Glen Canyon Dam

Human intervention was inevitable upon its discovery by the white man and has proved both helpful and harmful. Perhaps the most controversial alteration to the landscape was the Glen Canyon Dam which was constructed in 1963. The dam remains incredibly important for human sustenance in the desert, providing consistent water to Arizona, California, and Nevada. It operates in conjunction with the Hoover dam to keep consistent water available for the entire Colorado River Basin. It also produces much electricity for the Southwest grid, producing enough to power nearly half a million homes at its peak flow.

Despite the benefits of the dam, it has revealed to be quite damaging for the canyon ecosystem. The humpback chub has likely taken the hardest hit. The Colorado River, before the dam, fluctuated greatly in temperature and would regularly push mineral-rich silt along the river bed. Since the dam’s construction, silt deposits have eroded without being replenished and water temperatures have been regulated to about 48 degrees. Without this fluctuation, the humpback chub is put under high stress and also cannot adequately feed because of the lack of sediment. The previously muddy water is now clear. This has prompted the growth of algae (Cladophora), which feeds algae diatoms, which feeds worms, midges, flies, and the nonnative Gammarus (a crayfish like creature). Gammarus was introduced to feed rainbow trout, which were artificially introduced and stocked in the river, and sadly, feed on the humpback chub. Other species have not held on as long. The roundtail and bonytail chubs, the squawfish, and the razorback sucker have all been exterminated from the canyon because of these changes. Species like the striped bass and the shad, found in the western end of the canyon by Lake Mead, have also been hurt by lake of phosphorus in the water. To mitigate this, fertilizer has been added by Lake Powell in hopes of restoring needed nutrients.

Not all have suffered from the dam however. The dam has caused an influx of tamarisks on the river banks which provides habitats for various insects. There has been an increase in water bugs that feed insectivorous inhabitants of the canyon. This is great news for the peregrine falcon. At one time it was at risk of extinction because of use of the pesticide DDT. After it was banned and recovery measures were put in place, it was eventually reintroduced in the canyon. Today it thrives and is one of the more common birds in the park. The increasing number of bugs in the park means that riparian animals have taken advantage, such as Bell’s vireo or the southwestern willow flycatcher.

Boney Tail Fish (Humpback Chub), 1921
Emery Kolb Collection NAU.PH.568.5288
Researcher examining a sprig of tamarisk
John Running Collection NAU.PH.2013.
Grand Canyon Round-Up; Dams in Grand Canyon - a necessary evil?</br><a href="" target="_blank">P.T. Reilly Collection nm275g000s001b008f0112</a>
Grand Canyon Round-Up; Dams in Grand Canyon - a necessary evil?
P.T. Reilly Collection nm275g000s001b008f0112