The water balance calculations were carried out at 6' (longitude × latitude) spatial resolution using version 6.01 of the Simulated Topological Network (STN30p), a modestly updated version of the dataset presented in Vörösmarty et al. (6). The water balance/transport model applied in the present study (WBMplus) is an updated version of the global water balance model that was developed by Vörösmarty et al. (7, 8) and subsequently modified by Wisser et al. (9, 10). Input data on precipitation and temperature use are fed into the model, as well as a hydrologic network based on a digital elevation model. Evapotranspiration is calculated as a function of local land use, including consumptive water use by agriculture.