Forest | Flooding | Physical Changes | Lost of Species | Climate | Disease
Construction | Water Diversion | Alternatives

With any development project, environmental impacts are crucial factors to consider before taking any major steps towards action. This is especially true with projects concerning large hydropower development projects, as they can have many adverse affects on the surrounding and wider environments.

The impacts often lead to a chain of events affecting people, plant and animal species, whole ecosystems, economies, and the livelihoods of thousands. The relationship between all living organisms and their systems is a delicate balance. When it is disrupted it can cause havoc, leading to serious and sometimes permanent damage.

An un-dammed river is dynamic, always changing and comprised of many different ecological niches (specific place or role an organism has in its ecosystem). Ecosystems and cultures are dependent on this dynamism. Developments on the Salween River, including hydropower and water diversion projects will destroy the delicate balance between the river and its watershed, a relationship, which may have taken many thousands of years to evolve. The majority of the effects of a dam built on the Salween River will occur in downstream communities and ecosystems of Burma, but Thailand's forests, River, and people will also be affected.

Dams decrease the flow of River, which means fewer habitats, nutrients, and increased stresses on aquatic life downstream. They can cause massive changes in the ecology and water quality of the river and its tributaries. Flooding from the dam will permanently submerge forests and fertile land along the river and in the tributary valleys. Areas that are used for seasonal cultivation of crops, as well as areas that are supposed to be protected as wildlife sanctuaries will be underwater. The western edge of the Salween Wildlife Sanctuary in Thailand could be affected if the projects are implemented. Likewise, important archaeological and cultural sites will be lost. In addition, dams have huge impacts on coastal ecosystems, due to the changing in timing and volume of flows of water and nutrients from the River into estuaries and oceans.

Listed below in some detail, are some of the potential environmental impacts that hydropower development projects on the Salween River can lead to.

Forest

Vast areas of forest will be logged or flooded during the construction of the dam. Access roads will have to be built, which will open up more areas of forest to loggers, hunters, settlers, and the military.

As people are forced to relocate, more land will be cleared in new areas for the planting of crops by the displaced.The resulting deforestation can cause many problems. It destroys and reduces habitat for many species, thereby putting them at risk of being killed off. It increases the chance of flooding during the rainy season. It intensifies drought in the dry season. There is also an increase in erosion and loss of valuable topsoil. Furthermore, for the people who depend on the forest as a primary source of food, medicine, building materials, etc., their food security and livelihoods are jeopardised.

Flooding

Damming River disrupts crucial natural flood cycles. This can lead to widespread damage to ecosystems affecting flora, fauna, the regional economy, and food production of the people who depend on the river and its flood cycles. Seasonal flooding is essential for re-fertilising banks and surrounding flood plains. A dam will decrease the water flow and change the rate, duration, and timing of flooding.

Forests play a critical role in the regulation of flooding by absorbing high floodwaters during the rainy season and slowly releasing the stored water in the dry season. With extensive deforestation there is an increased severity of flooding as the water washes into the river, taking with it valuable topsoil. Furthermore, dams, when overfull, may release much larger than natural amounts of water in very short periods, sometimes causing more damaging flooding than previously known in the river basin.

Physical changes

For several hundred kilometres, the free flowing river would be changed into a deep, slow/still moving water system. This major change influences the physical and chemical characteristics of the water: the pH balance (acidity), clarity, oxygen levels, and temperature.

Decaying organic matter can create what are known as eutrophic conditions in the reservoir, leading to algae blooms, further oxygen depletion, and massive fish kills. When this happens, the water from dam reservoirs and directly downstream is often unfit for human and animal consumption for years after the project is completed.

The proposed dam sites along the Thai-Burma border are situated along a major fault line. Reservoirs increase the risk of earthquakes by adding immense pressure to the earth from the large volumes and weight of the stored water.

Dams upset the geological processes of erosion and deposition. Southeast Asia is part of the "green belt" of tropical rainforest, which runs along the equator. Rainforest soils are often extremely delicate; their thin layer of topsoil highly vulnerable to erosion. Eroded soils are washed into the dam reservoirs, causing a build-up of siltation that eventually leads to loss of the reservoirs' storage capacity over time. The soil deposits that are trapped behind the dam's barriers deprive the riverbanks downstream of seasonal nutrient replenishment. Loss of the source of silt and soil from upstream also causes serious erosion of the riverbank land. The especially fertile delta areas stop growing, start disappearing, and loose their source of fertility. This loss of annual nutrient deposits and water-based oxygen reserves can affect and disrupt the productivity of the downstream forests, miles away from the dam site. There will be an increased dependency on chemical use for agriculture with the loss of natural re-fertilisation processes from flooding on the banks and in the basin.

