Green water scarcity and the potential of green water for reducing agricultural blue water consumption


PhD research


Green water scarcity and the potential of green water for reducing agricultural blue water consumption

Persons involved

Joep Schyns, MSc (PhD candidate)

Prof. dr. ir. Arjen Y. Hoekstra (promoter)

Dr. ir. M.J. Booij (daily supervisor)





Agricultural water consumption is dominated by ‘green water’ (soil moisture directly returning to the atmosphere as evaporation) as opposed to ‘blue water’ (surface- and groundwater). Though, research and debate on freshwater scarcity always focus on blue water, because there is a clearly expressed ‘demand’ and blue water can be ‘supplied’. Since there is also an implicit demand for green water, which sustains agriculture and forestry, and its availability is limited, green water is scarce as well.

This research aims to contribute to the scientific understanding of green water scarcity by exploring and applying new comprehensive definitions of green water availability, consumption and scarcity and assessing these variables on a global scale at high spatial and temporal resolution for the present situation and future scenarios, with an initial case study for China. Furthermore, the study will quantify to which extent increased production from rain-fed lands can reduce demand for blue water resources.

A major part of the study is to model the water use of crops with AquaCrop for the entire world, at 5 arc minute spatial resolution, inter-annually.


Dit is de eerste studie die mondiaal de schaarste aan ‘groen water’ in kaart gaat brengen. Groen water is bodemvocht afkomstig van neerslag, de belangrijkste bron van water in de landbouw. Toch gaat alle aandacht altijd uit naar schaarste aan ‘blauw water’, irrigatiewater dat wordt onttrokken aan grond- of oppervlaktewater. Op veel plaatsen wordt meer blauw water gebruikt dan duurzaam beschikbaar. Deze studie bekijkt daarom de potentie om door middel van productief gebruik van groen water het irrigatiewatergebruik te verminderen. Echter, ook groen water is beperkt beschikbaar. Veranderingen in de beschikbaarheid en schaarste van groen water worden geschat voor een aantal toekomstscenario’s.