Dynamics of major hydro-climatic variables in the headwater catchment of the Tarim River Basin, Xinjiang, China

We carried out an investigation on the effects of anthropogenic activities and climatic change on water resources in the Tarim River Basin, based on major hydro-climatic data, for the 1962-2007 period, and snow cover data from 2000 to 2011. A nonparametric basin-scale trend test of annual data shows a clear increasing trend for runoff, air temperature, and precipitation in the headwater catchment. We propose a copula-based approach, for studying the statistical dependence structure of hydro-climatic variables. We also constructed a two-dimensional tail estimator, to describe the nature of the tail dependence parameter, and as a means of studying its asymptotic properties. Tail dependence parameters demonstrate that air temperature has the greatest influence on runoff, followed by snow cover, precipitation, and evapotranspiration. Step-wise changes were noted to occur in the statistical dependence structure in dependence relationships, due to changes in major climate variables. Snow cover recession in the headwater catchment is consistent with the warming trend recorded by meteorological stations, but regional climate warming does not always result in snow cover reduction, owing to increased precipitation in regions such as the Aksu River basin, where a post-2000 increase in the snow cover area may have contributed to increased runoff, against a background of regional warming and wetting post-2000. Increased air temperature and precipitation, which resulted in increased runoff within the mountainous region, give rise to snowmelt and glacier-melt. Results from this study provide useful information for the planning and management of water resources in the study area.