The United Nations Institute for Water, Environment and Health recently expressed concerns over the issue of dam sedimentation, as outlined in their report. The report indicates that approximately 50,000 large dams worldwide will experience a significant loss in their water storage capacity by 2050 due to trapping of sediment. Currently, these water reservoirs have already witnessed a loss of around 13-19% capacity due to sedimentation. Countries like the United Kingdom, Panama, Ireland, Japan, and Seychelles are expected to undergo the highest water storage losses by 2050, ranging from 35-50% of their original capacities.
Understanding Sedimentation and Dredging
Sedimentation is a process where sediments such as sand, gravel, and silt accumulate at the bottom of a dam-created reservoir. Over time, this build-up reduces the overall storage capacity of the reservoir, necessitating the removal of the sediment through a process called dredging.
Dredging involves removing accumulated sediment from the bottom of a reservoir. Employing various methods like mechanical dredging with a dredge machine or hydraulic dredging with a high-pressure water jet, the sediment extracted during this process is usually disposed of in a designated area away from the dam.
Causes of Sedimentation
Many factors contribute to sedimentation, including erosion upstream of the dam, runoff from urban and agricultural areas, natural processes such as weathering and erosion, climate change, deforestation, and poor dam maintenance. Each can lead to an increase in sediment runoff into the reservoir, which can cause sedimentation and reduce the dam’s effectiveness.
Impact of Dam Sedimentation
Sedimentation in dams has several ramifications, both environmental and economic. Environmentally, it reduces the water storage capacity, leading to potential water shortages and loss of aquatic habitats. Economically, it increases the costs of maintenance and dredging, reduces hydroelectric power generation, affects agriculture and industry water supplies, and can limit revenue from recreational activities. Dam sedimentation also leads to structural damage, affecting the dam’s foundation, turbine intake and efficiency, and even causing potential dam failure.
Addressing Dam Sedimentation
Addressing the issue requires various approaches like regular inspections and monitoring of dams for signs of weakness, erosion, and other potential issues. Emergency action plans are necessary to respond to incidences such as dam failure or excessive flooding. Additionally, environmental impact assessments must evaluate the potential impacts of a dam on the surrounding environment, including wildlife, aquatic species, and downstream communities. Furthermore, public consultation and participation in decision-making processes is crucial for any proposed dam construction.
Sample Examination Questions
An example question for UPSC Civil Services examination based on this topic could be: “Suppose the Government of India is thinking of constructing a dam in a mountain valley bound by forests and inhabited by ethnic communities. What rational policy should resort to in dealing with unforeseen contingencies?” (2018)
This article helps provide a deeper understanding of the problems associated with dam sedimentation and potential measures to address them. It is crucial for global efforts towards efficient water resource management and combating the impacts of climate change.