Abstract
Abstract. The Poiqu River basin is an area of concentration for glaciers and glacial lakes in the central Himalayas, where 147 glacial lakes were identified, based on perennial remote sensing images, with lake area ranging from 0.0002 to 5.5 km2 – a total of 19.89 km2. Since 2004, the retreat rate of glacier has reached as high as 5.0 km2 a−1, while the growth rate of glacial lake has reached 0.24 km2 a−1. We take five typical lakes as our case study and find that the retreat of glacier area reaches 31.2 %, while the glacial lake area has expanded by 166 %. Moreover, we reconstruct the topography of the lake basin to calculate the water capacity and propose a water balance equation (WBE) to explore the lake evolution. By applying the WBE to the five lakes, we calculate the water supplies of the last few years and compare this with the results of field surveys, which are in agreement, within an error of only 1.86 % on average. The WBE also reveals that the water supplies to the lake depend strongly on the altitude. Lakes at low altitudes are supplied by glacier melting, and lakes at high altitudes are supplied by snowmelts. The WBE is not only applicable for predicting future changes in glacial lakes under climate warming conditions but is also useful for assessing water resources from rivers in the central Himalayas.
Highlights
Worldwide glacial retreat due to global warming has led to great changes in alpine glacial lakes (IPCC, 2013; Mergili et al, 2013; Nie et al, 2014; Wang and Zhang, 2014; Prakash and Nagarajan, 2017)
In the central Himalayas, temperature increased at a rate of 0.3–0.4 ◦C per decade, nearly 2 times the global rate; and at present, the glacial lake area increases by 40 % at a rate of 0.28 km2 a−1, which is higher than the other regions in the Himalayas (Nie et al, 2017)
The Poiqu River basin is located in the central Himalayan terrane (Zhang et al, 2015), which was formed by the Indian–Eurasian plate collision (Zheng et al, 2014)
Summary
Worldwide glacial retreat due to global warming has led to great changes in alpine glacial lakes (IPCC, 2013; Mergili et al, 2013; Nie et al, 2014; Wang and Zhang, 2014; Prakash and Nagarajan, 2017). In the central Chinese Himalayas, the glacial lake area has increased greatly, from 166.48 to 215.28 km, the number of lakes has decreased from 1750 to 1680 in the last 40 years (Wang et al, 2012). Su et al.: Changes in glacial lakes in the Poiqu River basin in the central Himalayas et al, 2015) This expansion depends on the fact that most lakes are fed by the meltwater of glaciers. Landsat data indicate that the annual retreat rate of glaciers in Poiqu basin was approximately 0.54 % in 1976–2010, and the area of glacier lakes increased up to 1.3 % per year in 1986–2001 (Chen et al, 2007). We use multisource images from the last 30 years to explore the lake variation in the Poiqu River basin and provide a quantitative analysis of the water balance, which leads to a method for assessing glacial lake change under a warming climate and sheds new light on the mechanism of glacial lake evolution
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