Multi-hazard Groundwater Risks to Water Supply from Shallow Depths: Challenges to Achieving the Sustainable Development Goals in Bangladesh

Groundwater currently provides 98% of all drinking-water supply in Bangladesh. Groundwater is found throughout Bangladesh but its quality (i.e., arsenic and salinity contamination) and quantity (i.e., water-storage depletion) vary across hydrological environments, posing unique challenges to certain geographical areas and population groups. Yet, no national-scale, multi-parameter groundwater hazard maps currently exist enabling water resources managers and policy makers to identify vulnerable areas to public health. We develop, for the first time, groundwater multi-hazard maps at the national scale of Bangladesh combining information on arsenic, salinity, and water storage. We apply geospatial techniques in 'R' programming language and ArcGIS environment, linking hydrological indicators for water quality and quantity to construct risk maps. A range of socioeconomic variables including access to drinking and irrigation water supplies and social vulnerability (i.e., poverty) are overlaid on these risk maps to estimate exposures. Our multi-parameter groundwater hazard maps show that a considerable proportion of land area (5-24% under extremely high to high risks) in Bangladesh is currently under combined risk of arsenic and salinity contamination, and groundwater-storage depletion. As small as 6.5 million (2.2 million poor) to 24.4 million (8.6 million poor) people are exposed to a combined risk of high arsenic, salinity, and groundwater-storage depletion. Our groundwater hazard maps reveal areas and exposure of population groups to water risks posed by arsenic and salinity contamination and depletion of water storage. These geospatial hazard maps can potentially guide policy makers in prioritizing mitigation and adaptation measures in order to achieve the United Nation's Sustainable Development Goals across the water, agriculture, and public health sectors in Bangladesh.