Contrasting Fate of Western Third Pole's Water Resources Under 21st Century Climate Change

Abstract

Seasonal melting of glaciers and snow from the western Third Pole (TP) plays important role in sustaining water supplies downstream. However, the future water availability of the region, and even today's runoff regime, are both hotly debated and inadequately quantified. Here, we characterize the contemporary flow regimes and systematically assess the future evolution of total water availability, seasonal shifts, and dry and wet discharge extremes in four most meltwater‐dominated basins in the western TP, by using a process‐based, well‐established glacier‐hydrology model, well‐constrained historical reference climate data, and the ensemble of 22 global climate models with an advanced statistical downscaling and bias correction technique. We show that these basins face sharply diverging water futures under 21st century climate change. In RCP scenarios 4.5 and 8.5, increased precipitation and glacier runoff in the Upper Indus and Yarkant basins more than compensate for decreased winter snow accumulation, boosting annual and summer water availability through the end of the century. In contrast, the Amu and Syr Darya basins will become more reliant on rainfall runoff as glacier ice and seasonal snow decline. Syr Darya summer river‐flows, already low, will fall by 16%–30% by end‐of‐century, and striking increases in peak flood discharge (by >60%), drought duration (by >1 month) and drought intensity (by factor 4.6) will compound the considerable water‐sharing challenges on this major transboundary river.

Reviving the Aral Sea: A Hydro‐Eco‐Social Perspective

“…Similar trends have also been reported in recent studies, for example, Su et al. (2022). For the whole Aral Sea basin, runoff is projected to reach 115.8 ± 12.3 km 3 /year during 2021–2050 and 117.2 ± 13.8 km 3 /year in 2071–2100 (Figure 3d).…”

“…Compared with the period 1986-2015, the annual mean runoff of the Amu Darya River is projected to increase by 6.3-8.8 km 3 /year (8.3%-11.7%) in the near future (2021-2050) and 7.8-12.1 km 3 /year (10.4%-16.1%) later in the century (2071-2100), while that of the Syr Darya River will increase by 4.2-6.2 km 3 /year (15.0%-21.8%) in 2021-2050 and 3.7-6.8 km 3 /year (13.0%-24.2%) in 2071-2100 under the ssp126, ssp245, and ssp585 scenarios, respectively. Similar trends have also been reported in recent studies, for example, Su et al (2022).…”

Surface Motion and Topographic Effects on Ice Thickness Inversion for High Mountain Asia Glaciers: A Comparison Study from Three Numerical Models

“…The latest release of the Glacier Thickness Database (GlaThiDa v3) included only 4000 glaciers worldwide [12]. For ~200,000 glaciers globally, HMA, which consists of the Tibetan Plateau and its surrounding mountain ranges (including the Himalayas, Karakoram Range, Tien Shan Range, and Pamir Range), has the highest concentration of glaciers outside the poles, and is therefore known as the "Third Pole" [31]. These glaciers are the headwater of many rivers, such as the Yangtze River, the Brahmaputra, and the Lancang River.…”

Unveiling the Future Water Pulse of Central Asia: A Comprehensive 21st Century Hydrological Forecast from Stochastic Water Balance Modeling

“…The paucity of in-situ data for hydrological model calibration and validation in the region has traditionally forced regional studies to work at the level of the large river basins only (see, e.g., Khanal et al 2021;Su et al 2022). However, as Fig.…”