This paper analyzes the efficiency of Water User Associations (WUA) in the Zeuss-Koutine region (Tunisia) and studies its main determinants. First, Data Envelopment Analysis (DEA) is used to assess the overall WUA efficiency and to evaluate the management and engineering sub-vector efficiencies separately through a mathematical modification of the initial DEA model. In a second step critical determinants of sub-vector efficiency are determined using a Tobit model. A major finding of the study is that WUAs are clearly inefficient. Under variable returns to scale (VRS) speccation, the average technical efficiency of WUA was 84.4%. This implies that output level could be produced by saving 15.6% of (all) used inputs. The average scale efficiency was around 96.5%, indicating that many WUAs are not operating at an efficient scale. Results show also that inefficiencies of the management and maintenance are higher than the overall inefficiency. The average management efficiency is around 80.6% while the average engineering efficiency is 82.3% indicating that about 19% of management and maintenance expenditures could be saved if WUAs were operated in a sound manner. The inefficiency found can be mainly attributed to the number of water pumping stations managed and the number of years of experience operating a WUA (age).
