Summer hydrological characteristics in glacier and non-glacier catchments in the Nam Co Basin, southern Tibetan Plateau

Distribution of glaciers in Tibetan Plateau (TP) has been reduced during the last decades under the global warming. Understanding the hydrological features related to glacier melt is crucial for future water resource assessment as glaciers are largely experiencing strong retreat. Summer hydrological characteristics for three various scale catchments with or without glacier coverage in the Nam Co Basin over the TP for a 2-year period were investigated in this work. Angqu catchment, the largest catchment in the Nam Co Basin with a drainage area of 1479 km², is located in the west of Nam Co Basin and mainly supplied by precipitation and snowmelt. Niyaqu catchment is located in the eastern Nam Co Basin with 388 km², and its discharge is mainly supplied by precipitation and groundwater. Qugaqie catchment occupied the southern Nam Co Basin (59 km²) is a typical glacier melting supplied river. During the summer (May–September), precipitation was 533, 564, and 503 mm in Angqu, Niyaqu, and Qugaqie catchments, during 2007 and 2008, respectively. Not only the amount but also the seasonality of precipitation is different at the three catchments. In summer of 2007 and 2008, runoff was 29 and 164 mm, respectively, in Angqu; 77 and 341 mm, respectively, for Niyaqu, and 658 and 797 mm, respectively, for Qugaqie. At Niyaqu and Qugaqie, 59 and 72 % of the runoff variation was accounted by precipitation, respectively. Although there were no significant correlations between runoff and air temperature for Niyaqu and Qugaqie basins, the impact of glacier melting on the Qugaqie runoff was observed in summer.