Hydrologie, sédimentologie et géochimie de l'Oued Tnja (Tunisie septentrionale)

Abstract

The wadi Tinja connects the garaet Ichkeul to the lagoon of Bizerte which is connected to the Mediterranean Sea by a long gullet. The water of this wadi is depending at the same time on the seasonal contributions of marine and fresh waters and has very fluctuating salinities. The important hydrographical network associated with the Ichkeul stretch of water (which the pouring pool surface equals to 2080 km2) are subject to many hydraulic installations, in particular the construction of barriers of fresh water reserves. These latter are likely to disturb the hydrological, sedimentological and geochemical characteristics of the lagoon - lake system (lagoon of Bizerte and garaet Ichkeul) and consequently to damage its diversity and its biological richness. Tinja wadi, which is the garaet Ichkeul outlet represents the principal source of liquid contributions (418 106 m3), solids (28 103 tons) and in nutritive elements (74, 954, 92 and 69 tons respectively of nitrite, nitrates, ammonium and phosphate) to the lagoon of Bizerte. The latter, receives concentrations in heavy metals from the surface sediments of Tinja wadi, which are likely to cause more or less important disturbances, harmful and irreversible on the fauna and the watery flora of this stretch of water, and consequently on the whole of the ecological balance.