Water scarcity indicators; the deception of the numbers

The water scarcity indicators that are presently used to indicate the level of water shortage in the different parts of the world suffer from serious flaws. First of all, they are limited to "blue" water only, neglecting the important contribution that "green" water makes to global food production. Secondly, they are based on averages and hence hide the very important temporal and spatial variations of the water resources, which are often the determining factors for water scarcity. Subsequently, they do not consider climatic differences, differences between primary and secondary uses, or the effect of life-styles. A contentious issue is how to distribute the water resources over the different countries sharing a river. The way in which it is done is not at all clear and will require an objective key for allocation among riparians. A new approach is needed to develop indicators that take these aspects into account (C) 2000 Elsevier Science Ltd. All rights reserved.