22 Positive and Negative Impacts of Dams on the Environment

Since the dawn of human civilization, dams have been built. King Seti constructed the first dam in 1319 BC. These historic dams continue to function and provide the essential water for cultivation and energy.

A lot of natural resources and materials are required for dam construction. There are also impacts of dams on the environment, which includes the aquatic world’s vegetation and wildlife. Let’s examine the environmental impacts of dams, both good and bad.

Let’s start with a few noteworthy facts:

  • Worldwide, there are between three and six times as many dams as there are rivers, according to the WWF. Over 50% of the wetlands were lost throughout the 20th century.
  • Out of the 10,000 freshwater species that have been recorded, more than 20% have recently gone extinct, become threatened, or are endangered.

These details are sufficient to demonstrate the enormous environmental impact dams are having.

Large-scale initiatives like dams are frequently proposed as crucial and essential tools for advancing the economy. However, this change has a price of some sort. cost to society, development, and the environment.

So what exactly do dams serve?

  • The availability of water for home use by the general people as well as irrigation is essential for our agrarian Indian society.
  • The production of hydroelectric power.
  • Dams obstruct the erratic and rapid flow of water to stop flooding.

That is what they are intended to achieve, and many of them do, but there is a lot of criticism and discussion surrounding them. A number of fervent national and international movements have made the serious issues connected to them more widely known.

Dams have drawn criticism for interfering with natural water flows, altering nutrient deposits, and changing the life cycles of species that depend on freshwater habitats.

Water salinity can rise as a result of water quantity reductions, making the water unfit for agriculture and consumption. Toxins can enter the environment as a result of organic matter decomposition and mercury leaching from the soil.

Sediment transfer, which is important for natural cycles, is also impacted.

This might increase the risk of flooding, lower groundwater levels, and have an impact on entire ecosystems.

Having said that, it is important to note that dams do not always harm habitats. For instance, if reservoirs are constructed, they may become habitats that are ideal for birds.

There have been certain instances where dam construction projects have had to pay a sizable fine for the environmental harm they caused in the beginning, although these instances are rare.


Environmental Impacts of Dams

When considering the environmental impacts of dams, we will look at the positive and the negative impacts.

Positive Impacts of Dams on the Environment

Recreation, flood control, water supply, hydroelectric power, waste management, river navigation, and wildlife habitat are just a few of the economic, environmental, and social advantages that come with dams.

1. Recreation

Dams offer top-notch leisure opportunities across the country. Dams provide the infrastructure for boating, skiing, camping, picnic places, and boat launch facilities.

2. Flood Control

Dams assist farmers and minimize the destruction of lives and property by the flood. Flood control dams hold floodwaters until they can be released into the river below the dam, stored, or diverted for use elsewhere. Dams have been constructed for thousands of years to help prevent catastrophic floods.

3. Mine Sludge

In the US, there are more than 1,300 mine tailings impoundments that enable the extraction and processing of coal and other essential minerals while maintaining environmental safety.

4. Debris Management

Dams can sometimes offer better environmental protection by preventing harmful sedimentation and the retention of dangerous pollutants.

5. Irrigation

For irrigation purposes, dams offer a reliable source of water. This is the main justification for building dams. The majority of nations rely on monsoon water because their water supplies are limited.

However, dam construction is considered necessary to provide much-needed water to the local populace due to abrupt changes in seasonal weather conditions. Any type of water scarcity that is not met by a deficient monsoon is combated by dams.

6. Provision of Drinking Water

There is still another justification for why nations support dam building. This is because the main source of drinking water is a dam. It offers the inhabitants year-round access to crucial drinking water. In some places, rivers quickly dry up because of insufficient precipitation, natural disasters like earthquakes, and exhausted water supplies.

As a result, dam construction is required to address water scarcity. The majority of the dams supply the local population with clean drinking water and energy.

