Assessment and inventory of hazardous mountain lakes in Kyrgyz Republic

More than 90 % of territory of Kyrgyz Republic are mountains.  More than two thousand lakes have formed but only some lakes pose a threat to lives, assets and livelihoods. Many of these lakes are seasonally dynamic, and form in ice-rich permafrost environments that are characteristic of the region. The objective of this study was to describe and implement an evidence-based expert lake hazard assessment criteria, to produce an updated inventory of hazardous lakes, which are susceptible to outburst within the territory of Kyrgyz Republic. A total of 368 lakes susceptible to outburst in Kyrgyzstan were inventoried and classified into 5 classes: ice-dammed, ice-cored moraine-dammed, ice-free moraine dammed, bedrock-dammed and moraine- dammed, and landslide-dammed lakes. The hazardous lake inventory was most recently updated in 2021 based on field works and remote sensing analysis.

All 368 lakes were described by a number of quantitative and qualitative characteristics and were assigned different levels of outburst susceptibility. All studied lakes are situated within the elevational zone between 1200 m.a.s.l. and 4300 m.a.s.l. All lakes were estimated in terms of their surface area from remote sensing data for different years, which ranges from thousands to millions of square meters. For 47 ice cored moraine dammed lakes bathymetry measurements were conducted, for many of them several times.

The outburst susceptibility was estimated according to 4 hazard categories and each lake is assigned within a certain category depending on current lake characteristics. A particular feature of the non-stationary lakes found in this region is the rapid changes in outburst susceptibility that can occur over short time-periods. A total of 111 lakes, which at least once have been assigned with the highest hazard levels (the 1^st or 2^nd category) in the period from 2006-2017 were analyzed for their changes over time. According to the analysis, the hazard level of many lakes varies over time and the number of category 1 and 2 lakes has considerably decreased in the recent decade. Lakes of the 1^st and 2^nd hazard categories decreased since 2006 by 57 % and 45 % respectively (from 21 to 9 and 49 to 27), while the number of lakes of the 3^rd and 4^th categories increased from 35 to 58 and 1 to 16.

The lake hazard assessment scheme developed for the Kyrgyz Republic may be a valuable tool for scientists and authorities dealing with outburst flood hazards in other similar environments of Central Asia and elsewhere.