Informing the Ganges Water Treaty: Analysis of simulated transboundary streamflow and downstream salinity in Bangladesh

Abstract:

Dry season streamflow from the Ganges river is critical for both India and Bangladesh to prevent sedimentation and salinization, respectively. In particular, salt intrusion within the Ganges delta poses risks to both agriculture and human health in Bangladesh. The Ganges Water Sharing Treaty, signed in 1996, mandates the release of streamflow to Bangladesh from India’s Farakka barrage just before the river reaches Bangladesh. The existing treaty parameters regarding water release are largely based on historical precedent rather than empirical research, in part due to limited hydrological data. With salinization continuing to threaten the delta and the treaty set to be revisited this decade, we investigate the potential of the treaty to improve freshwater deliveries and reduce salinity in Bangladesh. We simulate a variety of plausible agreements to evaluate the potential to reduce salinity burden in Bangladesh, both in terms of historical flows as well as streamflow under future climate change scenarios. We reconstructed historical daily flow at Farakka barrage using a 10-day water balance at the barrage and observed daily flow in Bangladesh under different Treaty parameters. We selected the treaties that fall on a pareto optimal frontier and explored how robust these potential treaty options were to future climate scenarios. Results provide a scientific basis for improving treaty outcomes based on the objectives of local decision makers. Preliminary findings suggest that modest and equitable changes in the flow parameters of the current treaty have the potential to reduce salinity downstream, providing a scientific basis for improving outcomes based on the objectives of local decision makers. As a next step, we plan a more rigorous analysis of the pareto optimality of such parameter changes. Although a treaty on the Ganges cannot fully alleviate salinization in the region, this research provides a basis for leveraging the impending renewal of the treaty to achieve a robust pareto-optimal outcome.