Multi-hazard groundwater risks to water supply from shallow depths: challenges to achieving the sustainable development goals in Bangladesh

Background: 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. Methods: 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 socio-economic variables including access to drinking and irrigation water supplies and social vulnerability (i.e., poverty) are overlaid on these risk maps to estimate exposures. Results: Our multi-parameter groundwater hazard maps show that a considerable proportion of land area (5% to 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. Conclusions: 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 policymakers 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

Megacity pumping and preferential flow threaten groundwater quality

Many of the world’s megacities depend on groundwater from geologically complex aquifers that are over-exploited and threatened by contamination. Here, using the example of Dhaka, Bangladesh, we illustrate how interactions between aquifer heterogeneity and groundwater exploitation jeopardize groundwater resources regionally. Groundwater pumping in Dhaka has caused large-scale drawdown that extends into outlying areas where arsenic-contaminated shallow groundwater is pervasive and has potential to migrate downward. We evaluate the vulnerability of deep, low-arsenic groundwater with groundwater models that incorporate geostatistical simulations of aquifer heterogeneity. Simulations show that preferential flow through stratigraphy typical of fluvio-deltaic aquifers could contaminate deep (>150 m) groundwater within a decade, nearly a century faster than predicted through homogeneous models calibrated to the same data. The most critical fast flowpaths cannot be predicted by simplified models or identified by standard measurements. Such complex vulnerability beyond city limits could become a limiting factor for megacity groundwater supplies in aquifers worldwide.National Institute of Environmental Health Sciences. Superfund Research Program (Grant P42 ES010349)National Science Foundation (U.S.) (Grant EAR-115173

Sediment Delivery to Sustain the Ganges-Brahmaputra Delta Under Climate Change and Anthropogenic Impacts

The principal nature-based solution for offsetting relative sea-level rise in the Ganges-Brahmaputra delta is the unabated delivery, dispersal, and deposition of the rivers’ ~1 billion-tonne annual sediment load. Recent hydrological transport modeling suggests that strengthening monsoon precipitation in the 21st century could increase this sediment delivery 34-60%; yet other studies demonstrate that sediment could decline 15-80% if planned dams and river diversions are fully implemented. We validate these modeled ranges by developing a comprehensive field-based sediment budget that quantifies the supply of Ganges-Brahmaputra river sediment under varying Holocene climate conditions. Our data reveal natural responses in sediment supply comparable to previously modeled results and suggest that increased sediment delivery may be capable of offsetting accelerated sea-level rise. This prospect for a naturally sustained Ganges-Brahmaputra delta presents possibilities beyond the dystopian future often posed for this system, but the implementation of currently proposed dams and diversions would preclude such opportunities

Potential Impacts of Industrialization on Coastal Fresh Groundwater Resources in Bangladesh

Bangladesh is overly dependent on groundwater and the demand in the near future is expected to increase, as the country is experiencing rapid development and industrial growth. This study assesses the prospect and sustainability of groundwater in Mirsharai Upazila, Chattogram, where a large industrial area, namely ‘Bangabandhu Sheikh Mujib Shilpa Nagar (BSMSN)’, is taking shape. The physical aquifer system was characterized and groundwater quality was mapped. There is one thick aquifer in the northernmost part of the upazila, which splits into three separate aquifers in the south. Water quality indexing suggests that the deep (>130 m) groundwater throughout upazila is good (n = 5) to excellent (n = 18), while the shallow groundwater is mostly poor to unsuitable for both drinking and irrigation purposes. Because of the close proximity to the sea and the presence of thick clays above the deep freshwater aquifer in the BSMSN area, heavy industrial abstraction poses a threat to the lateral intrusion of seawater and land subsidence. Even a small subsidence in the project area at only a couple of meters above sea level would jeopardize the entire project. This study recommends limiting the use of the deep fresh groundwater for the current population of the upazila

Wheat blast: a new threat to food security

Wheat blast, caused by the Magnaporthe oryzae Triticum (MoT) lineage (synonym Pyricularia oryzae Triticum lineage), is a destructive disease in South America and Bangladesh. It is primarily a disease of wheat head, which can cause yield loss up to 100% under favorable disease conditions. The head infection results in complete or partial bleaching of the spike above the point of infection with either no grain or shriveled grain with low test weight. Due to low fungicide efficacy against the disease and lack of availability of resistant varieties, an integrated management program should be adopted to control this serious wheat disease. First of all, a convenient and specific diagnostic tool is needed for evaluating seed health and early detection in wheat field to initiate timely mitigation measures and thereby decreasing pathogen initial inoculum and dispersal. Second, we should have a better understanding of the epidemiology of the disease and develop a real-time disease monitoring and surveillance system to alert growers to apply management practices at an optimum time. Third, we need a better understanding of the infection biology of the fungus and its interaction with wheat plants at the tissue and molecular levels helpful for improving disease management. Fourth, breeding for resistance to wheat blast can be accelerated by using resistance genes such as 2NS translocation, Rmg8 and RmgGR119 or advanced genomic technology such as CRISPR-Cas. Fifth, integration of alternative disease management practices, such as biological control using antagonistic microorganisms or derivatives thereof to achieve sustainable approach for the management of wheat blast. Finally, a globally concerted effort is needed using open science and open data sharing approaches to prevent this seed- and air-borne plant disease’s widespread devastation of wheat crop. This comprehensive review updates our knowledge on wheat blast disease and discusses the approaches for its sustainable management for ensuring food and nutritional security of the ever-increasing global population