The dam is an important civil engineering structure that has paramount importance in various fields of engineering such as irrigation engineering, hydropower engineering and so on. The dam may be defined as a structure that is basically constructed to obstruct the flow of water or underground flowing water and streams thereby forming reservoirs that can be useful for supplying water for irrigation, industrial use, electricity generation, navigation, human use etc. Moreover, it can also serve as a protective structure for suppressing the flood. One of the main purposes of the dam is the diversion of water, retention of water and the control of water level.
Ever since the dawn of civilization in Mesopotamia and the Middle East, the man began to develop the concept of dam particularly for controlling the water levels in rivers. The earliest dam ever constructed dates back to 3000 BC and is located in Jordan. It is known as the Jawa Dam. With the development in engineering as well as an increase in the use of a dam, more than hundreds of dam has been built across the world. Some of the dam not only serves as an engineering structure but also serves as a centre of tourist attraction. Some of such fascinating dam includes Gordon Dam, Contra Dam, Monticello Dam etc.
Purposes of Dam
The dam is a multipurpose civil engineering structure that serves a wide range of functions. In today’s construction world, any work involving water resources inevitably consists of the construction of the dam either for raising the water level or for the storage of water. According to the recent reports of the World Register of Dams, about 48% of the dams are constructed for irrigation, 17% of the dams for the generation of electricity (hydropower), 13% of the dams for water supply, 10% of them for flood control, 5% of the dams for recreational purpose and about 1% of the dams are used for navigational works and fish farming.
The various purposes of the dam can be summarized as follows:
As discussed earlier, irrigation tops the list of the various purposes served by dams. At present, irrigated land covers approximately 18% of the world’s arable land and providing water for such massive areas of land is hectic and problematic. Due to the limited availability of water resources, the dam is usually constructed to retain water which can be duly utilized for irrigation.
Moreover, the total irrigated land produces only 40% of crops output which is not sufficient for the growing population. Hence, dams play a vital role in storing and providing water for irrigation throughout the world. According to the reports of the World Commission of Dam, approximately 30 to 40% of the irrigated land depends upon dams for the supply of water. Also, about 60% of the crop produced is dependent on the water provided by the dam for their irrigation. If dams are constructed and irrigation fosters, it will benefit the rural population and help to uplift their socio-economic condition as well. Thus, a dam can be regarded as the lifeline of irrigation.
For example, the Burrinjuck Dam is an irrigation dam located in Australia which was constructed as the main headwater storage for Murrumbidgee Irrigation Area in New South Wales.
Figure: Burrinjuk Dam, an irrigation dam in Australia
The generation of electricity by utilizing the water resources i.e. hydroelectric power generation constitutes about 24% of the world’s electricity. The combined capacity of hydropower plants throughout the world is roughly equal to 675000 Megawatts that produce 2.3 trillion kilowatts of electricity per year. Dams are an important component of such hydropower plants and are inevitable for the generation of hydro-electricity. Hydroelectricity constitutes about 90% world’s renewable energy which is produced utilizing the functions that a dam serves i.e. retention of water.
Some of the examples of dams that have been constructed for hydro-electricity generation are listed as follows:
1.Three Gorges Dam, China (installed capacity of 22500 MW)
2. Itaipu Dam, Brazil ( installed capacity of 14,000 MW)
3. Belo Monte Dam, Brazil ( installed capacity of 11,233 MW)
Figure: Schematic Diagram of Hydropower Plant
iii. Water Supply
The dam also serves the function of supplying water both for domestic use as well as for industrial use. The dam is an important structure that can be used for retaining the freshwater which can be used for human consumption and other domestic purposes. Water stored by the dam during the wet season can be very useful especially in the dry periods when there exists a high shortage of water. Likewise, the water stored by the dam can be utilized for various types of industrial works. One of the examples of the dam that has been constructed for water supply is:
1. Corin Dam, a water storage dam in Australia which has a capacity of 19.9*10 9 gallon.
Figure: Corin Dam, Australia (Water supply Purposes of the dam)
iv. Flood Control
Dams have been used as flood protection structures for centuries. It is an effective flood protection structure thus preventing loss of life and other damages. Since dams can regulate the level of water, the flood control dams impound the flood water and either release it to underground level or store it for the use in future or divert it away. Basically, flood control dams regulate the water level, store the water temporarily and release it later on. An effective integrated water management plan is prepared beforehand for such dams for the efficient regulation of storage and release of water without any subsequent damage. One of the prominent examples of such dam is The Tennessee Valley Authority Dams in the U.S.A. It was mainly constructed to help control floods on the Tennessee, the lower Ohio and the lower Mississipi rivers.
Figure: Schematic Diagram of Flood Control Dam
v. Inland Navigation
Inland navigation generally refers to the transport with ships through means of inland waterway such as water canals, rivers etc. The various water conditions such as fluctuating water level, changing rivers due to sedimentation and erosion etc pose a lot of difficulty in the inland navigation. To overcome such obstacles dams are built and they effectively serve the function of controlling the water level as well as changing the course of waterways thereby facilitating efficient inland navigation. Inland navigation is an important means of transport as they permit transport of a massive quantity of goods. Thus, effective inland navigation with a properly equipped system of locks, reservoirs and dam can boost the economic condition of the country. For example, the T.J O’Brien lock and dam in Chicago.
Several fascinating dams have been constructed throughout the world that attracts thousands of tourists every year. Dams also serve various recreational purposes such as boating, skiing, picnic, camping etc. Moreover, the water stored by the dam serves as the habitat for large species of flora and fauna. It also aids the growth of flora and fauna in the surrounding area thereby increasing the scenic appearance of the region. This has indeed proved to be one of the major sources of tourist attraction facilitating natural hiking, bird watching, landscape painting and so on. Such a rise in the recreational activities fosters the flow of economy in the country and thus helps to uplift the living standard of people. Some of the examples of such a dam can be listed as follows:
1. Springbank Dam, London
2. Mitchell Dam, Thames River
3. Centreville Dam, Southwest Oxford
4. Pittock Dam, Woodstock
5. Wildwood Dam, Trout Creek
6. Fanshawe Dam, London
vii. Mine Tailing
Another important function that a dam serves is mine tailing. Mine Tailing generally refers to the by-products that are obtained after any mining operation such as coal extraction, ore extraction etc. Such tailings obtained may be in solid, semi-solid or the liquid state. Since these tailings are highly toxic and potentially radioactive, the handling and storage must be done effectively. The by-products of coal, gold, copper and uranium also pose a great risk to the environment. An efficient way of storing such toxic by-products is the construction of mine tailing dam. Mine tailing dam is usually constructed by the earth-filled embankment. Thus, mine tailing dam can be
used for the storage of such products thereby mitigating the hazards.
Tailing dams are massive in structure and are ranked as one of the largest engineering structure in the world. Some of the examples of tailing dams that have been built across the world can be listed as follows:
1. Syncrude Tailings Dam, Canada
2. ASARCO Mission Mine Tailings Dam, U.S.A
viii. Other Purposes
In general, dams serve as multi-purpose structures. Primarily dams are used for hydro-power generation and irrigation and secondarily, used for water supply, recreational purpose etc. Besides these, the water stored by the dam can infiltrate into the ground thereby recharging the underground water bodies. Hence Purposes of Dam are many which bring immediate and dramatic benefits.