Abstract
Human activities greatly impact surface water quality, while being reliant upon it for water supply. Surface water quality is expected to change in the future as a result of alterations to pollutant loadings, surface water withdrawals and hydrological regimes, driven by both climate change and socio-economic developments. Here we use a high-resolution global surface water quality model to project water temperature and indicators of salinity (total dissolved solids), organic (biological oxygen demand) and pathogen (fecal coliform) pollution until 2100. The results show that while surface water quality, as indicated by these pollutants, will improve in most advanced economies, the outlook for poorer nations is bleak. The proportion of the global population exposed to salinity, organic and pathogen pollution by the end of the century ranges from 17 to 27%, 20 to 37% and 22 to 44%, respectively, with poor surface water quality disproportionately affecting people living in developing countries. Exhibiting the largest increases in both the absolute and relative number of people exposed, irrespective of climate change and socio-economic development scenario, we conclude that Sub-Saharan Africa will become the new hotspot of surface water pollution globally.