The performance of irrigation systems is often challenged. Our research approach was initiated by the following statement: disciplinary approaches treating the specific performance of irrigation systems simplify their complexity. Thus, interventions based only on the hydraulic or the economic dimensions are not the most suitable. So, it is necessary to use a holistic approach to assess the performance of irrigation systems, as is the overall goal of our research. Our approach includes three main steps. The first step is to understand the hydraulic aspects of the irrigation scheme in order to identify its causes of dysfunctions. The second step proceeds to two types of assessments: the first one deal with in situ hydraulic measurements which allowed identifying the most pertinent hydraulic indicator; the second one deal with the analysis of the techno economic data in order to evaluate the economic efficiency. These two steps are a gateway to the third step, in which viewpoints of the hydraulic engineer and the economist identified key levers for better performance and then propose some scenarios and justify their validity. The studied irrigation scheme is localized on the Medjerda river in northern Tunisia.