2. STUDY AREA
Gonghe Basin (35.45°–36.93° N, 98.77°–101.37° E) is located in the north-eastern Tibetan Plateau (Fig. 1a) at a mean elevation of approximately 3,000 m. This region is characterized by an alpine arid and semi-arid continental climate (Dong, Gao, & Jin, 1993). The basin has an elongated shape, which is surrounded by the Xiqing, Heka, Ela, Wahong, Waligong, and South Qinghai mountains (Fig. 1a) (Dong et al., 1993).
{Figure 1}
Genggahai Lake (36.18° N, 100.1° E) is located in the central part of the Gonghe Basin (Fig. 1a). The present-day area of the lake is approximately 2.0 km2, with a surface elevation of 2,860 m, a maximum depth of 1.8 m, water salinity of 1 g L–1, and a pH of 9.2 ± 0.5 (Qiang et al., 2013). The lithology of the Genggahai Basin is dominated by limestone, sandstone, marble, slate, and schist (Dong et al., 1993). Groundwater is the main water source in the Genggahai Lake (Qiang et al., 2013). Qiang et al. (2017) suggested that there is a close hydraulic link between the Shazhuyu River and Genggahai Lake. The lake is inhabited by a large number of submerged macrophytes, such as Chara spp.,Myriophyllum spicatum L. , and Potamogeton pectinatus L. (Fig. 1b), as well as gastropod molluscs (Qiang et al., 2013). The entire lake is surrounded by grassland, particularly the desert grassland ecosystem dominant in the Genggahai Basin. This region is characterized by strong wind-blown sand movement. Human activity in this region remains limited, with only a small number of Tibetan herdsmen, who graze their livestock on the grasslands surrounding the lake.