Global assessment of how reservoirs and desalination plants enhance human water security

Water scarcity arises not only from chronic water shortage but also from seasonal and interannual variability. Water infrastructure fills the gaps in water requirements and sustainably available water. However, its role in mitigating water deficits and the differences across regions have been insufficiently explored. Here, we quantify the contribution of reservoirs and desalination plants (RDs) in reducing water deficits using a global hydrological model and indicators that capture spatiotemporal dynamics. We find that RDs substantially reduce global water deficits and that their functions vary regionally: seasonal reallocation dominates in Asian monsoon regions, whereas interannual buffering is more prominent in regions of the Southern Hemisphere. Globally, RDs alleviate water deficits equivalent to more than 5% of the global human water requirements on average and over 13% during drought periods. These findings provide a quantitative assessment of how water infrastructure contributes to water security across regions with differing hydroclimatic and socioeconomic conditions.