other than supplying water, for what purposes dams and reservoirs be used?
Answers
A dam is constructed mainly for power generation, irrigation/water supply or flood prevention. However in most of cases dams have multiple functions. The main uses of a dam are presented below.
§ Power generation
Hydroelectric power is a major source of electricity in the world. Many countries have rivers with adequate water flow that can be dammed for power generation purposes. The reservoir water is stored at a higher level than the turbines, which are housed in a power station. Sometimes, the power station is directly in front of a dam, and pipes through the dam feed water directly to the turbines. In other cases, the power station is some distance downhill from the reservoir, and the water is fed to it through long pipes or tunnels called penstocks.
Diagram of Hydroelectricity plant (http://ga.water.usgs.gov/edu/hyhowworks.html)
§ Stabilize water flow / irrigation
Dams are often used to control and stabilize water flow, often for agricultural purposes and irrigation. Plants will grow naturally on fertile soil that is watered by rain. However, in regions of the world where the climate is very dry for some seasons, the soil becomes so dry that it restricts the growth of vegetation. This problem can be overcome by irrigation, a man-made system for watering the land.
Irrigation water can be stored in reservoirs during the rainy season, then in the drier seasons it can be released from the reservoir and distributed over the land through a system of canals. Usually, the water flows under the influence of gravity to the areas requiring it, or the water can be pumped out of the canals onto the land.
§ Flood prevention
Water from snow and rainfall will find its way into stream and rivers and eventually into the sea. After severe storms, or heavy snow or rain over a number of days, the water level in rivers can rise dramatically. Sometimes, the water flows over riverbanks or walls causing flooding of farmland, property, and in the worst cases, loss of life.
A reservoir can be used to control the amount of water flowing in a river after heavy rain. The water level in the reservoir is kept low during the rainier periods of the year. When heavy rain occurs, it is stopped by the dam and held back in the reservoir. When the reservoir gets too full, the floodwater can be passed downstream over a spillway. Sometimes, floodgates are used on top of spillways, and they can be fully or partly opened to control the amount of water let out into the river downstream. Dams such as the Blackwater dam of Webster, New Hampshire and the Delta Works are created with flood control in mind.
§ Land reclamation
Dams (often called dykes or levees in this context) are used to prevent ingress of water to an area that would otherwise be submerged, allowing its reclamation for human use.
§ Water supply of urban areas/ Industrial usage
Many urban areas of the world are supplied with water abstracted from rivers pent up behind low dams or weirs. Examples include London - with water from the River Thames and Chester with water taken from the River Dee. Other major sources include deep upland reservoirs contained by high dams across deep valleys such as the Claerwen series of dams and reservoirs.
1. It prevents from flood.
2. It maintains regular flow of water even in dry season.
3. People can practice Pisciculture.
4. It is used for hydel power generation.
5. It is used for supplying water for irrigation.
6. It used for supplying water to urban areas.