Some of the world's great rivers are at-risk of dying. Sixty percent of the world's largest rivers are already experienced the severe environmental impact of the construction of dams, canals, and irrigation systems. These structures have contributed to freshwater biodiversity in rivers worldwide.
Often these additions to the river benefit the locales economically and socially, but have seriously adverse effects on the environment. Water experts have fought to meet the safe water and electricity needs of the world's population. Dams have been used to solve some of these problems.
Due to the world's rapidly growing population and efforts to reduce poverty, dams have been built to provide access to safe drinking water and electricity.
Globally, there are more than 46,000 large working dams operational in more than 150 nations and these structures have impacted the biodiversity of those freshwater ecosystems. Large dams, some over 60 m. high are used for, irrigation, water supply, flood prevention, hydroelectric power, as well as multi purpose dams.
Dams have contributed to the economic needs of populations in the following ways:
1. making more land suitable for agriculture by supplying water for irrigation.
2. providing flood control
3. providing hydroelectric power for millions of people.
It must be recognized, however, that dams are also causing significant damage to the surrounding environments as well as reducing freshwater biodiversity.
Here are ways that large dams have negative effects on major rivers and their tributaries:
1. Dams alter the hydrology of the river and interfere with seasonal floodplains. Water is released to respond to man-made needs and this change to river flow can interrupt the life cycles of fish in the river.
2. As water quantity is reduced, so is the water quality. The resulting increased water salinity can render the water quality so bad as to create a situation in which the water can not be used for drinking or for agriculture.
3. As sediment is transported along the river, the form and structure of the riverbed, coastal deltas, and flood plain are disturbed. This results in a corresponding effect on the area's ecosystems. Sedimentation buildup can mean build up of toxins as well.
4. Dams can block migratory fish species from their spawning or feeding sites. Fish populations are severely affected by changes in water temperature and reduced water quality.
Changes upstream and downstream affect major rivers and their tributaries. Estuaries also experience this impact. As more large dams are built within close proximity of each other, the river basins are at risk and important habitats and species are vulnerable to damage or destruction.
Here is a list of some of the world's great rivers that are at-risk of dying due to human engineering of dams and other structures:
1)South America - La Plata Basin
After the Amazon River Basin, the The La Plata River Basin is the second largest basin in South America. This, too, is a high population area serving Argentina, Bolivia, Brazil, Paraguay, and Uruguay, including well over 100 million people. This basins three bodies of water are already undergoing physical change due to existing dams. More dams are being built and are planned for the near future.
2)Turkey, Syria and Iraq, Iran, and Jordan- Tigres and Euphrates Basin-
Desertification and water scarcity is a serious problem here already. Overall the basin is already very altered by dams and irrigation canals, and with the new dams planned upstream in Turkey, downstream water supply will be affected. With a total of 26 large dams under construction or planned in this area, there is reason to be very concerned about the possible loss habitats and their resident species.
3)China The Yangtze River Basin-
This is where so many of the larges dams are now and are under construction. is a rich centre for biodiversity, both terrestrial and freshwater, with well over 300 species of fish and nearly 175 species of amphibians.
This particular basin area also has an extremely dense human population demanding extensive amounts of fresh water and energy. The building of dams is increasing rapidly and many are well over 60m high. This is the area of the Three Gorges Dam.
With dam construction comes changes to species and habitats. For example, the baiji, or Yangtze River dolphin is at serious risk as shown by severely declining populations. Cranes and fish are threatened as are the people who make their livelihoods by the river basin.
4)India -The Ganga -
The sacred Ganga is suffering. Pollution, over-use of water, and climatic changes are killing the mighty river which supports over 8% of the world's population. The Ganga River Basin makes up almost a third of India's land area. Although pollution and uncaring consumption have contributed to its wasting away toward death, the damming of its tributaries for irrigation has seriously reduced its flow. This water scarcity is looking like a death sentence for its nearly 150fish species, 90 amphibian species and the endangered Ganga river dolphin.
5) China - The Salween River-
Dam construction poses the single greatest threat to the Salween River.China plans up to 13 large hydroelectric power plants that could lead to severe environmental damage.
Large dam projects have contributed to the economic needs of populations, but now the world must face the reality that some of the world's great rivers are now at risk of dying due to the environmental impact of these large dams.