Glen Canyon Dam
The Glen Canyon Dam is not one of the better known dams largely because it is overshadowed by its big brother. Built on the Colorado River upstream of the Hoover Dam it is only slightly smaller but not nearly as well known or widely visited. Nevertheless the Glen Canyon Dam plays an important role in controlling the flow of the river and in generating electricity.
The Glen Canyon Dam is on the Colorado River in Arizona where it was built to help resolve disputes over the use of the water of the Colorado River. There are seven states that the Colorado River passes through and they all rely on the water from the river. In the early twenties an agreement was reached between the states about how the water would be divided up. The problem was that in some years the water flow down the river fall to a low enough level that after the states that were up river used their allocation there was not enough water for the states that were down river. The solution was to build the Glen Canyon Dam to control the flow.
Of course if they were going to be building a dam anyway it made sense to include a hydroelectric plant so this was also included in the design. It took quite a while for the plans for the Glen Canyon Dam to be finalized as there was a lot of opposition from environmental groups. Nevertheless construction began in 1956 although it was not completed until 1966, the long construction period was largely the result of the disputes over the environmental impact.
The Glen Canyon Dam is a concrete arch dam that stands at seven hundred and ten feet tall. This makes it just slightly lower than the Hoover Dam for the tallest in the country. The reservoir behind it is called Lake Powell and it is the second largest reservoir in the US after Lake Mead which was formed behind the Hoover Dam. The Glen Canyon Dam nearly failed as the result of flooding in 1983. Had this happened it would have been a disaster as many cities along the river would have been flooded. Fortunately the dam held, although just barely and the floods never occurred. The near failure of the dam required that it be upgraded, in particular with new spillways being added.
The Glen Canyon Dam remains a rather controversial project even fifty years after being built. There are huge debates about the impact both good and bad that it has had. One concern that has become more of an issue in recent years is the loss of water from Lake Powell through seepage. This is the result of the porous rock on which it is built. Given current concerns about conserving water this has become an issue that a lot of people are worried about.