Articles | Volume 21, issue 11
Hydrol. Earth Syst. Sci., 21, 5603–5626, 2017
Hydrol. Earth Syst. Sci., 21, 5603–5626, 2017

Research article 14 Nov 2017

Research article | 14 Nov 2017

Hydrological impacts of global land cover change and human water use

Joyce H. C. Bosmans1, Ludovicus P. H. van Beek1, Edwin H. Sutanudjaja1, and Marc F. P. Bierkens1,2 Joyce H. C. Bosmans et al.
  • 1Department of Physical Geography, Faculty of Geoscience, Utrecht University, Utrecht, the Netherlands
  • 2Unit Soil and Groundwater Systems, Deltares, Utrecht, the Netherlands

Abstract. 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 PCR-GLOBWB, a combined global hydrological and water resources model, to assess the impacts of land cover change as well as human water use globally in different climatic zones. Our results show that land cover change has a strong effect on the global hydrological cycle, on the same order of magnitude as the effect of human water use (applying irrigation, abstracting water, for industrial use for example, including reservoirs, etc.). When globally averaged, changing the land cover from that of 1850 to that of 2000 increases discharge through reduced evapotranspiration. The effect of land cover change shows large spatial variability in magnitude and sign of change depending on, for example, the specific land cover change and climate zone. Overall, land cover effects on evapotranspiration are largest for the transition of tall natural vegetation to crops in energy-limited equatorial and warm temperate regions. In contrast, the inclusion of irrigation, water abstraction and reservoirs reduces global discharge through enhanced evaporation over irrigated areas and reservoirs as well as through 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 across climatic zones. From this study we conclude that land cover change needs to be considered when studying anthropogenic impacts on water resources.

Short summary
We investigate how changes in land cover, such as deforestation, affect river runoff and evaporation from the land surface. We use computer simulations to show that the impact of land cover changes is significant and, when globally averaged, it is as important as more direct human impacts through water use (such as irrigation). There is large spatial variability in the impact of land cover change, with the largest changes when tall vegetation (such as forests) is replaced by crop fields.