The main objectives of this study are to evaluate the impact of irrigation water use efficiency improvement on enhancing the value of water used for irrigation; and to estimate the potential for private water cost reductions in irrigated durum wheat production systems of semi-arid Tunisia. Data Envelopment Analysis and stochastic frontier methods were combined for this aim. Results show that significant inefficiencies exist in the farm sample under investigation. We also show that increasing irrigation water use efficiency could shift the curve of marginal water value upwards, thereby indicating a rising of water value. By operating at full water economic efficiency level, farms would be able to reduce water costs for wheat production by about 42%, in average. We conclude that there is a wide scope to improve water use efficiency in the study area, allowing for a better valuation of the water resources used for the irrigation.