Reduced water flow in the delta area will cause salt water to intrude up the river and underground, which will damage crops, soil and water supplies in Moulmein and all around the estuary and is likely to cause die-back of the extensive mangrove forests there.

Loss of species

Hydropower development can have serious effect on the survival of some species that live and depend on the areas in the river basin. All systems are delicately balanced and interrelated. Therefore, disrupted food chains and other systems will face serious impacts, affecting both species living on and offshore.

Biodiversity is lost with the building of dams. Habitats are drastically reduced with the clearing of forest, endangering many species. Vast areas are flooded, drowning and displacing many animals. Reservoirs created by the dams also can block cross-river animal migrations.

With the building of a dam, aquatic habitats will be destroyed. Fish will not be able to reach spawning and feeding grounds, as the dam will block them from carrying out seasonal fish migrations. The natural flow of the river will be altered, causing changes in the chemical and physical characteristics of the water that contribute to degradation of the fish habitats.

About one third of the fish species living in the Salween River are endemic, and exist only in this river. The survival of these species is greatly jeopardised with the building of a dam. The native fish species in the Salween River have adapted to live in a riverine system, and their environment would be abruptly changed into a reservoir, leading to potentially serious problems. It is probable they will not be capable of adapting quickly enough to the changing environment. This will lead to a loss of important native species.

Climate

Dams also contribute to global warming. Trapping of nutrients behind the dam decreases fertilisation of oceanic plankton, which play a major role in taking carbon dioxide out of the atmosphere, hence affecting and contributing to the serious issue of global warming. Methane released from anaerobic decomposing of flooded plants also releases significant amounts of a major greenhouse gas. Accumulation of water in large reservoirs may also have affect on the local climate.

Disease

There is an increased risk for disease with the formation of stagnant pools. Diseases, especially malaria and schistosomiasis would thrive, as the still waters are prime breeding grounds for malarial mosquitoes and the worms, which carry schistosomiasis.

Construction

During the construction of the dam, tonnes of explosives will be used. Large-scale extractions of building materials from surrounding areas such as gravel, sand and clay will be used. Thousands of workers are needed during the dam construction. They will rely heavily on the forests in the area for daily firewood and food, and will also cause an increased concentration of wastewater and sewage that will be dumped into the river.

Water Diversion

With water diversion projects, the decreased water flow in the river will change the ecology and water quality. It could also impact small-scale irrigation systems of agricultural communities, restrict cultivation of crops, and disrupt seasonal fish migrations. The diversions will interrupt the natural seasonal flows, and thereby disrupt the nutrient supply cycles and habitats. Water diversion projects and decreased flow volume to downstream areas can lead to increased saltwater intrusions into the Salween delta. This will have effects on drinking water, could destroy paddy fields, and will alter the aquatic balance for communities and their ecosystems. Salinisation of the lowland paddy fields, and decreased fish populations will thereby affect the food production capacity and livelihood security of the people who depend on the Salween delta's resources.

Alternatives

It is important for countries to explore alternative sources of energy that are more environmentally friendly. Ethanol-based petroleum made from sugarcane, natural gas, solar and wind energy, agricultural waste (palm, rice husks, and pig manure), and micro-hydropower plants are all examples of alternative methods for obtaining energy. Countries need to also encourage and practice energy conservation. In-depth studies (Environment Impact Assessments) are critical to evaluate and quantify potential project impacts. It is very important who conducts the EIA's, as in many cases, the engineering companies involved in the dam building also do the assessments, which could affect the results of the studies.

Sources

• Cummings, B. 1990. "Dam the River, Damn the People". Earthscan Publications Ltd, London.
• Kamkongsak, L. and Law, M. March-June 2001. "Laying Waste to the Land: Thailand's Khong-Chi-Mun Irrigation Project". Watershed 6(3): 25-36.
• Miller, F. November 1999- February 2000. "Environmental Threats to the Mekong Delta". Watershed 5(2): 38-42
• Office of the National Economic and Social Development Board Water Resources Engineering Program. 1994. "Study of the Potential Development of Water Resources in the Salawin River Basin". Bangkok, Thailand.
• Towards Ecological Recovery and Regional Alliance. July 1997. " Hydroelectric and Transbasin Water Diversion Projects in the Salween River Basin". Bangkok, Thailand.
• Water and Mineral Resources Section, Environment and Natural Resources Development Division, UN Economic and Social Commission for Asia and the Pacific. September 1999. "Workshop on Transboundary Waters: The Salween Basin". Chiang Mai, Thailand.
• Watershed Report. November 1999-February 2000. "A Dam for Burma's Generals." Watershed 6(3): 43-44.
• Wong, S. 1999. "The Impacts of Large Dams and the International Anti-Dam Movement." International River Network, United States.