Lake dynamics in Tibetan Plateau during 1990-2020 and exploratory factor analyses using Google Earth Engine.

Tibetan Plateau (TP) lakes are crucial water resources for many countries, and the region is sensitive to climate change, so the TP lakes' dynamics have always been the focus of TP research. Given the vastness of the TP, the diversity of topography, geomorphology, and meteorological features, and the significant disparities in precipitation between river basins, it is vital to examine lake dynamics and influencing variables from the basin's perspective. Based on Landsat imageries and supported by Google Earth Engine, lakes were mapped from 1990 to 2020. Results show that the TP lake's number and area have increased significantly in recent 30 years except for a noticeable shrinkage from 1990 to 1995 and a slight decrease from 2013 to 2015. The lake area in the endorheic region basin area has grown obviously, with the most significant dynamics in the Qiangtang Basin, where the lake's number and total area have increased by about 30% over the 30 years. In contrast, the lake areas in the outflow region basins were relatively stable. The dynamics were obviously affected by temperature, but the influencing factors and degree of influence on different river basins vary. The lake area in the Amu Dayra Basin and the Yellow Basin was more closely related to precipitation, and the lake area in the Hexi Basin was more related to temperature. The results provide a comprehensive understanding of lake spatial-temporal dynamics in the Tibetan Plateau and its river basins and a reference for studying lake long time series.

Groundwater Storage Change in the Jinsha River Basin from GRACE, Hydrologic Models, and In Situ Data.

Groundwater plays a major role in the hydrological processes driven by climate change and human activities, particularly in upper mountainous basins. The Jinsha River Basin (JRB) is the uppermost region of the Yangtze River and the largest hydropower production region in China. With the construction of artificial cascade reservoirs increasing in this region, the annual and seasonal flows are changing and affecting the water cycles. Here, we first infer the groundwater storage changes (GWSC), accounting for sediment transport in JRB, by combining the Gravity Recovery and Climate Experiment mission, hydrologic models and in situ data. The results indicate: (1) the average estimation of the GWSC trend, accounting for sediment transport in JRB, is 0.76 ± 0.10 cm/year during the period 2003 to 2015, and the contribution of sediment transport accounts for 15%; (2) precipitation (P), evapotranspiration (ET), soil moisture change, GWSC, and land water storage changes (LWSC) show clear seasonal cycles; the interannual trends of LWSC and GWSC increase, but P, runoff (R), surface water storage change and SMC decrease, and ET remains basically unchanged; (3) the main contributor to the increase in LWSC in JRB is GWSC, and the increased GWSC may be dominated by human activities, such as cascade damming and climate variations (such as snow and glacier melt due to increased temperatures). This study can provide valuable information regarding JRB in China for understanding GWSC patterns and exploring their implications for regional water management.