A safe operating space for the major rivers in the Bangladesh Delta

Abstract

Abstract The contributions of water to all Sustainable Development Goals (SDGs) are critical to achieving SDGs in the context of climate change. This poses a major challenge as nearly 40% of the global population lives under water scarcity, including areas such as Bangladesh, which is one of the largest, most populous and climate-vulnerable deltas (Ganges–Brahmaputra–Meghna: GBM) in the world. Here, we aim (first attempt) to analyse the historical dynamics (spatial and temporal) of river flows in 10 major rivers and provide policy implications using a safe operating space (SOS) concept for the Bangladesh delta. In general, the space just before the unsustainable state is defined as an SOS, within which humanity can safely thrive and beyond which is dangerous to humanity. Time series analysis highlights that all seasonal river flow shows a decreasing trend in the last three decades except in the winter season. The hydrological alteration using range of variability approach confirms that the majority of the river flow has been altered high to severely including three major rivers (Ganges, Jamuna, and Old Brahmaputra) in the Bangladesh delta. Our findings show that four out of ten rivers (Ganges (dry season), Gorai, Halda and Old Brahmaputra) exceeded the SOS, with the rest of the six rivers given cautious status considering the hydrological alteration (moderate to severe) in the Bangladesh delta. Our assessment provides scientific evidence to inform science and policy related to transboundary water disputes and achieving SDGs in Bangladesh and South Asia.