ABSTRACT
Efficient water use is an essential element in sustainable water use. But it is only part of the full story. The emphasis on efficiency makes us talk about less water use per unit of production. A famous slogan in the ongoing debate about freshwater scarcity is ‘more crop per drop’. Although this sounds good, it makes us forget that, in the end, it is the total water consumption determining the impact on the environment. There is an increasing number of places on Earth where water resources are used in a very efficient way – with good amounts of crop per drop – but where water resources are depleted very quickly at the same time. The total impact of production on freshwater resources depends on two factors: the water use per unit of production and the total production. Everywhere, we can see companies reducing the volume of water consumption per unit of production, but the total volume of production grows often quicker, so that the total water consumption of the company increases. We can also find many catchments in which the water footprint per unit of production decreases, but where total production grows quicker, so that the total water footprint in the catchment effectively becomes bigger. It is thus as important to consider total production of water-intensive commodities as to look at water use per unit of production. In this chapter, we will first examine what practitioners in the water field mean by ‘efficient water use’. The term efficiency is being interpreted in different ways, so it often happens that what can be seen as efficient from one perspective, is not efficient from another perspective. There are three levels at which one can consider the efficiency of water use: the water user level, the river basin level and the global level (Hoekstra and Hung, 2005). In addition, at whatever level wateruse efficiency is examined, there are two different perspectives: the physical and economic perspective. Traditionally, water resources managers – often educated as engineers or hydrologists – think in terms of water volumes allocated to different users, so they take the physical perspective. More recently, we see economists
joining the debate on water scarcity and they emphasize the importance of looking at costs and benefits of water use. After a critical review of the different efficiency concepts, we will move on to a reflection on the limitations of increasing ‘resource efficiency’ and on the so-called ‘rebound effect’.
