全球变化知识资源中心

Change in lake water storage is an important factor influencing hydrological cycle, regional environment, and climate on the Tibetan Plateau (TP) because of the large number (> 1000 lakes) and huge areas ( > 46,500 km(2)) of lakes. Due to the lack of in situ lake level monitoring for most lakes, and long-term continuous satellite altimetry data for some large lakes, estimates of water storage changes for all lakes throughout the TP over a long time is challenging. We have estimated the lake water storage changes of 315 lakes (each lake is > 10 km(2)) during the period of 1976-2013 through an empirical equation based on Shuttle Radar Topography Mission (SRTM) DEM (Digital Elevation Model) data and Landsat images. These lakes are located within endorheic basins and occupied approximately 80% of the total lake surface areas of the TP in 2013 based on the results of this study and Zhang et al. (2014). The results showed that the lake water storage decreased by 23.69 Gt from 1976 to 1990 and increased by 140.8 Gt from 1990 to 2013. Increased water storage was mainly concentrated in the central TP (regions A) and northern TP (region B). The increase in total lake surface area during the period 2000-2013 in region B (1981.6 km(2)) was greater than that in region A (1869.1 km(2)), but the increase in the water storage in the former was half of that in the latter, indicating that lake surface area changes cannot represent the degree of lake water storage change due to differences in the topography and lake size. Although the total variation in the rate of the lake water storage change (7.19 Gt/y) was similar to the rate of increase in the mass (7 +/- 7 Gt/y) estimated from Gravity Recovery and Climate Experiment (GRACE) data for the whole region, the spatial distribution of these variations was largely different. During the period 2000-2013, a trend analysis revealed that precipitation was perhaps the primary reason for lake change throughout the TP, while a decreasing evaporation rate only contributed approximately 1.5%, 2.5% and 1.7% to the expansions of the lakes in regions A, C and D respectively. However, based on modern glacier mass balance observation data, we estimated that glacial meltwater may have contributed 22.2%, 39.8%, 50.6% and 100% to the increasing water storage during the period 2000-2013 by rough estimates in regions A, B, C and D, respectively, indicating that glacial meltwater perhaps was a primary contributor to lake expansion in region D, which was located in an extremely cold and dry climate with a broad distribution of glaciers.