LAUSR

Abstract This study investigated the contributions of snow/glacier meltwater to river runoff in the northern and central Tianshan Mountains (Central Asia). Based on end- member mixing analysis (EMMA), the hydrograph separation was carried out in six benchmark catchments with different glacier area ratios (GARs) and snow area ratios (SARs) during a typical snow melt period (TSMP) and a typical glacier melt period (TGMP). The results indicate that the contribution of snow/glacier meltwater to river runoff is positively correlated with GARs or maximum SARs. The contribution ratios of snowmelt water vary from 22% to 49% in TSMP. The contribution ratios of glacier meltwater vary from 12% to 59% in TGMP. The contribution ratios of snow meltwater in the northern Tianshan Mountains (36%) are higher than central Tianshan Mountains (31%), while the contribution ratios of glacier meltwater in the northern Tianshan Mountains (36%) are lower than central Tianshan Mountains (42%). The contribution of rainfall to river runoff is higher in TGMP (9%–23%) than in TSMP (5%–9%). Baseflow is the most important recharge source to river runoff, with the contribution ratios vary from 44% to 73% in TSMP, and vary from 30% to 75% in TGMP. The spatial and temporal variations in tracer concentrations in streamflow components were found to be responsible to the uncertainties in hydrograph separation.