Things occur in nature, that we as humans sometimes prevent from occurring naturally. For example – a dam on a river. Once put into use on a river, a dam simply stops or slows down the natural flow of the water. Sometimes this is for the better, however – sometimes, it is for the worse. This is the case in the Grand Canyon. Some rivers go through natural, periods of flooding and receding, at certain times of the year, or in occurrence with other geographical events. For the first time in thirty years, in March 1996, flood waters rages through the Grand Canyon. However, this was not the result of a natural flood.
The Colorado River would experience this same type of man made flood, naturally. These floods would occur every year during winter and spring rains. This water has been released from an upstream dam. The dam was put into action in 1963. Since then, years of environmental damage have been adding up. Dams have been on the river for nearly a century – however, none were upstream of the Grand Canyon until this one was built in 1963. Rivers have a number of processes involved in their everyday activities that allow themselves and the land around them to flourish. When the flow of a river is disrupted, so re these processes.
Rivers carry sediments. Along with carrying these sediments, they also deposit them, usually onto surrounding land areas. This deposition occurs when the flow of the water slows down. The amount of sediment a river is carrying generally gives color to its appearance. Before this dam was built, the Colorado River possessed a cloudy, rust color. Now, when the water is stopped at this dam, over 90 percent of its sediment is dropped. As a result – this gives the river a crystal clear appearance. Another result of the lack of sediment, is the beach erosion that is occurring.
Some beaches have eroded to over half of their original size. This erosion is happening because the beaches depended on the annual floods to bring them a continuous supply of fresh, fine sand. The dam is trapping a majority of the sand. There are small tributary rivers that flow uninhibited into the Colorado River below the dam, they bring some sediment – but not enough. As well as these beaches depending on the floods – the rapids in the river, have this same type of dependence. Here, the floods would clear any debris from between the boulders, an area that is now choked.
By 1989 – the public was concerned with the many problems facing the river and its ecosystems as a whole. A task force from Washington D. C. was sent into the canyon. Their conclusions revealed that the sediment being introduced by the tributary rivers, was settling along the bottom of the river, due to restricted water flow. At this conclusion – ideas sprang forth to open up the dam, and maybe try to reverse some of this decline. By opening up the dam, they could stir up some of the sediment sitting at the bottom of the river. By 1995 – they got the go-ahead.
In 96, the floodgates opened. This allowed 0. 7 trillion liters of water to bypass the turbines. The water flowed into the canyon at a rate of 1300 cubic meters per second, for a week. This was just under half the rate at which the river used to flood. After the flood waters cleared, researchers saw that the canyon was returned to a nearly pristine state. Instead of sediment laying at the bottom of the river – it had been piled high on the barren beaches. The most outstanding change was seen in the rapids of the river. Another flood is planned for this year, 2002.
