Human-water-GHG nexus in China: water stress assessment, mitigation and related GHG emissions within the societal water cycle
Human activities have a profound impact on water resources (water quantity and pollution induced stress) through various processes of the societal water cycle, which includes processes of water supply, treatment, distribution, residential end use, wastewater collection, treatment, reuse, and discharge. At the same time, GHG emissions are generated throughout all processes of the societal water cycle. This thesis aims to explore causes, impacts, and solutions to water stress, and its related GHG emissions within the societal water cycle in China.
Three knowledge gaps are filled in this thesis: (1). Accurate assessment of water stress; (2). Societal water cycle and its impacts on water resources, and mitigation of water stress; (3). Accurate accounting of GHG emissions of the societal water cycle (especially wastewater treatment process). The main results of this thesis show that the framework of societal water cycle provides a new insight into water stress assessment and mitigation. Water loss and return flows are main contributors to water quantity stress (36-80%). Agriculture and households are top pollution sources.
Strategies are proposed for mitigating water stress in each province by reducing water loss and return flows in the top 5 sub sectors with the greatest potential for reducing water stress (28-74%). Wastewater treatment and reuse can mitigate water stress but are insufficient. A high-resolution (firm level) and time-series (from 2006 to 2019) GHG emission inventory of wastewater treatment plants in China was developed, which serves as a crucial support for implementing GHG mitigation measures for wastewater treatment process.