Satellite monitoring of the Sardoba Reservoir in Syr Darya River basin (Uzbekistan) before and after a dam collapses on May 1, 2020

Abstract

The Sardoba Reservoir, operating since 2017, is located in the basin of the transboundary Syr Darya River in Uzbekistan near the Kazakhstan border (20 km). The Reservoir is located in the center of the Golodnaya Steppe. Its bed is a flat territory with an area about 60 km2 surrounded with dams. On May 1, 2020, a side dam collapsed resulting in catastrophic flooding of the downstream lands in Uzbekistan and Kazakhstan. The 115 images of Sentinel-2A and SRTM-2000 DEM were used to restore the dynamics of water masses in the Sardoba Reservoir during the last 4 seasons (2017-2020). The Reservoir operated in irrigation mode. The water accumulated during the cold period was used in May-September. The Reservoir was never completely filled. The maximum of water deposit in the Reservoir of 515 million m3, estimated from satellite data, was registered on April 24, 2020, on the last satellite visit before the accident (6 days). As a result of the dam collapse, about 400 million m3 of water from the reservoir was lost, and its water level fell by 18 m. According to Sentinel-2A image of May 4, traces of flooding are registered on an area of approximately 600 km2. The lowland near the border between Kazakhstan and Uzbekistan was particularly affected, where a newly-formed water body with an area of about 200 km2 covered the arable land and several villages, mainly on the Kazakhstan territory.