7. Generates Hydropower

Another modern development by scientists is the use of dams to produce hydroelectricity. Dams can now be constructed to produce hydroelectric power. Water is forced through turbines at high pressure.

High-speed rotation of them as a result of it generates power. One dam has the capacity to provide enough electricity to run a small town for an entire year. Additionally, this energy is free of any hazardous fumes or greenhouse emissions. This makes it far more advantageous for a country.

8. Environmental Protection

By trapping harmful compounds in water and capturing silt that can contain poisonous or harmful materials, several dams contribute to environmental protection. Mine tailing impoundments are also present in some dams, which aid in the processing of minerals in an environmentally friendly way.

The nation’s waterways are made easier to navigate and less likely to experience accidents or other issues that could have a severe environmental impact thanks to dams.

Negative Impacts of Dams on the Environment

Dam construction has a variety of detrimental effects on the environment. A huge dam can have a wide range of negative environmental effects. It has a direct impact on the environment’s and rivers’ chemical, physical, and biological characteristics. Come learn more about them.

1. Harmful Effects on Aquatic Animals

Aquatic life is negatively impacted in numerous ways. Dams obstruct rivers and other flowing bodies of water, endangering any species that depend on the flow for reproduction or other aspects of their life cycle.

For example, migratory fish that mate in a region that is quite unlike where they spend the remainder of their life are unable to reproduce and may see a fall in population. Additionally, flowers that grow on the water’s natural border are at risk from the water’s accumulation. The vegetation can drown and perish.

2. Restricts Fish Migration

Fish migration is impeded by the dam walls, which separate spawning grounds from environments for raising fish. Additionally, silt, which is essential for preserving physical processes and habitats, is trapped. Maintenance of beneficial deltas, fertile floodplains, barrier islands, and other such operations are some of these procedures.

3. Altered Water Flow

The movement of silt and deviations in river flow have significant long-term effects on the environment. The amount and timing of a river’s flow determine the conditions for life inside. Marine life may suffer greatly as a result of altered or disrupted water flow. The ecology of a river can be loosened by little variations in the timing and volume of water flow.

4. Results in Inappropriate Survival Conditions

A dam converts a naturally occurring ecosystem into an unnatural one with slack water. It causes changes in temperature, dissolved oxygen levels, a reservoir’s physical characteristics, and its chemical makeup that are unsuitable for marine animal existence. Dams support invasive and non-native species like predatory fish, algae, and snails that disrupt the ecological communities of marine ecosystems.

5. Erodes River Beds

Downstream ecosystems will be organically replenished by the dam. It deprives a river of its sediment load and attempts to recapture it by corroding the banks and riverbeds. The groundwater table is lowered as a result of riverbed deepening, making it inaccessible to aquatic plant roots. Such changes to the riverbed reduce the environment for marine breeding species.

6. Sediment Accumulation Risk

Water that rushes through a dam’s internal turbines can trap and collect silt layers, which can contaminate the water and upset the ecology of the surrounding region.

7. Erosion of Surrounding Soil

There has been evidence of nearby land erosion following the construction of numerous dams. The huge reservoir of the Three Gorges Dam in China has damaged the shoreline in the area, causing landslides along the reservoir’s side.

Because of the decrease in sediment after the completion of the Aswan High Dam, the Nile Delta has experienced erosion. Since so much of the material washed into the reservoir, there is now less area available for farming and other activities.

8. High Cost & Disaster Risk

A dam can be built at astronomically high costs. Along with the physical construction, the engineering and technical parts require difficult, time-consuming work that must be completed with the utmost accuracy. The infrastructure of China’s Three Gorges Dam has already developed a few minor cracks due to its construction in a seismically active region.

An ultimate catastrophe would result from a dam breaking or collapsing, especially given the magnitude of the Three Gorges Dam. Huge floodwaters after Hurricane Harvey hit Texas pushed Houston area dams to their breaking point.

