Les Ziban : durabilité des effets des aménagements hydrauliques et atténuation des risques d’inondation et de sècheresse.

Abstract

The Ziban, located in the extreme North-east of the Sahara in an arid climate (rainfall below 150 mm/year), benefit from the waters of the Septentrional Sahara Aquifer System (SASS) and surface run-off from the southern flank of the Saharan Atlas (Oued Labiod, Abdi, El-Hai, Larab and Oued Djedi). This situation provides them with significant and diversified water resources (groundwater and surface water), which have given rise to a number of Oases that have shown unrivalled agricultural dynamism in recent decades. Today, however, surface water only accounts for 7 % (82 Hm3 /year) of mobilized water resources. Nevertheless, their inflow has ensured the recharging of aquifers, particularly groundwater tables, which has supplied and continues to supply the city of Biskra with drinking water. Groundwater resources account for 98 % (1124, 24 Hm3/year) of mobilized water resources. Today, the rate of abstraction imposed by the expansion of developed areas (1040 ha/year) has led to a significant reduction in water levels and a deterioration in the quality of the resource. In this context, the impact of man’s action can aggravate the imbalance or mitigate the contradictions and promote the resilience of a rapidly developing region. In addition, the Foum El Gherza dam, 80 % silted up, no longer ensures flood control, hence the reappearance, after decades, of the risk of flooding in its downstream section (towns and agriculture). However, the impoundment of the fountain of the Gazelles and Bouzina dams (2000 and 2021) has dried up the Oueds El-Hai and Abdi, which were responsible for recharging the groundwater downstream. However, the planned underground dam (Ouled Djellal) remains the most suitable for hydro-morphological conditions and is perfectly suited to the harsh conditions of arid zones. To support the current pace of development, it has become inevitable to connect the Ziban to other regional sources. To this end, two water transfer projects have been adopted, a supply from the Albien at Touggourt and a drinking water supply from the Beni Haroun transfer system (Koudiet Medaouar dam). This strategy can only guarantee the resilience of the Ziban region.