De l'identification des contraintes environnementales à l'évaluation des performances agronomiques dans un système irrigué collectif. Cas de l'oasis de Fatnassa (Nefzaoua, sud tunisien).

摘要

In arid and semi-arid regions, the questions of the performance and the durability of community-managed irrigation schemes are often raised. Disciplinary approaches dealing with these issues are often fragmentary and do not enable neither identifying the effective root causes that hinder community-management of irrigation, nor evaluating their effect on the performances of irrigated systems in such regions. In this context, the present study sought to narrow these gaps by conducting an integrated approach of a comprehensive analysis of constraints and structured assessment of the performances in an oasis located in southern Tunisia. The aim was to help prioritizing intervention in complex systems. A diagnostic analysis according to farmers' perceptions and engineering approach was first conducted. A critical analysis of the farmers' discourses and practices enabled us to identify the principal constraints and their effects, but also to understand their practices of adaptation to the environmental constraints. According to a set of indicators identified following the diagnosis analysis, the evaluations of irrigation management and date palm performances were then performed. The assessment of the performance of irrigation management at community irrigation scheme and field levels highlights that the low frequency of the water delivery turns is related to socio-technical factors due especially to inappropriate practices and a low commitment of some farmers. The analysis of the quantitative and qualitative performances of the date palm highlights the effect of the irrigation operation, and the interaction of salinity and waterlogging constraints. The approach illustrates the complexity of the system and the need for a posture change, of traditional normative and participative approaches, for the implementation of adapted interventions. It is thus a question of including local specificities and social and historical context but also the farmer's action logic to adapt the projected technical changes.