Commentary: Dam collapse threatens Central Asia

TASHKENT, Uzbekistan, Nov. 18 (UPI) -- A lake in the Pamir Mountains of Tajikistan threatens several million people in Central Asia because a powerful earthquake could send its waters flooding vast areas, reaching as far as the shrunken Aral Sea, experts from the former Soviet Union said.

Lake Sarez was created as a result of an earthquake in 1911 when an enormous landslide blocked the Murgab River. The Usoi natural dam formed a lake 37 miles long and 550 yards deep, located at an altitude of about 2 miles.

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The volume of water in the lake has increased since its formation -- based on different estimates -- to between 20.15 billion and 24.7 billion cubic yards. The dam is more than 600 yards high.

"Nineteen-million metric tons of water affect the dam, trying to move it," Akram Irgashev, Uzbekistan's former deputy minister of energy, told United Press International. "Just the force of friction keeps the dam from moving."

"But the dam is natural," he continued. "It is not man-made. Water seeps through it, which will result in bringing the force of friction to naught."

The hydraulic pressure is creating conditions that are lifting the dam a little, he added. "After years of a lull, the Usoi (dam) has started to 'breathe,' stir and grow, displaying an evident tendency to slip down and fall," he said, citing reports from the Sarez agency operating in Tajikistan.

The main threat is from the right bank, a partially collapsed body of earth and rock, with a mass of up to 2.6-billion cubic yards that could fall into Lake Sarez and generate an enormous wave, Irgashev said.

Tajik experts reportedly said the wave would be 110 to 165 yards in height could overtop the dam and wash it away.

Specialists often compare the possible catastrophe in Central Asia to one that occurred in northern Italy in 1963 when a huge landslide fell from Toc Mountain into an enormous basin sustained by the Vajont dam. A giant and violent wave, created as a result of the movement, completely destroyed the villages of Erto, Casso and Longarone, killing 2,500 people.

The volume of water in Sarez is 100 times greater than in the Vajont basin, according to Leonid Papyrin, a Russian scientist who has worked in Tajikistan. He wrote an article about the potential danger titled, "The Sarez catastrophe: A geophysical forecast."

Papyrin said the volume of a possible landslide at Sarez would be several times larger than the fall from Toc Mountain, and the power of the landslide would be greater because the lake's elevation is higher.

"Accordingly, consequences of the catastrophe at Sarez could be several hundred times as destructive as ... (in Italy)," he added.

The event could involve Tajikistan, Uzbekistan, Afghanistan and Turkmenistan. It could cause extensive damage and destroy frontier posts between Tajikistan and Afghanistan and between Uzbekistan and Afghanistan, Papyrin said.

The Sarez waters could reach the Aral Sea through the Murgab, Bartang, Panj and Amu-Darya rivers.

"The catastrophe could be caused by not only an earthquake but also a subversive act," he added.

During the civil war of the 1990s, military commanders in the United Tajik Opposition reportedly threatened to blow up the Usoi dam.

Granik Kornakov, the former director of the Sredazgidroproekt institute, told UPI that an earthquake exceeding 5 on the Mercalli scale would collapse the lake's right bank. The Mercalli scale, which runs from 1 to 12, gauges intensity at a specific location.

The area experiences considerable seismic activity. Temblors that could cause the right bank collapse recur every 100 years and the latest one in 1911 created the lake, Kornakov said.

Having studied Sarez and its right bank, in the early 1980s Sredazgidroproekt offered two ways of fixing the problem: Constructing tunnels for water withdrawal or raising the top of the dam by 55 yards.

One challenge has resulted from the collapse of the Soviet Union, Kornakov said. Now, it would be impossible to undertake such a project because of the high cost, he explained. "The most sensible thing is to put observation and warning systems in order," he said.

The World Bank has begun a Lake Sarez mitigation project to help "alert and prepare vulnerable people in case of a disaster associated with an outburst flood from Lake Sarez and other frequent natural hazards," the bank said in a statement. The project includes design and installation "of a monitoring system and an early warning system to safeguard the life of the communities located in the Murgab and Bartang valleys."

Some western experts have downplayed the risk of a dam collapse. For example, in 1999, a risk assessment mission to the lake, sponsored by the United Nations International Decade for Natural Disaster Reduction Secretariat, said a complete or even partial collapse of the Usoi dam is very unlikely. However, "the threat of collapse of the right bank, although smaller than previously believed, remains an unfortunate reality," the mission wrote in a report.

"Even a medium sized surge wave overtopping the dam could affect the entire population of 7,800 people living in the Bartang valley and could possibly extend beyond the city of Rushan and affect the first three major towns along the Panj river where an additional 25,000 people live," the report continued.

Dr. Donald Alford, of the University of Colorado in Boulder, who was team leader for the mission, told UPI some of the warnings could be due to various agendas represented by special interest groups, both within and outside Central Asia.

"In many ways, political or journalistic considerations sometimes take precedence over the findings of the technical and engineering studies of the lake, dam, and downstream valleys," Alford said.

Marina Kozlova covers science and environment issues in Central Asia for UPI Science News. E-mail sciencemail@upi.com