabric affixed to concrete slabs. As part of a flood-prevention program, the computer-controlled tubes could be inflated or deflated, depending on water levels. On the evening of July 20, 2010, however, one of the dams burst, draining the reservoir and sending water down the Salt River.

The Thematic Mapper on NASA’s Landsat 5 satellite captured these natural-color images of Tempe Town Lake on July 12, 2010 (left), and July 28, 2010 (right). The difference in water level is most apparent near the west end of the reservoir. In the July 12 image, the lake’s west end is a uniformly thick band of water. By July 28, after the sudden draining of the lake, the west end of the reservoir appears as a thin, meandering stream and a few disjointed pools.

By early 2010, authorities had noticed that some of the rubber on the inflatable dams was deteriorating, and replacement was scheduled to begin in February 2010, said local news reports. A severe winter storm, however, forced the postponement of repairs as the dams had to be deflated to accommodate a storm surge on the Salt River. Officials explained that water flowing through the dams prevented immediate replacement. After the dam burst on July 20, Tempe’s mayor stated at a press conference that reconstruction had already been scheduled to start on July 21. He described the timing of the dam breach as fortunate because, had the dam burst after repairs started, the event would have endangered repair crews.

The construction of Tempe Town Lake is just the most recent in a long pattern of human engineering along the Salt River, according to a timeline compiled by AZCentral. Native Americans are believed to have built an extensive canal system on the river as long ago as 500 AD. Much more recently, a “lakeside amusement park,” complete with an artificial lake, was constructed in 1949 on Tempe’s section of the Salt River, but seepage apparently caused the lake to dry up the following year.

NASA images by Robert Simmon, based on Landsat-5 data from the USGS Global Visualization Viewer. Caption by Michon Scott.

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