Partitioning the contributions of glacier melt and precipitation to the 1971–2010 runoff increases in a headwater basin of the Tarim River

Glacier retreat and runoff increases in the last few decades characterize conditions in the Kumalak River Basin, which is a headwater basin of the Tarim River with a catchment area of 12,800 km2. To address the scientific question of whether, and to what extent, the observed runoff increase can be attributed to enhanced glacier melt and/or increased precipitation, a glacier evolution scheme and precipitation-runoff model are developed. Using the glacio-hydrological model, we find that both glacier cover area and glacier mass in the study area have decreased from 1971 to 2010. On average, the contribution to total runoff from rainfall, glacier melt and snowmelt are 60.6%, 28.2% and 11.2%, respectively. Despite covering only 21.3% of the basin area, glacier areas contributed 43.3% (including rainfall, snowmelt and glacier melt) to the total runoff from our model estimates. Furthermore, as primary causes of increased runoff in response to the warmer and wetter climate over the period 1971–2010, contribution from increases in rainfall and glacier melt are 56.7% and 50.6%, respectively. In comparison to rainfall and glacier melt, snowmelt has a minor influence on runoff increase, accounting for −7.3%. The research has important implications for water resources development in this arid region and for some similar river basins in which glacial melt forms an important part of the hydrological cycle