The Heihe River Basin is the second largest inland river basin in the arid regions of Northwest China. Glaciers provide a large proportion of water resources for human production and living. Studies of glacier changes and their impact on water resources in the arid lands are of vital importance. A joint expedition was carried out in 2010 for investigating glaciers in the Hulugou Basin, which is located in the upper reaches of Heihe River. There- fore, glacier changes in the Hulugou Basin of central Qilian Mountains during the past 50 years were analyzed in this study by comparing topographic maps, satellite images, digital elevation models and field observation data from different periods. Results showed that the total area of the 6 glaciers in the Hulugou Basin decreased by 0.590±0.005 km^2 during the period 1956-2011, corresponding to a loss of 40.7% over the total area in 1956. The average area reduction rate of the 6 glaciers is 0.011 km^2/a. During the past five decades, the glacier shrinkage was accelerated. The changes in glacier ice surface elevation ranged from -15 to 3 m with an average thinning of 10±8 m or an annual decrease of 0.23±0.18 m （0.20±0.15 m/a water equivalent） for the period 1956-2000. The area of Shiyi Glacier in the Hulugou Basin decreased from 0.64 km^2 in 1956 to 0.53 km2 in 2011 with a reduction rate of 17.2%. The Shiyi Glacier had been divided into two separated glaciers because of severe melting. Comparative analysis showed that glacier shrinkage in the Hulugou Basin is more serious than that in the other regions of Qilian Mountains.
Many small mountain glaciers have been reported undergoing strong shrinkage, and it is therefore important to understand how they respond to climate change. The availability of topographic maps from 1962, Landsat TM imagery from 1990 and ASTER（Advanced Spaceborne Thermal Emission and Radiometer） imagery from 2006 and field investigation of some glaciers allow a comprehensive analysis of glacier change based on glacier size and topography on Mt. Bogda. Results include：（1） an overall loss of a glacierized area by 31.18±0.31 km^2 or 21.6% from 1962 to 2006,（2） a marked dependence of glacier area shrinkage on initial size, with smaller glaciers experiencing higher shrinkage levels,（3） the disappearance of 12 small glaciers,（4） a striking difference in area loss between the southern and northern slopes of 25% and 17%, respectively. A subset of the investigated glaciers shows that the area 57.45±0.73 km2 in 1962 reduced to 54.79±0.561 km^2 in 1990 and 48.88±0.49 km^2 in 2006, with a relative area reduction of 4.6% during 1962-1990, and 10.8% during 1990-2006. The corresponding volume waste increased from 6.9% to 10.2%. Three reference glaciers were investigated in 1981 and revisited in 2009. Their terminus experienced a marked recession. Meteorological data from stations around Mt. Bogda reveals that glacier shrinkage is correlated with winter warming and an extension of the ablation period. Precipitation on the northwest side of the range shows a marked increase, with a slight increase on the southeast side.
Changes in glaciers in the Chinese Tianshan Mountains have been analyzed previously. However, most previous studies focused on individual glaciers and/or decentralized glacial basins. Moreover, a majority of these studies were published only in Chinese, which limited their usefulness at the international level. With this in mind, the authors reviewed the previous studies to create an overview of glacial changes in the Chinese Tianshan Mountains over the last five decades and discussed the effects of glacial changes on water resources. In response to climate change, glaciers in the Tianshan Mountains are shrinking rapidly and are ca. 20% smaller on average in the past five decades. Overall, the area reduction of glacial basins in the central part of the Chinese Tianshan Mountains is larger than that in the eastern and western parts. The spatial differentiation in glacial changes are caused by both differences in regional climate and in glacial factors. The effects of glacial changes on water resources vary in different river basins due to the differences in glacier distribution, characteristics of glacial change and proportion of the glacier meltwater in river runoff.
WANG PuyuLI ZhongqinHUAI BaojuanWANG WenbinLI HuilinWANG Lin
