Wasser - Elementare und strategische Ressource des 21. Jahrhunderts : III. Eine Bestandsaufnahme

Abstract

Background and aim The combination of increasing freshwater demand, limited or regionally decreasing water resources as a consequence of the climate change, and an increasing qualitative burden, lead more and more to the question as to whether the population of particular regions, whole continents or even the entire world will be confronted with a shortage of available water resources in the future. Discussion The resident-specific regenerative water resources of the continents are being quantitatively rated on the basis of an analysis of the three globally relevant water cycles (the marine one, the terrestrial one and the one which is linking both of them). The available amount of water is limited by technical-economical restrictions. This amount is compared with human demands, and the outstanding relevance of the production of biomass (to be used as food, animal feed, primary product or energy carrier) regarding the worldwide water need is discussed. Results From a global point of view there is no water shortage. Scarcities occur only regionally or seasonally. A large portion of the water employed worldwide is used for the production of biomass. Therefore, this sector provides a considerable key to the strategic handling of water. The so-called 'green water' is crucial for the production of biomass. However, the common way of balancing water supply and demand often overlooks the importance of the green water on the supply side and thus indicates shortages which de facto do not exist. As to the whole usage of water by humans, in our opinion, the stated quantity of freshwater which is being regenerated every year all over the world has to be corrected considerably. The figure of 40,000∈km3 which is often quoted in current literature has to be raised to more than 100,000∈km3. Conclusions and perspectives Water shortage is often not a result of limited resources or technologies but is a consequence of missing awareness, failing political volition or insufficient socio-economic potentials. On the basis of a comprehensive water supply/demand balance, which includes all forms of water usage, national and international potentials for the fulfilment of the demand should be analysed in order to be able to develop necessary supply scenarios. © 2009 Springer-Verlag.