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Science Frontiers ONLINE No. 116: Mar-Apr 1998 |
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An Anasazi Reservoir
In Morefield Canyon, Mesa Verde National Park, Colorado, a strange earthen mound, 200 feet wide, rises 15 feet above the canyon's grassy floor. Archeologists have debated the mound's purpose for decades. Being elevated above the floor of a usually dry canyon as it is, the mound certainly does not seem to be a reservoir, but that is what recent research says it is.
The mound is shaped like an inverted frying pan, with a 1500-foot-long handle that leads to a normally dry stream bed higher up in the canyon. The Anasazi were excellent water managers and took advantage of the flash floods that roared down the canyon every few years. To impound some of this valuable water, they initially built a conventional reservoir, but it was soon silted up by the freshets. So, they gradually raised the reservoir walls and constructed a raised canal to the stream bed. It was all very logical.
The engineering of the canal is particularly impressive. The channel is 4-8 feet wide, but only 1-2 feet deep. Its steep, 15-foot-high sides are shored up with neatly aligned stones that were carried in from somewhere outside the canyon.
(Anonymous; "Mystery Mound Appears to Be an Ancient Reservoir," San Francisco Chronicle, June 6, 1997. Cr. D. Phelps. Also: Anonymous; "Mysterious Mesa Verde Mound Turns Out to Be a Reservoir," Deseret News, June 10-11, 1997. Cr. S. Jones.)
Comment. The closely related Hohokam Indians built miles of well-engineered canals where Phoenix now stands. See SF#19 for description.