Hydrology and Earth System Sciences | Bosmans et al. 
Human impacts on global terrestrial hydrology have been accelerating during the 20th century. These human impacts include the effects of reservoir building and human water use, as well as land cover change. To date, many global studies have focussed on human water use, but only a few focus on or include the impact of land cover change. Here we use the global hydrological and water resources model PCR-GLOBWB to assess the impacts of land cover change as well as human water use. Our results show that land cover change has a strong effect on the global hydrological cycle, at least as strong as the effect of human water use (applying irrigation, abstracting water for e.g. industrial use, including reservoirs etc). Globally averaged, changing the land cover from 1850 to that of 2000 increases discharge through reduced evapotranspiration, with large spatial variability in magnitude and sign of change depending on e.g. the specific land cover change and climate zone. In contrast, the inclusion of irrigation, water abstraction and reservoirs reduces global discharge through enhanced evaporation over irrigated areas and reservoirs as well as water consumption. Hence in some areas land cover change and water distribution both reduce discharge, while in other areas the effects may partly cancel out. The relative importance of both types of impacts varies spatially. From this study we conclude that land cover change needs to be considered when studying anthropogenic impacts on water resources.
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