Humans’ role in droughts across the world

"Very few scientists take the human factor into account"

Global warming strongly affects water tables and river-water levels and can cause long periods of drought. Human activity can significantly affect this process, either positively or negatively, concludes PhD candidate Niko Wanders in two recent publications in scientific journals. It is important, therefore, to include human influence as a decisive factor in predicting world-wide droughts. 

Folsom Lake
Folsom Lake (California) during a long period of drought

In large parts of the world, including the Horn of Africa, droughts can last for years, with a huge impact on society. Droughts mean not only a reduction in the quantity of drinking water, but also a lower electricity and food production, and an increased risk of forest fires and higher greenhouse-gas emissions.

Human factor

Droughts are partly attributable to global warming, but also to humans, according to PhD candidate Niko Wanders’ publications. ‘We simulated on a global scale what is happening to groundwater and rivers when global temperatures rise. And we compared our modelling results with data for the last thirty years of the previous century. What is special about our models is that they can take human factors into account. We are one of the few universities that can do this,’ Wanders proudly explains. 

Niko Wanders

Human impact is different everywhere

Wanders’ conclusion from these modelling results is that the roles that humans play in increasing drought conditions all over the world are significant, albeit very diverse in different places. As he explains, ‘Poor irrigation practices and the naturally low availability of water in the Middle East are major contributing factors to local drought conditions. Conversely, more knowledge and more advanced technology in the Western world make a positive contribution to water tables by retaining water in wet winters. We can learn a lot from each other.’

Substantial difference

‘Although the human impact on water tables and river discharges varies greatly in different parts of the world, from negative to positive, it definitely plays a significant role,’ continues Wanders. Humans have more impact on the available amount of water than we had previously assumed. So it is important to include human influence in predictive hydrological models, and unfortunately no or too little account is currently being taken of this factor.’


Wanders, N. and Wada, Y. ‘Human and climate impacts on the 21st century hydrological drought’, J. Hydrol. (2014),

Wanders, N., Wada, Y. and Van Lanen, H.A.J., ‘Global hydrological droughts in the 21st century under a changing hydrological regime’, Earth Syst. Dynam., 6, 1-15,

More information

Tom de Kievith MA, Press Officer, Faculty of Geosciences, Utrecht University, 0031 (0)30 253 5593,

Faculty of Geosciences: a sustainable Earth for future generations