Study on Characteristics of Water Level Variations and Water Balance of the Largest Lake in the Qinghai-Tibet Plateau

Abstract

Qinghai Lake is the largest lake in Qinghai-Tibet Plateau and China, it is also an important part of the national ecological security strategy. Since 1950s, the water level of Qinghai Lake has been changing rapidly, which induces great effects on the surrounding traffic facilities, residents’ safety and the development of animal husbandry, etc. Therefore, it is necessary to study the water level evolution and water balance of Qinghai Lake under the main impact of climate change. Based on meteorological and hydrological data from Buha River Hydrological Station, Xiashe Hydrological Station, and Gangcha Meteorological Station, CMFD, and water balance equation, this article first analyzes the interannual and intra-year water level evolution characteristics of Qinghai Lake from 1956 to 2020, including lake surface precipitation (P), runoff into the lake (Rs) and evaporation (E). Secondly, we conducted a study on the water level change characteristics calculated for fixed months. Finally, the contribution rate of each factor to the fluctuation of Qinghai Lake water level was quantitatively calculated using the ridge regression method. Results show that the annual average water level declined at a rate of 0.8 m decade−1 from 1956 to 2004, primarily due to E exceeding the sum of P and Rs. However, from 2004 to 2020, the water level increased at a rate of 1.7 m decade−1, mainly attributed to the increase in P and Rs. Qinghai Lake exhibits evident intra-year variations, with the water level starting to rise in May and reaching its peak in September, which aligns with the monthly variations of Rs, P, and E. Furthermore, the impacts of the current year’s P, Rs, and E on the annual water level fluctuations for fixed months of September to December is greater than that of the previous year. Specifically, the contributions of the current year’s P, Rs and E to the water level fluctuations calculated based on December data are 10%, 70%, and 20%, respectively. The contribution rate of meteorological factors to the rise and fall of water level was wind speed (33%), downward short-wave radiation (27%), precipitation (27%), downward long-wave radiation (11%) and specific humidity (2%).