| Abstrakt: |
The hydrological response to climate change in mountainous basins manifests itself at varying spatial and temporal scales, ranging from catchment to large river basin scale and from sub‐daily to decade and century scale. To robustly assess the 21st century climate change impact for hydrology in entire High Mountain Asia (HMA) at a wide range of scales, we use a high resolution cryospheric‐hydrological model covering 15 upstream HMA basins to quantify the compound effects of future changes in precipitation and temperature based on the range of climate change projections in the Coupled Model Intercomparison Project Phase 6 climate model ensemble. Our analysis reveals contrasting responses for HMA's rivers, dictated by their hydrological regimes. At the seasonal scale, the earlier onset of melting causes a shift in the magnitude and peak of water availability, to earlier in the year. At the decade to century scale, after an initial increase, the glacier melt declines by the mid or end of the century except for the Tarim river basin, where it continues to increase. Despite a large variability in hydrological regimes across HMA's rivers, our results indicate relatively consistent climate change responses across HMA in terms of total water availability at decadal time scales. Although total water availability increases for the headwaters, changes in seasonality and magnitude may diverge widely between basins and need to be addressed while adapting to future changes in a region where food security, energy security as well as biodiversity, and the livelihoods of many depend on water from HMA. Plain Language Summary: The mountains of Asia have large reservoirs of snow and ice, which are the source of water to the people living in the mountains and downstream, mainly during the dry season. However, due to recent warming, these reserves are melting faster and depleting year by year. We use a computer model to understand what will happen to these volumes of snow and ice and the total volume of water, which also includes rain and groundwater, in the 15 main rivers under future climate change scenarios. We find that the water generated upstream will increase for all the rivers in the future. However, there would be either too little or too much water for different seasons in the future. The peak volume of water will increase in magnitude and the peak time will shift to earlier in the season (in the month of May instead of current June or July) for most rivers in the western part of Asia. This change in the timing of water will have severe impacts on the livelihoods of mountain communities as well as populations downstream where food production, energy production as well as biodiversity depend on the amount and timing of mountain water supply. Key Points: Contrasting seasonal responses are observed for High Mountain Asia's (HMA) rivers, dictated by their hydrological regimesThe onset of early snow and glacier melt in the spring season affects the magnitude and peak water availabilityA relatively consistent decadal climate change responses across HMA, despite a large variability in hydrological regimes [ABSTRACT FROM AUTHOR] |
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