Typically, dams provide a broad range of social, economic as well as environmental benefits. These include effective flood control, recreation, waste management, river navigation, hydroelectric power and perhaps wildlife habitat. This only implies that dams have proven to be extremely useful to humanity. In fact, studies tend to show that more than half of the world’s major rivers have functional dams constructed on them as a result of their anticipated benefits.
However, the construction of large water reservoirs has had significant negative impacts on the environment. To be more precise, it has completely altered between land and water, and this has led to the destruction of the existing ecosystem balance. There are over forty thousand large dams which obstruct the rivers globally thus changing their circulation systems. So today in this article, we want to examine in excruciating details, how dams affect the environment.
They negatively impact on the local fish population
The walls of the dam block the migration of fish. Now, this is perhaps because a significant number of dams lack adequate and efficient bypass systems. Again, the modification of dams upstream from an ever-flowing river ecosystem to an unfriendly slack-water habitat leads to temperature changes, increased chemical composition and increased levels of oxygen. These changes regarding the physical properties of a dam are often not suitable for both the aquatic plants and animals which may have evolved with a particular river environment. This will ultimately affect their life cycles, forcing certain fish species into extinction.
Increased incidences of soil erosion
Dams are known to hold back the silt deposition which would otherwise replenish the downstream ecosystems. When a river’s sediment load is held back, it will potentially design its own way to counter the problem. It will erode the downstream riverbed as well as the riverbanks. This will, in turn, cause significant damage to the available bridges as well as other riverbank structures.
Dams destroy the surrounding habitat and ecosystems
The construction of dams usually results in the creation of a reservoir upstream from the dam itself. This pool normally diverges into the surrounding ecosystem thus flooding the existing environment. These floods are known to displace or kill many organisms such as plants, humans and even wildlife.
It is also imperative to note that one of the primary reasons why dams are built is to help curb common flooding scenarios. However, the ecosystems that are prone to flooding are equally adapted to it. In fact, a good number of animal species largely depends on floods during their various stages of life cycle, including reproduction hatching. Again, floods transport and deposit nutrients downstream and this is disrupted by the construction of dams.
They can accelerate the spread of waterborne diseases
Also, the dams that are found in the tropical regions are ample breeding grounds for snails and mosquitoes which are the primary vectors of typhoid and malaria respectively.
They contribute to greenhouse gas emissions
Research has also revealed that most dams, especially those in the tropics, make a significant contribution to the global greenhouse gas emissions. The flooding of the surrounding environment kills trees as well as the other plant life in that area. The dead plants will then undergo decomposition hence releasing vast amounts of carbon into the atmosphere. The production and the subsequent emission of carbon into the air ultimately contribute to the global climate change.
Again, bearing in mind the river is no longer flowing efficiently, the stagnant water together with the decomposing plant remains to make the bottom of the dam to become depleted of oxygen. Subsequently, this lack of oxygen will make the decomposing plant materials to release methane gas, a very potent greenhouse gas which is then discharged into the atmosphere.
The Bottom Line
Despite the vast potential benefits that dams provide, they equally pose many harmful threats to the environment at large. These are just some of the negative impacts caused by them.