Location and Origin
The lake is located in the Murghab District of the Gorno-Badakhshan Autonomous Region in Tajikistan. In Russian, it is more correct to call it "Sarezskoye Ozero" (Sarez Lake), but today the direct translation from the Tajik "Kuli Sarez" is more commonly used.
It was formed as a result of a colossal natural disaster. On February 18, 1911, a powerful earthquake triggered a massive landslide that completely blocked the channel of the Murghab River. This natural dam, named the Usoi Landslide, marked the beginning of the lake's history. Accumulating water gradually flooded the village of Sarez, from which the lake takes its name. Active filling continued until 1926, and the lake reached its present level only by the mid-1940s.
Lake Characteristics
Sarez is one of the largest high-mountain lakes in the world. It lies at an altitude of about 3,250 meters, stretches 70 km in length, and reaches a depth of 505 meters. Its water volume is colossal—over 17 cubic kilometers.
The lake's water is ultra-fresh, crystal clear, and rich in oxygen. It is home to several fish species: the marinka, false osmans, and Tibetan loaches. Through the Usoi Landslide, the lake is hydrologically connected to a smaller neighbor—Lake Shadau, which is fed by the Shadau and Marjanay rivers.
The Usoi Landslide: Scale of Tragedy and Threats
The Usoi Landslide, which created the lake, is the world's largest landslide dam complex. It buried the village of Usoy and all its inhabitants. Only three people miraculously survived, as they were visiting relatives in nearby Sarez at the time. The volume of the landslide is estimated at 2.5 cubic kilometers, with a mass of over 6 billion tons.
The main danger lies in the potential breach of this natural dam. In such an event, a gigantic debris flow would race down the valleys of the Bartang, Panj, and Amu Darya rivers, threatening the lives of nearly 6 million people across several countries. These concerns are not unfounded: geologists have determined that in the past, at least nine similar lakes have existed and subsequently vanished due to breaches in this very valley.
The Right Bank Landslide and the Search for Solutions
The threat comes not only from the erosion of the landslide dam itself. In the 1960s, scientists discovered a movable body of shale on the lake's right bank—the so-called "Right Bank Landslide." Its collapse into the lake could cause water to overtop the dam, potentially leading to its destruction.
Technical solutions to mitigate the risk (lowering the lake level, constructing catchment dams downstream) were proposed back in Soviet times. However, after the USSR's collapse, the large-scale project became too much for one country to handle. Today, with support from the World Bank, a risk reduction program is being implemented. So far, its main results have been an early warning system, an emergency response protocol, and the creation of "safe havens" stocked with provisions and medicine.
An Optimistic Viewpoint
It is worth noting that not all experts are pessimistic. Some scientists believe the Usoi Landslide is a stable formation capable of standing for millennia. As evidence, they point to the powerful Pamir earthquake in 2017, which, according to monitoring data, caused no damage to the dam. Officials from Tajikistan's Committee for Emergency Situations, which conducts constant monitoring of the lake, also express optimism. "Sleep soundly. No significant changes have been observed at Sarez."
