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.