A dam is a huge barrier-like construction built over surface of flowing water systems. More commonly dams are built on rivers but are not limited only to them. They can be constructed on streams and estuaries also. The purpose of construction is to hold back water and retain it for future uses. When the river is obstructed to flow by a barrier, it creates massive water storage on the upstream side generally referred to as a reservoir. Dams have floodgates that can be opened or shut so that only limited flow is allowed for human usage.
Gates also allow the release of excess water from the reservoir side during floods. When a river floods up, there is an excess accumulation of water on the reservoir side. The flood gates are cautiously opened to release excess water. This is the main purpose of dams. They prevent floods, saving the lives of millions.
It takes about a decade to construct a dam, while a well-maintained one can persist for 100 years serving its purpose throughout its lifetime.
Dams have multiple uses aiming for human benefits on a wide scale.
Dams have become the main source of irrigation for crops in recent times. In tropical countries like India, the rainfall is confined to a limited period of the year.However, agriculture runs year-round and requires water for farming based on the growth stage. While some crops like rice and sugarcane need excess water. Irrigation made agriculture possible in distant regions even in those with low underground water levels. .
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Dams are a great source of Electricity.
The floodgates are opened and water from the reservoir (already at high pressure) is allowed to flow over the turbine that is connected to the generator.The kinetic energy of water is converted to mechanical energy by a turbine which is further converted to electrical energy by a generator.Hydroelectric power can be generated when there is a need for electricity. Otherwise, the water can be used for human consumption or agricultural needs.
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Reservoirs are a great place for recreation. Many reservoirs provide the local people with camping, boating and fishing facilities.
Humans never failed in being masterminds. Investing crores of rupees and lots of energy in building dams has several advantages.
Dams generate hydroelectric power which is not dependent on any fossil fuel. Hence, hydroelectric power is a renewable source of energy and can be used without fear of exhaustion. A growing population has an ever-increasing demand for energy. Hydroelectric power is one of the safest ways to meet the energy crisis.
Reservoir maintains a large deposit of water that serves primarily for storage of fresh water which can be used later during conditions of water scarcity.
The reservoir water can be used for irrigation. Croplands at large distances can be well irrigated. The irrigated farmlands are a source of food production.
With the growing population, there is an alarming rise in drinking water demands also. Reservoirs provide water for basic human needs in areas near to as well as those lying far off from the dam. With depleting groundwater resources and uneven rainfall, the increasing demands of industrial as well as domestic purposes are met by water from reservoirs.
Dams prevent floods by diverting their flow. The cautious release of water from reservoirs through floodgates saves thousands of lives and prevents property loss also.
The reservoir is a hub for multiple aquatic species like fishes and turtles. The construction of dams makes the flowing river into a lake habitat. The freshwater fish and turtle species take the chance to raise their numbers, converting it into a lake ecosystem.
Although dams have a multitude of advantages to human life, there are a set of disadvantages also.
Construction of the dam involves digging out deep layers of earth to make a strong basement and reservoir. This disturbs the topography of the earth. This causes an increase in the frequency of earthquakes. However, such devastation can be prevented by efficient planning, design and engineering.
Dams are huge concrete structures. Their construction is not a cost-effective process.
The construction of dams requires a large area. The local farmers and people inhabiting the areas need to be relocated to other places. This has an impact on their social as well as economic lives with long term consequences.
Apart from displacing people, there is much more disturbance to the natural habitat. Deforestation and loss of fertile farmlands are major points of concern regarding flora affected by dam construction.
Natural fauna inhabiting the dam area is also deranged at large, sometimes even posing a threat to their population. The breeding grounds and nesting areas are essential places to maintain their populations. These places, when disturbed by other elements, obviously show an impact on their numbers.
Apart from the terrestrial and aquatic species, bird species are also disturbed. Migratory birds that nest on river beds feed on fishes inhabiting freshwaters. Since dam construction leads to a severe alteration in aquatic life, migratory birds lose their feed and cannot breed as they do in every season.
Few species of fish migrate to freshwater systems for spawning. Since the construction of the dam disturbs the upstream as well as the downstream path of the river, it is a threat to migratory fish also.
Deepening the river bed to build reservoirs causes a lowering of the groundwater table in surrounding regions. This greatly impacts adjoining natural vegetation that does not depend on irrigation. For example, large trees need to develop a deep root system to reach the depleted water table.
Although hydroelectric power is a renewable source of energy, the hydroelectric power associated with dams is reported with slight greenhouse gas emissions.
Dams are huge concrete constructions built on surface-flowing rivers for human benefit. It is a laborious process to construct a dam. It needs a massive investment of money. There are plenty of benefits provided by dams. Majorly accounting for their efficiency to prevent floods and becoming a major source of water supply for domestic and industrial applications, dams hold a special place in the present era. Apart from the benefits, there are also some potential disadvantages since they cause disturbance to natural vegetation.
Q1. Do dams have a lifespan?
Ans. It takes about a decade to construct a dam and they live for nearly 100 years. After 50 years of constructing a dam, certain mechanical elements like motors and gates need to be replaced. However, dams in operation will be inspected periodically. Any repairs and maintenance will be done immediately whenever required. If dams are not repaired on a timely basis, the risk of breakage during floods may arise which can lead to a severe loss of lives and property.
Q2. Can we depend on hydroelectric power as the sole source of electricity?.
Ans. Hydroelectricity is a renewable source of energy. The fact that water will not deplete is true since the water cycle is not disturbed in the process associated with the dams. But the limitation is that dams need flowing water which is confined to rivers and streams. Sustainably produced energy from hydroelectric power cannot serve as a sole source of energy. The construction of dams may lead to severe geological changes on earth which may trigger earthquakes.
Q3. How are dams associated with greenhouse gases?
Ans. Building a dam floods large areas of vegetation, immersing several trees in the water. Stagnant waters in reservoirs have low oxygen levels at the bottom. These biomass rich bottom layers of the reservoir add an efficient amount of methane (formed because of decomposition) into the environment. Methane is a potent greenhouse gas accounting for global warming and climate change.
Q4. How are farmers benefited by dams?
Ans. Reservoir stores large quantities of water which can be used for agricultural purposes by irrigation. Croplands in semiarid regions far off from the river bed can also be well irrigated. Farmers do not have to depend on rainfall for farming. They can plan a year-round cropping pattern with the storied waters of the reservoir.
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