Five decades of glacier changes in the Hulugou Basin of central Qilian Mountains, Northwest China

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. Therefore, 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 km(2) 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.