Strategic Basin Assessment for the Ganges River Basin

Though the Ganges is one of the most populated river basins in the world, it is one of the least well understood, largely due to the lack of availability of hydrological data over much of its upstream reaches. With a group of researchers supported by the World Bank, I recently participated in a strategic basin assessment for the Ganges, work which focused on infrastructure storage options (largely in Nepal) for hydropower and flood control, economic issues related to low flows for irrigation and ecosystems (in India and Bangladesh), as well as a variety of perceived and real aspects related to the unique hydrology of this complex river system.

Main research collaborators:

  • Dale Whittington (UNC-Chapel Hill)
  • Claudia Sadoff; Nagaraja Rao Harshadeep; Jorge Escurra; Anna O’Donnell; Sylvia Lee (World Bank)
  • Don Blackmore (Consultant)
  • Wu Xun (National University of Singapore)

Related Publications:

Jeuland, M., N. Harshadeep; J. Escurra; D. Blackmore; C. Sadoff (2013). “Implications of climate change for water resources development in the Ganges basin.” Water Policy. doi:10.2166/wp.2013.107.

Abstract: 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. We 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. We 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.

Wu, X., M. Jeuland, D. Whittington, C. Sadoff (2013). “Interdependence in water resource development in the Ganges: an economic analysis.” Water Policy. doi:10.2166/wp.2013.003.

Abstract: It is often argued that the true benefits of water resource development in international river basins are undermined by a lack of consideration of interdependence in water resource planning. Yet it has not been adequately recognized in the water resources planning literature that overestimation of interdependence may also contribute to lack of progress in cooperation in many systems. This paper examines the nature and degree of economic interdependence in new and existing water storage projects in the Ganges River basin based on analysis conducted using the Ganges Economic Optimization Model. We find that constructing large dams on the upstream tributaries of the Ganges would have much more limited effects on controlling downstream floods than is thought and that the benefits of low-flow augmentation delivered by storage infrastructures are currently low. A better understanding of actual and prospective effects of interdependence not only changes the calculus of the benefits and costs of different scenarios of infrastructure development, but might also allow riparian countries to move closer to benefit sharing positions that are mutually acceptable.

Sadoff, C., N. R. Harshadeep, D. Blackmore, X. Wu, A. O’Donnell, M. Jeuland, S. Lee and D. Whittington (2013). “Ten fundamental questions for water resources development in the Ganges: myths and realities.” Water Policy. doi:10.2166/wp.2013.006.

Abstract: This paper summarizes the results of the Ganges Strategic Basin Assessment (SBA), a 3-year, multi-disciplinary effort undertaken by a World Bank team in cooperation with several leading regional research institutions in South Asia. It begins to fill a crucial knowledge gap, providing an initial integrated systems perspective on the major water resources planning issues facing the Ganges basin today, including some of the most important infrastructure options that have been proposed for future development. The SBA developed a set of hydrological and economic models for the Ganges system, using modern data sources and modelling techniques to assess the impact of existing and potential new hydraulic structures on flooding, hydropower, low flows, water quality and irrigation supplies at the basin scale. It also involved repeated exchanges with policymakers and opinion makers in the basin, during which perceptions of the basin could be discussed and examined. The study’s findings highlight the scale and complexity of the Ganges basin. In particular, they refute the broadly held view that upstream water storage, such as reservoirs in Nepal, can fully control basinwide flooding. In addition, the findings suggest that such dams could potentially double low flows in the dry months. The value of doing so, however, is surprisingly unclear and similar storage volumes could likely be attained through better groundwater management. Hydropower development and trade are confirmed to hold real promise (subject to rigorous project level assessment with particular attention to sediment and seismic risks) and, in the near to medium term, create few significant tradeoffs among competing water uses. Significant uncertainties – including climate change – persist, and better data would allow the models and their results to be further refined.