Dams
History and extent of Dams in India
- India’s first dam is the Kallanai built on the Cauvery river by King Karikalan of the Chola dynasty around 2,000 years ago. The dam, which is still functional and irrigates millions of acres, spans 329 m in length and 20 m in width.
- However, it was only post-independence that India’s love for big dams became more intense with the commissioning of a slew of projects including the Hirakud (1957), Gandhisagar (1960), Bhakra-Nangal (1963) and Nagarjuna Sagar (1967). Since then, the country has been continuously working on reining in its rivers for want of power, Irrigation and domestic and industrial water supply needs.
- Almost half of the large dams in the country were built in the two decades of 1970-90. Maharashtra has the maximum number of large dams in the country (1845) followed by Madhya Pradesh (905) and Gujarat (666).
- A multi-purpose dam project includes one or more dams, Infrastructure-2/”>INFRASTRUCTURE for generation of hydropower, infrastructure for housing of workers and for offices, a distribution Network of canals and pipe systems, and access roads.
- All these have their individual and cumulative impacts on the river and the surrounding Environment. Here also lies an opportunity to minimise the ‘collateral damage’ caused by dam projects by minimising the footprint of these adjuncts.
Dams as power generators
- Hydropower is often billed as a renewable, economic and non-polluting Source Of Energy and hence there is an increased emphasis on building dams especially in the hydrologically-rich but geologically-fragile Himalayan states.
- An assessment study put the hydroelectric power potential of the country at about 84,000 MW with maximum schemes envisaged on Brahmaputra basin (226) followed by Indus basin (190) and Ganga basin (142).
- Possibility of revenue generation through sale of power units to other states and private players remains the main draw for state governments to invite project developers.
- However, reports suggest that poor financial conditions of discoms make it a poor proposition. Average generation per MW of hydro capacity in India in 2014-15 was over 20 per cent less than that in 1993-94.
Dams and canals for irrigation
- Canal system of irrigation had been prevalent in India for centuries but it was the Ganga Canal that laid the foundation for large scale diversion of water to farms.
- Though the work was undertaken under the Leadership of British Colonel Proby Cautley, it was the traditional acumen of local villagers that made the vast network possible. The canal was commissioned in 1855 irrigating around 5,000 villages.
- Today, the system irrigates nearly 9,000 km² of agricultural land in 10 districts of Uttar Pradesh and Uttarakhand.
- The start of the Green Revolution in the mid 1960s put the spotlight on Canal Irrigation as the new hybrid crop varieties bred on heavy dose of chemical Fertilizers and pesticides demanded assured irrigation.
- However, the increased Investment and network expansion dealt little benefits.
- The World Commission on Dams in its year 2000 report found that the contribution of large dams to increased food grains production in India was less than 10 percent.
- Loss in seepage, huge demand-supply gap, diversions under political pressures and comparatively easier and local availability of groundwater through pervasive use of borewells are the reasons for decline in efficiency trend.
- Between 1996-97 and 2002-03, the area under canal irrigation declined by 2.4 million ha (13.8 per cent), the area under Tank Irrigation fell by 1.4 million ha (42.4 per cent), and the area irrigated by all other sources declined by 1 million ha (28 per cent).
- The only irrigation source that increased its share was groundwater wells, by 2.8 million ha (more than 9 per cent).
- A study of 210 major and medium irrigation projects by SANDRP used the data supplied by the Ministry of agriculture to show that after investing Rs 130,000 crore, these delivered 2.4 million ha less irrigation during 1990-1 to 2006-7. This means, the governments have to invest twice as fast in canal irrigation projects every year just to keep their command areas from shrinking
- The study said that around Rs 1,00,000 crore was wasted in the name of improving irrigation. Feasibility studies were fudged in the case of most of the projects with huge investments, over-optimistic predictions were made and very little Money was earmarked for basic maintenance such as desiltation. In some cases, political interests ensured that water was diverted to unviable areas at the cost of needier regions.
Dams and flood control
- The efficiency of dams to withhold floods has always been put to question. Critics have also termed dams as harbinger of floods claiming that the essential scientific assessment for consistent release of water to avoid build up is rarely done.
- Absence of a standard operating procedure for releasing water from the dam gates was evident in 2014 when 24 students picnicking in a river were swept away due to sudden release of water from Larji dam in Himachal Pradesh.
- Similarly, area downstream of Hirakud dam in Odisha has witnessed 14 floods in recent past with nine caused by sudden release of water from the dam.
- A major reason is that the dam has not changed its flood control strategy for 23 years while the rainfall pattern has undergone major changes in local areas.
- Lack of a coordination mechanism between neighbouring states about water flow also leads to emergency situations like one in 2011 when sudden release of water flow from upstream dams in Chhattisgarh led to breaching of danger mark in Hirakud.
- In Gujarat, sudden release of large quantities of water from Ukai dam led to the biggest flood of 34 years in Tapi river submerging over 80 per cent of Surat, killing 150 persons and stranding over 20 lakh. Similar examples have been reported from other states.
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Dams are artificial barriers constructed across rivers or streams to store water. They are used for a variety of purposes, including hydroelectric power generation, irrigation, flood control, and water supply.
Dam construction typically involves the following steps:
- Site selection: The first step in dam construction is to select a suitable site. The site must be able to withstand the force of the water, and it must be located in an area where the water can be used for the desired purpose.
