Exploring the geomorphological processes of Qinghai Lake and surrounding lakes in the northeastern Tibetan Plateau, using Multitemporal Landsat Imagery (1973-2015)

Studies of lake's coastline and shape changes and the influencing factors will contribute to knowledge about the geomorphological and hydrological evolutions of those lakes. This study extracted coastlines of Qinghai Lake and surrounding lakes in the northeastern Tibetan Plateau from multitemporal remote sensing data from 1973 to 2015. The geomorphological processes and the reasons for area and coastline variations were then analyzed. The results showed that: the changes of the total lake area were divided into three stages: the stable decrease stage (1973-1988), the fluctuant decrease stage (1988-2005), and the rapidly increase stage (2005-2015). The changes of Qinghai Lake area and Gahai Lake area showed a similar trend as the total lake area. The Erhai Lake area fluctuated from 1973 to 2004 and then increased from 2004 to 2015. Haiyanwan Lake was isolated from Qinghai Lake in 2003 and was linked into Qinghai Lake in 2006, again. The lakes area variations, excluding Erhai Lake and Shadao Lake, were positively correlated with the variation of the Qinghai Lake level, and estuary area variations were significantly negatively correlated to the lake level, indicating that the higher lake level led to more land being submerged. The evolutionary processes of lakes in the Shadao Region were influenced by aeolian sand and lake water balance experiencing relatively low precipitation and strong evaporation. Erhai Lake was also influenced by river runoff from Daotang River. Sediment loads from rivers flowing into Qinghai Lake, except for Buha River, were relative low and only slightly influenced the estuary. Aeolian sand transported by the lake waves and currents from west coast to east coast will form subaqueous barriers, the Shadao Region land area will increase slowly, and the coastline of the Shadao Region will extend towards the lake. Therefore, the diameter of Qinghai Lake from the west to east coast will become shorter, while the diameter from the south to north coast will become longer in future.