Irrigation water use efficiency in collective irrigated schemes of Tunisia: determinants and potential irrigation cost reduction

This study aims first to measure the farm specific irrigation water use efficiency (IWUE), through non parametric DEA model; and second to evaluate the potential irrigation cost reductions and identify the main factors causing variations in IWUE among the sample farms. Cross sectional data collected from a sample of 75 farms participating in the WaDImena project in Nadhour region (northern Tunisia) was used for this aim. The results showed that the average level of IWUE across the farm sample was around 61.2% under variable returns to scale (VRS) assumption. However, the estimated mean irrigation water technical cost efficiency (ITCE) is much higher than IWUE. Farmers would be able to reduce their actual cost by 5% under VRS by adjusting irrigation water to its efficient level. This low level of cost reductions is consistent with the existing literature about IWUE in Tunisia. Moreover, education level of farmers, access to credit and agricultural extension service showed a positive relationship with the IWUE in our case study.