Delineating city boundaries for global urban water scarcity assessment

Rapid urbanisation has increased water demand in cities worldwide and global urban water scarsity assessments should be conducted using global gridded hydrological information. We developed Hydro Urban Map (HUM), a global dataset of city boundaries for 1,604 cities at 5 arcmin resolution. HUM delineates city masks and integrates information relevant to urban water supply and drainage. The dataset combines geographical data, allowing the identification of the uppermost and lowermost grid cells along each city's main river, which are designated as the city water inlet and the city water outlet, respectively. Additionally, HUM identifies the origin of the aqueduct by selecting the grid cell with the highest annual astream flow near the city mask.