Dams

Many people have already dammed a small stream using sticks and mud by the time they become adults. Humans have used dams since early civilization, because four-thousand years ago they became aware that floods and droughts affected their well-being and so they began to build dams to protect themselves from these effects.1 The basic principles of dams still apply today as they did before; a dam must prevent water from being passed. Since then, people have been continuing to build and perfect these structures, not knowing the full intensity of their side effects. The hindering effects of dams on humans and their environment heavily outweigh the beneficial ones. The paragraphs below will prove that the construction and presence of dams always has and will continue to leave devastating effects on the environment around them. Firstly, to understand the thesis people must know what dams are. A dam is a barrier built across a water course to hold back or control water flow. Dams are classified as either storage, diversion or detention. As you could probably notice from it's name, storage dams are created to collect or hold water for periods of time when there is a surplus supply. The water is then used when there is a lack of supply. For example many small dams impound water in the spring, for use in the summer dry months. Storage dams also supply a water supply, or an improved habitat for fish and wildlife; they may store water for hydroelectricity as well.2

A diversion dam is a generation of a commonly constructed dam which is built to provide sufficient water pressure for pushing water into ditches, canals or other systems. These dams, which are normally shorter than storage dams are used for irrigation developments and for diversion the of water from a stream to a reservoir. Diversion dams are mainly built to lessen the effects of floods and to trap sediment.3 Overflow dams are designed to carry water which flow over thier crests, because of this they must be made of materials which do not erode. Non- overflow dams are built not to be overtopped, and they may include earth or rock in their body. Often, two types of these dams are combined to form a composite structure consisting of for example an overflow concrete gravity dam, the water that overflows into dikes of earthfill construction.4 A dam's primary function is to trap water for irrigation. Dams help to decrease the severity of droughts, increase agricultural production, and create new lands for agricultural use. Farmland, however, has it's price; river bottomlands flooded, defacing the fertility of the soil. This agricultural land may also result in a loss of natural artifacts.

Recently in Tasmania where has been pressure