Large Hydrological Processes Changes in the Transboundary Rivers of Central Asia

Abstract

Central Asia, which is one of the most complex regions in the world, is crisscrossed with transboundary rivers shared by several countries. This paper analyzes the effects of climate change and human activities on hydrological processes and water resources in these transboundary rivers over the past half century. The results show that the average temperature in the Tienshan Mountains experienced “sharp” increases in 1998, with the average temperature after 1998 being 1.0°C higher than that during 1960–1998. This rapid warming has accelerated glacier shrinkage and decreases in snow cover. These changes influenced the hydrological processes, causing an earlier runoff peak and aggravated extreme hydrological events. Changes in mountainous hydrological processes affected regional water availability and intensified future water crisis in Central Asia. The mismatched spatial distributions of water and land resources, along with the intense human activities (e.g., overexploitation of water resources), have ultimately led to the present water crisis in Central Asia's river basins. This is the main reason for ongoing water conflicts in the region's transboundary rivers and the ecological disaster of the Aral Sea.

Changes in Snow Phenology from 1979 to 2016 over the Tianshan Mountains, Central Asia

“…The maximum runoff peak in the snowmelt-dominated rivers over the TS showed an advanced trend, but the runoff in summer changed insignificantly [45]. The runoff pattern of the Syr Darya River shifted from spring and early summer to late winter and early spring due to climate warming [45]. In the Toshkan River, an important tributary of the Aksu River, snowmelt runoff in the cold season increased by 65% and 56% due to the rising temperatures during the periods from 1960 to 1997 and from 1998 to 2015 [45,85], respectively.…”

“…The advanced D e , with increased precipitation in the upper reaches of the Aksu, Syr Darya, Kaidu, and the Ili Rivers contributed to increased snowmelt earlier in spring. The maximum runoff peak in the snowmelt-dominated rivers over the TS showed an advanced trend, but the runoff in summer changed insignificantly [45]. The runoff pattern of the Syr Darya River shifted from spring and early summer to late winter and early spring due to climate warming [45].…”

“…The main rivers that are recharged by glacier/snow melt water (e.g., the Ili River, Syr Darya River, Amu Darya River, Tarim River, and Chu River) originate from the TS, forming one of the largest irrigated zones in the world [41][42][43]. Previous studies indicated that the TS have experienced a significant warming trend over the past few decades [44][45][46]. The snowfall/precipitation ratio showed a decreasing trend accompanied by increasing temperatures in the TS [47], which intensified glacier and snow melt [2], leading to increasing runoff and earlier peak runoff from glacier/snow melt in these recharging river basins [45,[48][49][50].…”

“…Previous studies indicated that the TS have experienced a significant warming trend over the past few decades [44][45][46]. The snowfall/precipitation ratio showed a decreasing trend accompanied by increasing temperatures in the TS [47], which intensified glacier and snow melt [2], leading to increasing runoff and earlier peak runoff from glacier/snow melt in these recharging river basins [45,[48][49][50]. Several studies have investigated the impact of glacier change on water resources in the TS [42,51-53], but only a few studies have addressed the snow cover changes with optical remote sensing [54,55].…”

In Water‐Limited Landscapes, an Anthropocene Exchange: Trading Lakes for Irrigated Agriculture

“…Among Earth's terminal lakes this analysis identifies the Aral Sea as having experienced the most extensive areal shrinkage (Figure 2) “overwhelmingly” due to increases in agricultural area (Micklin, 1988; Micklin, 2007; Micklin, 2016), which have continued despite the Sea's rapid shrinkage (Chen et al, 2018). Also in Asia, the shrinkage of Lake Urmia, Iran, has been contested, with claims of the importance of climatic factors discredited relative to overexploitation for irrigated agriculture (AghaKouchak et al, 2015; Alborzi et al, 2018; Chaudhari et al, 2018; Fazel et al, 2017; Ghale et al, 2018; Khazaei et al, 2019; Madani, 2014; Madani et al, 2016; Taravat et al, 2016; Tourian et al, 2015).…”