Water Scarcity Concepts

Abstract

A range of concepts relative to water scarcity are discussed in this chapter. Natural scarcity resulting from arid and semi-arid climates and drought is one issue, and a second is man-made scarcity which is associated with desertification and water shortage due to poor management. Separation of these two causes brings into focus the effects of both water quality and water quantity on water scarcity. An introductory discussion of the respective water management issues and implications for sustainable development are consequently presented. 2.1 Concepts 2.1.1 Introduction At the beginning of the XXI century, the sustainable use of water is not only a priority question for water scarce regions and for agriculture in particular, but for all sectors and regions. Imbalances between availability and demand, degradation of surface and groundwater quality, inter-sectoral competition, interregional and international conflicts, all bring water issues to the foreground. Decades ago, water was viewed as a non-limited natural resource because it was renewed every year in the course of the seasons. Man progressively appropriated this resource and used it with few restrictions. Developments in controlling and diverting surface waters, exploring groundwater, and in using the resources for a variety of purposes have been undertaken without sufficient care being given to conserving the natural resource, avoiding wastes and misuse, and preserving the quality of the resource. Thus, nowadays, water is becoming scarce not only in arid and drought prone areas, but also in regions where rainfall is relatively abundant. Scarcity is now viewed under the perspective of the quantities available for economic and social uses, as well as in relation to water requirements for natural and man-made ecosystems. The concept of scarcity also embraces the quality of water because degraded water resources are unavailable or at best only marginally available for use in human and natural systems. Figure 2.1 illustrates the causes for water scarcity, which may be natural, dominated by climate features, or man-made. Pollution and contamination degrade the L.S. Pereira et al., Coping with Water Scarcity,