Unravelling global water scarcity by modelling the interplay of sectoral water use and water quality including droughts. Too little or too dirty?

Human activities strongly rely on sufficient water of adequate quality, yet major water use sectors such as domestic, irrigation, livestock, manufacturing and energy increasingly experience clean water scarcity. These pressures arise from climate‑induced shifts in hydrology, rising water demands driven by population growth, and the deterioration of water quality caused by pollution from multiple sectors. Together, these factors constrain the availability of water of suitable quality and intensify cross‑sectoral competition for clean water. Although recent efforts have started to integrate water quality into global water scarcity assessments, limited knowledge exists on how individual sectors respond to clean water scarcity and on how these responses are shaped by the interplay among the various drivers of water scarcity. This challenge is further compounded by extreme hydroclimatic events like droughts and heatwaves, which reduce water availability, increase sectoral demands, and worsen water quality through both natural processes (e.g., higher water temperatures, concentration) and intensified human pressures.

Despite extensive research on water scarcity, the role of these driving mechanisms and their combined effects on sectoral water use remain insufficiently understood, particularly under drought and heatwave conditions, which are projected to become more frequent, intense, and longer lasting in several regions. Addressing these gaps requires extensive and detailed information on sectoral water use and their interplay with water quality and availability, at different spatiotemporal resolutions, yet available reported data remain insufficient for comprehensive assessments of clean water scarcity. Additionally, existing global datasets and models do not explicitly capture the dynamics of water allocation across sectors or their specific responses to clean water limitations. Consequently, current global clean water scarcity assessments provide limited insight into how water quality requirements influence water scarcity across water use sectors under global change. These knowledge gaps motivate the overarching research objective of this PhD thesis:

Estimate the response of sectoral water use under extreme hydroclimatic events and their interaction with water quality to unravel sector-specific water scarcity. […]