Escalating lifetime water deficit for younger generations

Water scarcity is a growing concern in many regions worldwide, as demand for clean water increases and supply becomes increasingly uncertain under climate change. Developing socio-economic conditions and growing population increase water demands, while climate change leads to changes in freshwater availability. Water scarcity assessments typically rely on static biophysical measures within discrete time windows, using fixed population and climate change projections, while overlooking demographic dynamics, lifetime evolution, and cumulative deficits across generations.

Here, we calculate monthly water deficits based on sectoral, population-driven demand and water availability worldwide by combining demographic data with an ensemble of global climate and hydrological models from the InterSectoral Impact Model Intercomparison Project (ISIMIP2b). By linking these deficits with gridded population projections and life expectancy, we estimate the proportion of lifetime water demand that remains unmet per individual. Thereby we capture how shifting hydro-climatic and demographic conditions shape water scarcity across generations.

Our analysis shows that younger generations will bear a significantly greater share of lifetime water scarcity. Across all regions, younger generations will face higher lifetime water deficits compared to older generations. Without adaptation, a child born in 2020 is projected to experience 45% of their lifetime water demand unmet. Approximately 706 million children are expected to encounter deficits exceeding half of their lifetime needs—1.5 times more than individuals aged 50–59. This intergenerational disparity is primarily driven by population growth and rising life expectancy in areas with limited adaptive capacity. These findings underscore the urgent need for accelerated adaptation strategies to safeguard water security for future generations.