Forests and water - case studies
Lake Sarez: the political and financial implications of a potential mountain catastrophe in Tajikistan
Lake Sarez is in the Pamir mountains of Tajikistan, at about 3 000 m above sea level. It was formed by a very large landslide, which was set off by an earthquake in the winter of 1911. The landslide was 2 to 3 km3 in volume and formed a dam of about 500 to 600 m high and 2 km wide across the Murgab river. The Murgab is a tributary of the Bartang river, which flows from the Murgab for 120 km through a massive mountain gorge to join the Pianj river, a tributary of the Amu Darya. The Amu Darya is one of the two major rivers that drain into the Aral Sea, 2 000 km below the dam.
The mass of rock and earth that formed Lake Sarez is called Usoi dam after the village that it completely annihilated. Initially, the level of the lake rose by about 75 m a year, and today it is more than 60 km long with a maximum depth of more than 500 m. Its total volume is about 17 km3, approximately two-thirds that of Lake Geneva.
The lake is in a region that has faced political and military tension for more than 200 years. Currently, there is actual or potential unrest in many of nearby countries: Afghanistan, Pakistan, Kashmir, India, the Islamic Republic of Iran, Iraq and Turkey.
The Pamir mountains are one of the world’s most active seismic regions, so Lake Sarez is a focal point for much concern. There are several ways in which a disaster of significant proportions could be triggered: a major earthquake could shatter the Usoi dam and send an enormous flood wave down the Bartang valley into the Pianj and Amu Darya rivers; as the lake continues to rise - by about 5 cm/year during the 1990s - the dam could overflow or collapse under the pressure of water; the water that is currently piped through the dam could expand and cause the dam to collapse; or another large landslide could fall into the lake, generating a giant wave that overtops the dam. Even if such a wave did not break the dam, the wall of water rushing down the Bartang valley could set off fast-moving mudflows and trigger secondary landslides. It has been estimated that the lives of up to 5 million people could be affected by such a disaster. Torrential floodwaters could extend as far downstream as the Aral Sea, with the additional danger of disturbing the toxic sediments that have been exposed as the sea has dried up.
Soviet and Tajik scientists became aware of the threat posed by Lake Sarez some decades ago. Early warning and monitoring of the lake level were established, but these ceased when the Soviet Union collapsed. Civil war between 1992 and 1997 meant that the problems of Lake Sarez were put aside.
In recent years, the regional government and international organizations have started to pay more attention to the dangers posed by Lake Sarez. Reconnaissance visits have been made to the lake, the dam and Bartang valley, and high-level planning meetings have been held. The Asian republics concerned, especially Tajikistan, believed that the worst-case scenario total collapse of the Usoi dam could occur, and a major investigation was conducted in June 1999, when an international group of engineers, geophysicists, geologists and geographers examined the situation at Lake Sarez. They agreed unanimously that the worst-case scenario was sufficiently unlikely to be accorded low priority, but they strongly supported the installation of monitoring, early warning and emergency preparedness systems.
The international team recommended that computer mapping and simulation of the potential impacts of various levels of natural disaster be undertaken, and that all the villages in Bartang valley should be involved in emergency preparedness. It also recommended that further, more detailed studies be undertaken of local people’s cultural and socio-economic situation. Sites for safe havens should be located and equipped, and local people’s attitudes about the various levels of possible danger should be taken fully into account. In February 2000, these recommendations were adopted, under the leadership of the World Bank and with contributions from major donors.
The case of Lake Sarez centres on the question of how to determine the likelihood of a potentially catastrophic natural event. Geophysical considerations should be at the core of this, but geopolitics and the attraction of international funds tend to play critical roles in decision-making. Although the independent team of scientists found unanimously that the worst-case scenario was unlikely, national and international agencies are undertaking expensive actions to monitor the lake, the dam and local seismic activities and to prepare for emergency evacuation. This is an instance where a potential upstream/downstream catastrophe, rather than its actual occurrence, is causing major social, economic and political repercussions. The decision to spend millions of dollars on monitoring and preparing for an emergency that seems unlikely to occur, rather than investing the same amount in sustainable development of the Tajik uplands, is controversial.
Adapted from J. Ives. 2001. Highland-lowland interactive systems.<p>Download the full-text document<br><br></p>