Climate Change Impacts on the Upper Indus Hydrology: Sources, Shifts and Extremes

PLOS ONE, Dec 2019

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.

A PDF file should load here. If you do not see its contents the file may be temporarily unavailable at the journal website or you do not have a PDF plug-in installed and enabled in your browser.

Alternatively, you can download the file locally and open with any standalone PDF reader:

https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0165630&type=printable

Climate Change Impacts on the Upper Indus Hydrology: Sources, Shifts and Extremes

November Climate Change Impacts on the Upper Indus Hydrology: Sources, Shifts and Extremes A. F. Lutz 0 1 W. W. Immerzeel 0 1 P. D. A. Kraaijenbrink 1 A. B. Shrestha 1 M. F. P. Bierkens 1 0 FutureWater , Costerweg 1V, 6702 AA, Wageningen , The Netherlands , 2 Utrecht University, Department of Physical Geography , PO Box 80115, 3508 TC, Utrecht , The Netherlands , 3 International Centre for Integrated Mountain Development , GPO Box 3226, Khumaltar, Kathmandu , Nepal 1 Editor: Juan A. Añel, Universidade de Vigo , SPAIN 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. - Funding: This study was undertaken under the Indus Basin Programme of ICIMOD, funded in part by the United Kingdom's Department for International Development (DFID), through their financial support of core research at ICIMOD. This work is partly carried out by the Himalayan Adaptation, Water and Resilience (HI-AWARE) consortium under the Collaborative Adaptation Research Initiative in Africa and Asia (CARIAA) with financial support from the United Kingdom's Department for International Development (DFID) Introduction 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 UIB provides water for the world's largest continuous irrigation scheme through several large reservoirs (e.g. and the International Development Research Centre (IDRC), Ottawa, Canada. This project has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (grant agreement 676819). In addition, this work was partially supported by core funds of ICIMOD contributed by the governments of Afghanistan, Australia, Austria, Bangladesh, Bhutan, China, India, Myanmar, Nepal, Norway, Pakistan, Switzerland, and the United Kingdom. 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. These funds partly supported the contributions of AFL, WWI and ABS. ERC partly funded the contribution of WWI through grant agreement 676819. ICIMOD core funds partly funded the contribution of ABS. AFL and WWI are employed by FutureWater. 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. Competing Interests: We have read the journal's policy and the authors of this manuscript have the following competing interests: AFL and WWI are employed by FutureWater. There are no patents, products in development or marketed products to declare. This does not alter our adherence to all the PLOS ONE policies on sharing data and materials. the Tarbela and Mangla dams, Fig 1), which depend for more than 50% of their annual inflow on snow and glacier melt water [ 2–5 ]. In combination with varia (...truncated)


This is a preview of a remote PDF: https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0165630&type=printable

A. F. Lutz, W. W. Immerzeel, P. D. A. Kraaijenbrink, A. B. Shrestha, M. F. P. Bierkens. Climate Change Impacts on the Upper Indus Hydrology: Sources, Shifts and Extremes, PLOS ONE, 2016, Volume 11, Issue 11, DOI: 10.1371/journal.pone.0165630