Future Secular Changes & Remediation of Groundwater Arsenic in the Ganga River Basin Arsenic in groundwater is causing severe detrimental impacts on human health in the Indian sub-continent. In the Gangetic River Basin, which supports a population of over 500 million people, tens of millions of people are exposed to groundwater arsenic, resulting in more than 15,000 premature deaths each year, as well as enhanced morbidity and reduced economic productivity.   Whilst many remediation/mitigation schemes have been implemented to reduce groundwater arsenic exposure, there exist pressures that may partly counteract these efforts. These include: [i] increased reliance on groundwater arising from increased population and affluence coupled with decreased recharge of surface water reservoirs, and [ii] future secular increases in groundwater arsenic which we hypothesise may arise from (a) ingress of surface-derived organic carbon, thought to be strongly implicated in the microbially-mediated biogeochemical processes leading to arsenic mobilisation; or (b) injection of oxygenated waters in managed aquifer recharge (MAR) leading to oxidative dissolution of arsenic-bearing pyrite   In this project, we will quantify the vulnerability of shallow urban or rural aquifers to secular increases in groundwater arsenic stimulated by enhanced oxygen or organic carbon supplies. Efficiently and effectively building on existing core research and field and laboratory infrastructure of the highly complementary team of India and UK research and water resource management investigators, this study will combine unique field studies of sedimentologically distinct natural laboratories in the upper, mid and/or lower Ganga/Hooghly as well as contrasting naturally recharging and managed aquifer recharging systems such as river bank filtration (RBF). We will evaluate the biogeochemical processes controlling arsenic mobilisation in key zones, including the hyporheic zone, of surface water-groundwater interactions. We will build upon existing detailed hydrogeological knowledge of the field areas, much built up by the project partners , supplemented by further sampling and analysis of key tracers including CFCs, SF6, tritium, and indicators of provenance, organic biomarkers, including emerging organic contaminants, and redox species ratios. Our developed understanding of these systems will be incorporated into reactive contaminated transport models to (i) facilitate the prediction of groundwater arsenic hazards in the Ganga River Basin over the next 50 years; (ii) inform selection of remediation technologies and approaches, including indirect approaches, such as improving management of near surface urban and rural organic carbon sources. Establishing workable frameworks for considering due diligence, long-term maintenance and sustainability of solutions, social integration of technology using community participatory approaches will be a key element of project outreach and knowledge transfer. The results will inform risk assessment and remediation/mitigation of groundwater vulnerability both elsewhere in India and globally, including in many ODA countries and the UK.  We have established a broad and inclusive network of researchers, NGOs, government organisations and other stakeholders with strong interests in mitigating the impacts of human activity on secular increases in the concentration of arsenic and other contaminants in vulnerable groundwaters in India.  This network will aim to both transfer knowledge of the hazard, risk and potential remediation/mitigation of these hazards as well as drive for further networking, integration, knowledge transfer and co-funding to better understand the natural and anthropogenic processes controlling these critical public health risks and effective ways to mitigate against them.    The partners have substantive and complementary track-records in this area  of research and water resource management and will bring significant co-funding to the project, through staff time and/or lab & field infrastructure. The Newton Fund builds research and innovation partnerships with developing countries across the world to promote the economic development and social welfare of the partner countries.