Modélisation stochastique de l'usage agricole de l'eau et développement durable autour des lacs collinaires en Tunisie centrale : Application à la retenue de Djebel Hallouf dans le Gouvernorat de Kairouan

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This research work attempts to determine and to analyse the behaviors of the farmers in term of adaptation and viabilily of production systems to the dubious and limited availability of water in small dams. For that, an analysis of the case of the Djebel Hallouf reservoir, located in the district of Kairouan with a storing capacity of 95 000 m³ was used. The practical method followed in work consists of three essential stages : (i) initialy, a typology allowed the identification of the various production systems undertaken by farmers. The various types of exploitation around the reservoir were then modeled using the stochastic programming; (ii) in the second time, results of the basic models and their sensitivities to annuaI variations of irrigation water, were analyzed. The water demand functions of the various farms are set up and analyzed: (iii) in a third phase, and in order to analysis the technical and economic functioning of water reservoirs with regard to the problem of situation which affects its capacity in the time, dynamic model have integrated the factor time and have been useful to analysis the production systems evolution and their subsequent incomes. In general, the randomness of the filling of the reservoirs is the origin of the instability of the annual farmers incomes. The water demand functions of various farms are rigid owing to the fact that the cost of water represents a weak shore of the gross margin of crops. Production systems based on annual crops were not viable given the siltation process, which affects directly the through time water supply. The practice of these later comes in contradiction with the logic of sustainable development which governs the sectorial policy of the government in matter of hill reservoirs construction. Thus, the practice of tree plantation comes as a viable alternative able to generate through time relatively steady incomes and to induce consequently a sustainable local agricultural development around hill reservoirs.