Sarez Lake is a mountain lake deep in the inaccessible Pamir Mountains of Central Tajikistan. The lake was created in 1911, when an earthquake, estimated at 7.0 at the Richter Scale, and a following landslide of 2.2 million cubic meters, created a huge natural barrier known as the Usoi Dam. At a height of 567 meters, it is the largest dam in the world, either natural or man-made.

Thanks to its extremely remote location, it took more than a month before local authorities became aware of the creation of this huge dam, which successively allowed the valley to be flooded by constant rain and meltwater. It wasn’t long before the entire unpopulated valley was flooded, and created a lake with a volume of more than 16 cubic kilometers.

But this lake is a constant source of worries to the Tajik government, since, given its location in one of the most earthquake-prone regions in the world, it seems highly likely that a future earthquake could destroy the dam and release a catastrophic flash flood. If this flood occurred, the entire content of the lake would be pressed through the narrow valleys of Tajikistan, destroying everything in its way, endangering more than five million people. It could also affect the neighboring countries Afghanistan, Uzbekistan and Turkmenistan.

Another constant threat is that filtration water apparently created a number of cavities inside the dam, which might destabilize the entire dam wall. But the largest threat is a partially detached rock mass of three cubic kilometers at the edge of the lake, which, if it fell into the lake, it could put too much additional pressure on the dam, and might result in its collapse.

In 2004, a monitoring system has been put in place on Sarez Lake and valleys, that would be affected by the destruction of Sarez Lake, received an early-warning system.