CLIMATE AND STREAMFLOW CHANGES IN THE AMU DARYA BASIN, CENTRAL ASIA

Abstract:

Amu Darya River is located in the central Asia and flows through Tajikistan, Afghanistan, Kirgizstan, Uzbekistan and Turkmenistan before emptying into the Aral Sea. In the source region on the Pamir, the river basin contains the Fedchenko glacier, the largest mountain glacier in the world. Glacier, snow and precipitation in the high mountain area are the major streamflow contributors. Due to mismanagement and climate change since 1960s, the area of the Aral Sea shrank sharply and its changes caused a series of severe environmental issues. As an important water resource for the region, a comprehensive and systematic analysis of climate and streamflow changes of the Amu Darya Basin is important. However studies of climate change and streamflow change and its mechanisms are limited up to date.

In this study we will utilized observed and gridded climate and streamflow and a macro-scale hydrological model coupled with an empirical glacial model to analyze the changes in climate and streamflow. Hydrological models are powerful tools for simulating the land surface hydrological processes and thus streamflow changes. A degree-day glacier-melt scheme coupled with the Variable Infiltration Capacity (VIC) macro-scale hydrological model is used for the investigation. The combined model is set up at 0.25°×0.25° grids and applied in the Amu Darya basin. The model was validated with the observed monthly streamflow of nine hydrological stations in the upper Amu Darya. The model showed an acceptable performance, with R² of 0.76–0.92, Nash-Sutcliffe efficiency of 0.74–0.92, ratio of the root mean square error to the standard deviation (RSR) of 0.29–0.51, PBIAS of -9.25%-10.65% for the complete simulation period. Performance ratings for these quantitative statistics suggested that the VIC-glacier model has a good potential of broader utility for the large basins. Within this model framework, we will first examine the mechanisms of streamflow change for the upper Amu Darya basin in the historical period in the mountainous region. Secondly, we will quantify the contributions of rainfall, snowmelt, and glacier melt to the streamflow in the upper Amu Darya basin in dry, wet and normal years for historical period. These results will provide scientific support for the sustainable management and development of water resources in the basin.