Water Quality Affects Water Source Allocation and Competition Between Sectors Globally

Abstract Human activities, including domestic water use, agriculture, and energy generation, cause increasing challenges in meeting water demands, not only due to water shortages, but also poor water quality. Nevertheless, there remains limited understanding of how water quality influences the allocation of water per source across different sectors at a large scale. Here we show, for the first time, that water quality strongly affects both water source allocation and sectoral water use competition in river basins globally. We developed a new sectoral water use and allocation model, which accounts for water quality requirements (i.e., suitability thresholds) for the main water use sectors (i.e., domestic, irrigation, livestock, manufacturing and energy). Our results show that the sole inclusion of surface water quality leads to a substantial decrease of surface water withdrawal (17% globally) and an increase in groundwater dependence, with Latin America, the Middle East and North Africa exhibiting the largest responses. In addition, the inclusion of water quality requirements leads to improved estimates of total surface water used in most regions and should therefore be systematically integrated into sectoral water use modeling to provide more meaningful estimates supporting water use management and decision making.