Sharing Scarce Resources in a Mediterranean River Basin: Wadi Merguellil in Central Tunisia

Owing to its geographical location, Tunisia is under the influence of a Mediterranean climate in its northern part and a Saharan climate in the southern part. This climatic discontinuity results in a strong variability in water availability and defines three agro-climatic zones: (i) the northern area, with its forestry and agricultural vocation, which includes the Medjerda (the only permanent river) and provides 82% of the country's surface water; (ii) the semi-arid centre, initially a wide rangeland with large plantations, characterized by violent and sporadic runoff; and (iii) the southern area (62% of the country), where settlements are concentrated around water sources (springs, oases) and where people live on extensive pastoralism. Tunisia has many aquifers, storing 720 Mm3 each year in the northern and central areas and 1250 Mm3 in the south of the country (DGRE, 1995).