Implications of Climate Change for Water Resources Development in the Ganges Basin

This paper presents the first basin-wide
assessment of the potential impact of climate change on the
hydrology and production of the Ganges system, undertaken as
part of the World Bank’s Ganges Strategic Basin Assessment.
A series of modeling efforts, downscaling of climate
projections, water balance calculations, hydrological
simulation and economic optimization, inform the assessment.
The authors find that projections of precipitation across
the basin, obtained from 16 Intergovernmental Panel on
Climate Change-recognized General Circulation Models are
highly variable, and lead to considerable differences in
predictions of mean flows in the main stem of the Ganges and
its tributaries. Despite uncertainties in predicted future
flows, they are not, however, outside the range of natural
variability in this basin, except perhaps at the tributary
or sub-catchment levels. The authors also find that the
hydropower potential associated with a set of 23 large dams
in Nepal remains high across climate models, largely because
annual flow in the tributary rivers greatly exceeds the
storage capacities of these projects even in dry scenarios.
The additional storage and smoothing of flows provided by
these infrastructures translates into enhanced water
availability in the dry season, but the relative value of
this water for the purposes of irrigation in the Gangetic
plain, and for low flow augmentation to Bangladesh under
climate change, is unclear.