Popular Science: What is the fate of proglacial lakes?
Glacial meltwater is one of the important water sources. In some parts of the world, including central Asia, glacial meltwater contributes up to 40–70% of the total amount of summer runoff. Glacier mass balance and glacier cover influence the hydrological regimes of rivers, which affects not only the water supply of the local population, but also the entire ecosystem in the basin. For this reason, it is very important to study this rapidly changing phenomenon .
Experts in hydrology and hydrogeology therefore set out for the Kyrgyz part of the Tian Shan Mountains to examine the hydrological regime of the dynamically changing Adygine glacial-moraine area, which belongs to the Ala Archa watershed. This proglacial area includes many moraines and several lakes.
Monitoring in the area started in 2007 when the first pressure sensor for lake water level monitoring was installed in one of the lakes and then in two other lakes five years later. In addition to these data, many other modern methods have been applied for detailed research. It was important to find out the glacier meltwater drainage direction and possibly its retention in the system. Due to the complex terrain, standard methods could not be used, so the researchers opted for a fluorescent tracer. It is a dye that absorbs light of a certain wavelength and reflects light of a longer wavelength. In addition to being very slightly reactive, its advantage is also in the high detection rate even at very low concentrations. The analysis of hydrogen and oxygen isotopes (δ2H and δ18O) in lake waters was also used to determine possible differences in the water supply of thermokarst lakes.
Source: Authors of the original article, modified.
Despite the same water source of the lakes, analyses of mean daily water-level fluctuation amplitude showed a significant effect of the lakes’ distance from the glacier, at the same time showing the effect of interconnection between the individual lakes at higher flow rates. In addition to the different altitudes and position of the lakes, the extent of impermeable layers forming the basin and the distribution of the drainage channels played the most important role.
During the year, it was possible to observe a considerable fluctuation in the lake water level, the highest in August and the lowest during the winter. It was found that the glacial meltwater flows through the lakes and further downstream through a rock glacier relatively fast (0.085 m.s−1), with only a small percentage of the meltwater (only 0.03%) contributing to the direct runoff.
Along with climate change and the melting of glaciers, the hydrological regime of rivers and the amount of water supplying these watersheds are also changing rapidly. The results of the study show that surface and subsurface runoff systems are very dynamic and depend on many factors. Therefore, it is possible to expect growing importance of studying the proglacial environment.
Kateřina Fraindová
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