Declining glaciers endanger sustainable development of the oases along the Aksu-Tarim River (Central Asia)

Tobias Bolch,Doris Duethmann,Michel Wortmann,Shiyin Liu,Markus Disse

doi:10.1080/13504509.2021.1943723

Abstract

ABSTRACT Tarim River basin is the largest endorheic river basin in China. Due to the extremely arid climate the water supply solely depends on water originating from the glacierised mountains with about 75% stemming from the transboundary Aksu River. The water demand is linked to anthropogenic (specifically agriculture) and natural ecosystems, both competing for water. Ongoing climate change significantly impacts the cryosphere. The mass balance of the glaciers in Aksu River basin was clearly negative since 1975. The discharge of the Aksu headwaters has been increasing over the last decades mainly due to the glacier contribution. The average glacier melt contribution to total runoff is 30–37% with an estimated glacier imbalance contribution of 8–16%. Modelling using future climate scenarios indicate a glacier area loss of at least 50% until 2100. River discharge will first increase concomitant with glacier shrinkage until about 2050, but likely decline thereafter. The irrigated area doubled in the Aksu region between the early 1990s and 2020, causing at least a doubling of water demand. The current water surplus is comparable to the glacial runoff. Hence, even if the water demand will not grow further in the future a significant water shortage can be expected with declining glacial runoff. However, with the further expansion of irrigated agriculture and related industries, the water demand is expected to even further increase. Both improved discharge projections and planning of efficient and sustainable water use are necessary for further socioeconomic development in the region along with the preservation of natural ecosystems.

Highlights

The availability of water is of high importance for the sustainable development of the arid Xinjiang Uyghur Autonomous Region in north-western China, where the mean annual precipitation is less than 100 mm/a and the potential evaporation can be up to about 3000 mm/a in the lowlands (Shen and Chen 2010)
Our analysis revealed that the total water demand in our investigated area more than doubled between 1994 and 2020
The further glacier decline will lead to an initial increase of runoff of Aksu River but the runoff will very likely decline after a tipping point will be reached between 2040 and 2060

Summary

Introduction

The availability of water is of high importance for the sustainable development of the arid Xinjiang Uyghur Autonomous Region in north-western China, where the mean annual precipitation is less than 100 mm/a and the potential evaporation can be up to about 3000 mm/a in the lowlands (Shen and Chen 2010). The settlements and cities, the agricultural land and natural ecosystems depend on and compete for the river water originating from glacierised moun tains surrounding the endorheic Tarim basin (Thevs 2011; Rumbaur et al 2015; Fang et al 2018). The strong dependence on glacier melt water along with the anthropogenic development is making the Tarim basin one of the most vulnerable basins in the world (Immerzeel et al 2020). Tugai forests are a rich natural ecosystem and regulate the climate of the oasis, prevent desert expansion, protect from sand storms and are a source for firewood and timber (Thevs et al 2009; Zeng et al 2020). The area of the Tugai forests significantly decreased during the last decades as a result of the huge increase in agricultural water demand (Li et al 2013)

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