A dam is a barrier that prevents or restricts the flow of water or groundwater. Dams have been used for agricultural, industrial purposes and domestic use for thousands of years. In this graphic article we’ll consider different ways dams and reservoirs help achieve economic, environmental and energy goals.

Dams and reservoirs have four main functions:

Dams and reservoirs hydroelectric power irrigation control flooding


Irrigation refers to the process of providing water for crops to meet their water needs. It provides water for growth, development, germination, and other related functions of plants. 30-40 percent of the lands that are irrigated globally rely on irrigation dams. Studies show that irrigation dams typically fail to reach the expected target because of the managing or engineering deficits. However, irrigated areas have increased from 70 to 100 percent for the past ten years.


Hydroelectric power

These dams can collect gravitational potential energy to provide a portion of needed electrical power. Around 19 percent of the electrical power supply worldwide comes from hydroelectric dams.

Most hydroelectric power generation comes from the energy of flowing water that drives turbines and generators, so basically, the power is extracted from the water current.


Most commonly, reservoirs are enlarged natural or artificial lakes created using a dam. Reservoir water can be used to supply water to our homes and factories, after it is sent to special treatment plants, to make it safe for drinking.

supply water


flood control

Reservoirs can prevent downstream flooding by maintaining and regulating the water flow during floods. They also balance water flow basedon weather conditions, by holding water back during heavy rains and releasing more during a dry spell.


Dams and reservoirs are created to provide a benefit to people, but they also can have a disastrous impact on our environment. People that live close to dams are especially impacted.

Environmental Impacts include:

Changing Aquatic Ecosystems

aquatic ecosystems

Building a dam in a river leads to vast changes in aquatic ecosystems, causing habitat loss, which is the biggest cause of extinction. Also, reservoirs can change the chemical balance and temperature of a body of water. These changes can make it less suitable for certain fish, which eventually leads to the loss of some of the species or enables predators to easily reach them.



Dams and reservoirs can decrease biodiversity of an area. As the flow of water decreases, sedimentation increases. Sedimentation is when particles that would normally flow through an area get caught in one place and settle in the water. Sediment can bury rock beds where fish lay eggs or cover up other important food and habitat features.

Greenhouse Gas Emission

greenhouse gas emission co2

The reservoirs cause rotting vegetation in the water. Through the process of decomposition, the greenhouse gases, methane, and carbon dioxide are released.



Open surfaces of the reservoirs speed up water loss by the evaporation process. Generally, much more water is lost from reservoirs than is lost from the flowing rivers they replaced. Increased evaporation can affect the microclimate and ecosystems of an area.

Seismic Activity

seismic activity earthquakes

Did you know that large dams can trigger seismic activity (earthquakes)? This is due to changes in stress of the weight of water, or increased groundwater pressure that decreases the strength of the rock under the reservoir.


Displacement Of People

Population displacement caused by dam and reservoir construction is the most serious social consequence. An estimated 80 million people worldwide have been displaced by dam projects and affected populations are rarely compensated after the displacement.

displacement of people population

Human Health Risks

Reservoirs are an ideal breeding ground for parasites, especially mosquitoes. These parasites spread disease to nearby areas and can create serious health problems.

Health risks Human health risks


The crucial steps that need to be taken to reduce the social and environmental impacts of dams include:

  • Demolition of an old dams and reservoirs
  • Increase the effectiveness of existing hydroelectric dams
  • Alternative energy research and effective usage of water in agriculture
  • Build new dams in an area where environmental and societal damage will be minimal

To sum up, ensuring that the construction of dams is in the least environmentally harmful areas will be hard, since the most environmentally friendly may not be the most economical.

steps to take dams reservoirs alternative energy research hydroelectric dams environmental social damage

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