In-situ water quality investigation of the lakes on the Tibetan Plateau

The lakes on the Tibetan Plateau (TP) account for 57% of the total lake area in China [1], which is a key component of the Asia water tower [2-4]. A recent study showed that there are 1424 lakes greater than 1 km² on the TP, while the total lake area reached 5.0 × 10⁴ ± 791.4 km² in 2018 [5]. Most lakes on the TP are closed and are less disturbed by human activities than the other inland water bodies in China. Therefore, the lake water's hydrochemical characteristics, through the influence of water profile thermal distribution, energy exchange with surface air moisture, and lake ecological conditions, are sensitive to climatic and environmental changes in the area [6]. However, only a few main lake water parameters were achieved during the first Integrated Scientific Expedition on the TP before the 1980s [7]. Even in the past few decades, there have been only a few published works on investigations on the water quality of the large lakes on the TP, such as Nam Co [8], Tangra Yumco [9], Yamzhuo Yumco [10], Mapam Yumco [11], and small valley lakes such as Ranwu Lake [12]. This study, based on the hard investigation work, provides the in-situ lake water parameters of 124 closed lakes with a total lake area of 24,570 km², occupying 53% of the total lake area of the TP (Fig. S1 and Table S1 online), and we have presented the primary result of their numerical and spatial distribution and related factor analyses.