Changes in Central Asia's Water Tower: Past, Present and Future.

Yaning Chen,Gonghuan Fang,Weihong Li,Zhi Li,Haijun Deng

doi:10.1038/srep35458

Abstract

The Tienshan Mountains, with its status as “water tower”, is the main water source and ecological barrier in Central Asia. The rapid warming affected precipitation amounts and fraction as well as the original glacier/snowmelt water processes, thereby affecting the runoff and water storage. The ratio of snowfall to precipitation (S/P) experienced a downward trend, along with a shift from snow to rain. Spatially, the snow cover area in Middle Tienshan Mountains decreased significantly, while that in West Tienshan Mountains increased slightly. Approximately 97.52% of glaciers in the Tienshan Mountains showed a retreating trend, which was especially obvious in the North and East Tienshan Mountains. River runoff responds in a complex way to changes in climate and cryosphere. It appears that catchments with a higher fraction of glacierized area showed mainly increasing runoff trends, while river basins with less or no glacierization exhibited large variations in the observed runoff changes. The total water storage in the Tienshan Mountains also experienced a significant decreasing trend in Middle and East Tienshan Mountains, but a slight decreasing trend in West Tienshan Mountains, totally at an average rate of −3.72 mm/a. In future, water storage levels are expected to show deficits for the next half-century.

Highlights

The Tienshan Mountains, with its status as “water tower”, is the main water source and ecological barrier in Central Asia
Winter increases in precipitation were especially notable in West Tienshan Mountains, rising 23% over the past 55 years (Fig. 1g)
Based on Gravity Recover and Climate Experiment (GRACE) data of terrestrial total water storage (TWS) variations in the Tienshan Mountains in 2003–2013, the results indicate a decreasing trend in TWS, with a decline rate of −3 .72 mm/a (Fig. 6)

Summary

Introduction

The Tienshan Mountains, with its status as “water tower”, is the main water source and ecological barrier in Central Asia. In regions where water resources are dominated by glacier and snow melt from mountains, the availability is more complicated Water supplies in these areas are strongly related to changes in temperature and precipitation, as well as changes in the snow and ice distributed across the mountains. Previous studies showed that most regions have experienced a warming trend, and that the average global temperature has increased 0.7 °C over the past hundred years[13] This warming trend is especially obvious in the Tienshan Mountains[14], where the average annual warming rate over the past half-century has been 0.34 °C/10a15. This may result in the feedback effects of reduced glacier/snow surface albedo, which will break the surface glacier energy and mass balance, and cause serious changes in the local water cycle

Methods

Results

Conclusion