- Excavation: Once a site has been selected, the next step is to excavate the area where the dam will be built. This includes removing any existing vegetation and Soil.
- Foundation construction: The foundation of the dam must be strong enough to support the weight of the water and the structure itself. The foundation is typically made of concrete or stone.
- Construction of the dam: The dam is constructed using a variety of materials, including concrete, stone, and earth. The type of material used depends on the size and purpose of the dam.
- Filling the reservoir: Once the dam is constructed, the reservoir is filled with water. The reservoir can be used for a variety of purposes, including hydroelectric power generation, irrigation, flood control, and water supply.
Dam safety is a critical issue, as dams can fail catastrophically if they are not properly maintained. Dam failures can cause flooding, loss of life, and environmental damage. Dam safety is regulated by the government in most countries.
Dam removal is the process of taking down a dam. Dam removal can be done for a variety of reasons, including safety concerns, environmental impacts, or to restore a river to its natural state. Dam removal is a complex process that requires careful planning and execution.
The environmental impact of dams can be significant. Dams can alter the flow of water, which can impact fish and other aquatic life. Dams can also change the water temperature, which can impact Plants and animals. Dams can also lead to the loss of wetlands and other important habitats.
Hydroelectric power is a form of energy that is generated by the flow of water. Hydroelectric power plants use dams to store water and then release it through turbines, which generate electricity. Hydroelectric power is a RENEWABLE ENERGY source that does not produce greenhouse gases.
Irrigation is the process of applying water to land to assist in the growing of crops. Irrigation can be done using a variety of methods, including flood irrigation, Sprinkler Irrigation, and Drip Irrigation. Irrigation is essential for agriculture in many parts of the world.
Navigation is the process of moving ships and other watercraft from one place to another. Dams can impact navigation by creating obstacles in the water. Dams can also change the water level, which can make it difficult for ships to pass.
Water storage is the process of collecting and storing water for later use. Water can be stored in a variety of ways, including in reservoirs, lakes, and aquifers. Water storage is important for a variety of purposes, including drinking water, irrigation, and hydroelectric power generation.
Water supply is the process of providing water to people and businesses. Water can be supplied from a variety of sources, including rivers, lakes, groundwater, and rainwater. Water supply is essential for human Health and well-being.
What is a dam?
A dam is a barrier constructed to hold back water. Dams are used for a variety of purposes, including water storage, flood control, irrigation, and hydroelectric power generation.
What are the different types of dams?
There are many different types of dams, but they can be broadly classified into three categories: embankment dams, gravity dams, and arch dams. Embankment dams are the most common type of dam and are made of earth and rock. Gravity dams are made of concrete or masonry and are designed to withstand the weight of the water they hold back. Arch dams are curved dams that are designed to withstand the force of the water by transferring the load to the abutments, which are the solid rock or earth on either side of the dam.
What are the benefits of dams?
Dams provide a number of benefits, including:
- Water storage: Dams can be used to store water for a variety of purposes, including drinking water, irrigation, and industrial use.
- Flood control: Dams can help to control flooding by storing excess water during periods of high rainfall.
- Irrigation: Dams can be used to irrigate crops, which can help to increase agricultural production.
- Hydroelectric power generation: Dams can be used to generate hydroelectric power, which is a clean and renewable source of energy.
What are the drawbacks of dams?
Dams also have a number of drawbacks, including:
- Environmental impact: Dams can have a significant impact on the environment, including disrupting fish Migration, altering water quality, and inundating wildlife habitat.
- Social impact: Dams can also have a significant impact on people, including displacing people from their homes and communities, and disrupting traditional ways of life.
- Economic impact: Dams can also have a significant economic impact, both positive and negative. On the one hand, dams can provide jobs and Economic Development. On the other hand, dams can also lead to the loss of jobs and economic opportunities.
What are the alternatives to dams?
There are a number of alternatives to dams, including:
- Water conservation: Water conservation can help to reduce the need for dams by reducing the amount of water that is used.
- Rainwater harvesting: Rainwater harvesting can be used to collect rainwater for a variety of purposes, including drinking water, irrigation, and industrial use.
- Desalination: Desalination is the process of removing salt from seawater, which can make it suitable for drinking and other uses.
- Wastewater treatment: Wastewater treatment can be used to treat wastewater so that it can be reused or safely returned to the environment.
What is the future of dams?
The future of dams is uncertain. Some people believe that dams will continue to be built, while others believe that they will eventually be replaced by other technologies. The future of dams will likely depend on a number of factors, including the availability of water, the cost of energy, and the environmental impact of dams.
- Which of the following is not a type of dam?
- Concrete arch dam
- Rock-fill dam
- Earth-fill dam
- Hydroelectric dam
- Dams are built for which of the following purposes?
- To generate electricity
- To provide water for irrigation
- To control flooding
- All of the above
- The Three Gorges Dam is located in which country?
- China
- India
- Brazil
- Canada
- The Grand Coulee Dam is located in which state?
- Washington
- Oregon
- Idaho
- Montana
- The Hoover Dam is located on which river?
- Colorado River
- Mississippi River
- Missouri River
- Rio Grande
Answers:
1. Hydroelectric dam
2. All of the above
3. China
4. Washington
5. Colorado River