THE FEATURES OF A GLACIAL LAKE OUTBURST MODELING: A CASE STUDY OF VARSHEZKUL LOWER (TAJIKISTAN)

Abstract

The study deals with the modeling of a possible outburst flood with the example of glacial lake Varshezkul Lower located in the Western Pamirs. From the formation of the lake in 1968 and until 2022, the lake increased by 8.3 times, its active growth was observed until 2000. According to the survey of the valley in 2018, the volume of the lake was 1.94 million m3. To estimate the maximum flood discharge, the FLOVI program was used, which includes model equations of a lake outburst through an intraglacial tunnel developed by Yu.B. Vinogradov. The simulation showed the initial water temperature in the lake to be the most sensitive parameter of the model. The maximum discharge of an outburst flood at a water temperature of 4 °C will be 2.8 times higher than for 0 °C and will amount to 400 m3/s. In the range from 0 to 4 °C, the outburst flood discharge will increase by approximately 30% 1°C. The results of processing the ERA5 reanalysis (ECMWF Re-Analysis 5) were presented in the form of graphs of the surface layer temperature, bottom and general temperature in the period from June to October for 2018-2022. An almost complete coincidence of values was observed, and the temperature on the dates of the freeze-up on the lake was significantly overestimated. This may be due to a low resolution of the data (30 km) and a small area of the lake. Also, the simulation results were compared with estimates of the maximum outburst flood discharge from empirical dependences. The difference in the flow discharges determined by various formulas was about 95%.