Opportunities for harnessing the increased contribution of glacier and snowmelt flows in the Ganges Basin
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Sharma, Bharat; de Condappa, D.; Bharati, Luna. 2011. Opportunities for harnessing the increased contribution of glacier and snowmelt flows in the Ganges Basin. Keynote speech presented at the International Conference on Cooperation on the Ganges: Barriers, Myths, and Opportunities, Institute of Water Policy, LKY School, National University of Singapore, Singapore, 13-14 November 2010. 16p.
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The topography of Ganges basin (GB) is much contrasted with upstream steep mountainous region of the Himalayas and downstream large fertile plains in eastern India and Bangladesh. The Himalays are partly covered by snow and glaciers that seasonally release water to the river network of GB and provide cushion against the annual fluctuations. The contribution from the glaciers to the streamflows is supposed to be significant although spatilly distributed quantification is unavailable. Moreover, there is uncertainity on the impact of climate change on glaciers and the resultant streamflows. We set up an application of the Water Evaluation and Planning (WEAP)model which contained an experimental glaciers module that accounts for snow and glaciers processes in the GB. The model also examined the possible impacts of an increase in temperature of +1, +2 or +3 degree Celsius over 20 years of the simulation period (1982-2002). The average annual stream flows in the GB that comes from melting of snow and ice in glaciated areas is significant (60-75%) in the Upper Ganga and in the Nepalese sub-basins. The share, however, reduces significantly further downstream, falling to about 19% at Farakka as flows from glaciated areas are diluted by streamflows generated by rainfall/ runoff processes. Climate change-induced rise in temperature logically increases the quantity of snow and ice that melts in glaciated areas , causing an augmentation of streamflows. However, this impact decreases from upstream ( +8% to +26% at Tehri Dam in Uttaranchal in India) to downstream (+1% to +4% at Farakka in West Bengal). Such increases in streamflows may create flood events more frequently or of higher magnitude in the Upper Ganga or in the mountainous sub-basins. In terms of water use, most of the extra water from glaciated areas do not flow when water is most required i.e. during the lean flow winter and early summer season. Potential strategy to exploit this additional water may include construction of new dams/ reservoir storages that could be used locally or within the transboundary agreements or to capture this extra water just at the end of the dry season (April-June) when flows from glaciated areas become noticeable. Enhancing the development of groundwater in the basin (from the present low level of ~ 30 per cent) through managed aquifer recharge and other suitable options shall be an equally viable option. The riparian states within India and India-Nepal- Bangladesh may harness this opportunity to alleviate physical water scarcity and transboundary water conflicts.
Keynote speech presented at the International Conference on Cooperation on the Ganges: Barriers, Myths, and Opportunities, Institute of Water Policy, LKY School, National University of Singapore, Singapore, 13-14 November 2010