Characteristics of climate and melt runoff in the Koxkar Glacier River Basin, south slope of the Tianshan Mountains, Northwest China

Hydrology of the high glacierized region in the Tianshan Mountains is an important water resource for arid and semiarid areas of China, even Central Asia. The hydrological process is complex to understand, due to the high variability in climate and the lack of hydrometeorological data. Based on field observations, the present study analyzes the meteorological and hydrological characteristics of the Koxkar Glacier River Basin during 2008-2011; and the factors influencing climate impact on glacier hydrology are discussed. The results show that precipitation at the terminus of the glacier was 426.2 mm, 471.8 mm, 624.9 mm, and 532 mm in 2008, 2009, 2010, and 2011, respectively. Discharge increases starting in May,reaches its highest value in July and August, and then starts to decrease. The mean annual discharge was 118.23×106 m~3 during the four years observed, with 87.0% occurring in the ablation season(May-September). During the study period,the runoff in August accounted for 29% of total streamflow, followed by July(22%) and June(14%). The runoff exhibited obviously high interannual variability from April to September, induced by drastic changes in climate factors. Discharge autocorrelations are very high for all the years. The climate factors show different influences on discharge. The highest correlation R between daily temperature and discharge was for a time lag of 2-3 days on the Koxkar Glacier(0.66-0.76).The daily depth of runoff to daily temperature and daily water vapor pressure had an R~2 value of 0.56 and 0.69, respectively, which could be described by an exponential function. A closer relationship is found between runoff and either temperature or water vapor pressure on a monthly scale; the R~2 values are 0.65 and 0.78, respectively. The study helps us to understand the mechanisms of the hydrological-meteorological system of typical regional glaciers and to provide a reference for glacier-runoff simulations and water-resource management.