Abstract
The Indus basin heavily depends on its upstream mountainous part for the downstream supply of water while downstream demands are high. Since downstream demands will likely continue to increase, accurate hydrological projections for the future supply are important. We use an ensemble of statistically downscaled CMIP5 General Circulation Model outputs for RCP4.5 and RCP8.5 to force a cryospheric-hydrological model and generate transient hydrological projections for the entire 21st century for the upper Indus basin. Three methodological advances are introduced: (i) A new precipitation dataset that corrects for the underestimation of high-altitude precipitation is used. (ii) The model is calibrated using data on river runoff, snow cover and geodetic glacier mass balance. (iii) An advanced statistical downscaling technique is used that accounts for changes in precipitation extremes. The analysis of the results focuses on changes in sources of runoff, seasonality and hydrological extremes. We conclude that the future of the upper Indus basin’s water availability is highly uncertain in the long run, mainly due to the large spread in the future precipitation projections. Despite large uncertainties in the future climate and long-term water availability, basin-wide patterns and trends of seasonal shifts in water availability are consistent across climate change scenarios. Most prominent is the attenuation of the annual hydrograph and shift from summer peak flow towards the other seasons for most ensemble members. In addition there are distinct spatial patterns in the response that relate to monsoon influence and the importance of meltwater. Analysis of future hydrological extremes reveals that increases in intensity and frequency of extreme discharges are very likely for most of the upper Indus basin and most ensemble members.
Highlights
The water resources supplied by the upper Indus basin (UIB) are essential to millions of people and future changes in both demand and supply may have large impacts [1]
The trends, and large uncertainties of precipitation change we find in our ensembles are similar to what was found in an analysis of 32 CMIP5 GCMs over the Hindu-Kush-Karakoram-Himalaya region [42], and once more demonstrate the need for improvement of climate simulations in this region, to lower the uncertainty in the future’s climate
This study stands out from previous work as for the first time shifts in seasonal water availability are assessed in combination with changes in hydrological extremes at basin scale for the upper Indus basin
Summary
The water resources supplied by the upper Indus basin (UIB) are essential to millions of people and future changes in both demand and supply may have large impacts [1]. Upper Indus Hydrology and Climate Change and the International Development Research Centre (IDRC), Ottawa, Canada DFID partly funds ICIMOD’s Indus Basin Programme, under which this study was undertaken These funds partly supported the contributions of AFL, WWI and ABS. DFID and IDRC funds the HI-AWARE consortium, of which ICIMOD and FutureWater are consortium members FutureWater provided support in the form of salaries for authors AFL and WWI, but did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. The specific roles of these authors are articulated in the ‘author contributions’ section
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
