The geography of natural water resources in the Mediterranean basin cannot simply be reduced to the study of water inputs, water distribution, and the pattern of runoff-generating precipitation determined by climate and relief—although these are, of course, fundamental controls (Margat 1992; Benblidia et al. 1996). Any consideration of basin-wide water resources also needs to consider a range of territorially determined factors affecting water resources. These include: (1) the nature of surface and underground flows, which depends on river basin and hydrogeological characteristics; (2) the natural storage capacity of lakes and aquifers and their role in regulating flows, and any losses from these stores which reduce the resulting flows; (3) the existence of favourable conditions for water management and exploitation such as suitable sites for dam construction and the productivity of aquifers, as these factors dictate accessibility to water resources and the production costs; (4) the natural quality of the water, its vulnerability to pollution and its capacity for self-purification; (5) any constraints imposed for reasons of environmental conservation, which may effectively exclude a proportion of water reserves from the category of exploitable resources. It is important to appreciate that each of these factors influences the assessment of water resources in a given area and each factor has its own geography (Margat 1997; Margat and Vallée 1999a). In spite of the broad similarities in climate and landscape between the different parts of the Mediterranean basin, there are considerable variations between regions that impact upon the availability of water resources. Many of the factors affecting water resources cited above are subject to a similar degree of variation (Grenon and Batisse 1989; Chapter 8) and these are discussed in turn below. Marking the transition between the temperate climate of Europe and the aridity of North Africa and the Near East, the Mediterranean climate contains wide variation, and this is reflected in a highly uneven distribution of rainfall (Benblidia et al. 1996; Margat and Vallée 1999a; Chapter 3). For example, moving from one extreme to another, average annual rainfall ranges from more than 3,000 mm in parts of the Dinaric Alps to less than 50 mm in Libya.
Diachasmimorpha longicaudata as Biological Control agent of the Mediterranean fruit fly, Ceratitis capitata: biotic and abiotic factors affecting its implementation in citrus crops of the Mediterranean basin