Hydrodams in Malaysia

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4.3 Environmental Implication of Dams

Dams have benefits us all; nevertheless, the implication especially to the environment is beyond good. The environmental impacts of dams are various. It includes direct impacts to the biological, chemical and physical properties of rivers. The construction of dams (which obstruct the river) destroyed the existing ecosystem balance. Besides changing the flow of the river, the wall of the dam also interrupt fish migration and other rivers’ population. Most dams were constructed without considering building a proper bypass system for these animals thus affecting their reproduction and life-cycle eventually leading to extinction. Dams also trap sediments which cause loss of sediment at downstream (also known as delta starvation). The sediment is essential for downstream ecosystem. When a river is deprived of its sediment load, in order to make up for the sediments, it seeks to recapture it by eroding the downstream river bed and banks leading to soil erosion.

Another significant impact is the transformation upstream of the dam from a free-flowing river to an artificial slack-water reservoir habitat. Changes in water circulation, temperature, chemical composition, dissolved oxygen levels and the physical properties of a reservoir are often not suitable to the aquatic plants and animals. In aggregate, dammed rivers have also impacted processes in the broader biosphere. Most reservoirs, especially those in the tropics, are significant contributors to greenhouse gas emissions (a recent study pegged global greenhouse gas emissions from reservoirs on par with that of the aviation industry, about 4% of human-caused GHG emissions). Besides that, dam also favours the spread of disease for example, dam reservoirs in tropical areas, due to their slow-movement, is literally breeding grounds for mosquitoes that could cause malaria. In general, large dams have led to the extinction of many fish and other aquatic species, the disappearance of birds in floodplains, huge losses of forest, wetland and farmland, erosion of coastal deltas, and many other immitigable impacts (Degeorges & Reilly, 2006).

4.4 Risks during Dam Construction

When we discuss the issue of safety especially in large construction (e.g. dams), the most concerning issue would be the design and stability of the structure. It is important to note that proper design of a structure is critical to prevent total or partial collapse of the structures, and thus to prevent damage to future users and residents in the area adjacent to the work being constructed (Aiken & Leigh, 2015). During construction of dams, other significant risks are slope stability issues and flooding. Dams constructed based on the maximum quantity of water in the river alone could lead to other devastating impact for example flooding especially during heavy rain where there is excessive water in the river. Appropriate standards and construction requirements are required to ensure that the downstream population at risk and the contractor are working within an acceptable risk.

Besides that, the safety of the personnel working on-site also needs full attention because it often considered as minor importance and usually neglected (Kansas Department of Agriculture, 2013). Health and safety of construction workers on site is a very important problem because the effects of accidents on job sites are very serious. Accident on site does not only cause material damage to machineries and equipment and but injuries suffered by workers may lead to disability and even death.

- Control Measures

It is estimated that, there are about 5,000 large dams of at least 50 years old. Over time, dams required major maintenance and the cost are increasingly more expensive. Without proper inspection and maintenance, older dams are at risk of bursts. With the current climate change; irregular hydrological patterns which have resulted in heavy storms and extreme floods could deteriorate dam safety. There is also a growing concern that dams can trigger earthquakes due to the weight of the reservoir coupled with other factors. Earthquakes could cause dam failure and dam burst leading to a more devastating impact not only to the environment but to people living in downstream area.

Nevertheless, dam failure could be prevented through a detailed inspection and monitoring (Barker, 2011). Elements that are critical for dam safety should be regularly examined (e.g. piezometric pressure, water level, seepage and alarm system) during its life time. In addition, the owner or operator of the dam should establish a safe operating procedure to ensure that the dam operates under safe conditions. Failure or misoperation can result in the release of the reservoir contents (e.g. water, mine wastes or agricultural refuse) which can cause negative impacts upstream or downstream or at locations remote from the dam.

- CONCLUSION

Since the 18th century until recent, dams built to store water have occasionally failed with the resulting loss of life, social, economic financial and environmental losses. Failures have occurred when dams were built without the application of proper engineering principles.

However, there are dams built within the acceptable engineering standards of design and construction principles. With the increased of knowledge among engineers on dam safety, safe dams can be built and existing dams can be securely maintained (United Nations Economic Commission for Europe, 2006). Moreover, the owner must aware that the dam should comply with current engineering standards for its safety and the dam must be assured to operate in a safe manner. An emergency preparedness procedure is essential so that the owner or operator of the dam is prepared for an emergency situation at the dam. With all these, the risk of dam failure can be minimised.

REFERENCES

Aiken, S. R. & Leigh, C. H. (2015): Dams and indigenous peoples in Malaysia: Development, displacement and resettlement, Geografiska Annaler: Series B, Human Geography 97 (1):69–93.

Ansar, A., Flyvbjerg, B., Budzier, A., & Lunn, D. (2014). Should we build more large dams? The actual costs of hydropower megaproject development.Energy Policy, 69, 43-56.

Bagher, A. M., Vahid, M., Mohsen, M., & Parvin, D. (2015). Hydroelectric Energy Advantages and Disadvantages. American Journal of Energy Science,2(2), 17-20.

Barker, M. (2011). Australian risk approach for assessment of dams. In 21st Century Dam Design–Advances and Adaptations, Proceedings of the 31st Annual USSD Conference,