9. Impact on the Groundwater Table

Along a river, riverbed deepening will also drop groundwater levels, lowering the water table that plant roots can access (and human communities drawing water from wells).

The amount of formation has changed as a result of the building of the Dyke in Egypt. As a result of the increased humidity brought on by the shifting water table level, the damage is gradually being done to many of the city’s old structures as salts and harmful minerals are deposited within the stonework.

10. Greenhouse Gases

Dam-related habitat Flooding destroys nearby trees and other plant life, which then decomposes and emits significant volumes of carbon dioxide into the atmosphere. The water stagnates as a result of the river’s loss of free flow, depleting the oxygen in the reservoir’s bottom.

The decomposition of the plant matter at the reservoir’s bottom results in the production of methane, a particularly potent greenhouse gas, which is eventually released into the atmosphere and contributes to climate change on a worldwide scale.

11. Production of Methyl-Mercury

Because of the stagnant water in reservoirs, inorganic mercury can become methyl mercury when organic stuff from decaying plants breaks down. Sadly, methylmercury often accumulates in the body and has devastating consequences for people and animals who consume fish in reservoirs.

12. Negatively Impact Biodiversity

Dam effects are extremely dangerous for aquatic creatures, especially fish. According to Moran, biodiversity was lost by 70% as a result of the Itaipu Dam, which was built on the border between Paraguay and Brazil in the 1970s and 1980s.    

He said, “There was a 60% decline in fish productivity on the Tucuru Dam that was erected in the 1980s in the Amazon.”

In order to find food or travel back to their birthplaces, many fish species depend on rivers’ freedom of movement. Dams have a detrimental effect on migratory animals.

The International Union for the Conservation of Nature (IUCN) revealed in 2016 that over a period of three decades, catches of sturgeon and paddlefish, both of which are migratory, had decreased by 99%. Significant hazards to the survival of the species were listed as overfishing and river change.

13. Dams Lower Water Quality

Fertilizers that spill into the water from nearby land are captured in artificial reservoirs. In addition, in some developing countries, sewage flows directly into the reservoirs. This pollution can cause algal blooms that deplete the water’s oxygen content, making it acidic and perhaps dangerous to humans and other creatures.

In large man-made lakes, water has a warm top and a cold bottom, which can also have an impact on the water’s quality.

The cold water that is frequently released through turbines from the bottom of a reservoir may have harmfully high mineral concentrations, in contrast to warm water that encourages the growth of detrimental algae.

Sometimes the water in artificial reservoirs is in such poor condition that it cannot even be drunk.

14. Dam Wastewater 

Since a greater surface area of water is exposed to the sun, reservoirs cause a lot more evaporation than the river would have done naturally without the dam. According to estimates, the world’s reservoirs lose at least 7% of the entire amount of freshwater required for human activities each year.

In hot climates, this effect is exacerbated, Moran noted. “There will be a lot of evaporation,” he remarked, “if you have a reservoir in a tropical environment with high temperatures.” Additionally, large reservoirs “are of course continually evaporating.”

Additionally, weed-covered reservoir banks can result in evapotranspiration, or the transfer of water from the land to the atmosphere, by evaporation from the reservoir. Reservoirs are also a sanctuary for exotic plant species.

Six times as much evapotranspiration occurs as evaporation from the water’s surface. Furthermore, there is proof that dams encourage water waste by giving people a false sense of water security, which in turn leads to increased water use.

Some people wonder if the use of dams should be rethought in light of the world’s diminishing freshwater resources.


Dams must be regularly inspected and maintained if the environment is to be protected from their harmful effects. This will go a long way toward mitigating some of its negative effects, such as the widespread flooding that would result from a total dam failure.


Editor at EnvironmentGo! | providenceamaechi0@gmail.com | + posts

A passion-driven environmentalist by heart. Lead content writer at EnvironmentGo.
I strive to educate the public about the environment and its problems.
It has always been about nature, we ought to protect not destroy.

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