Management, Operation and Maintenance (MOM) performance is the degree of fulfilment of either a specific quantified output target typified by such thing as yields, water use efficiency and cropping intensification or a specific input target such as discharge, water level or timing of irrigation deliveries. Considering about 1.7 million hectare irrigation areas turned over to Water User Associations in Turkey, shows clearly the importance of the irrigation schemes performance. The purpose of this research was to measure and evaluate the performance of the MOM of Nazilli, Akçay and Aydýn irrigation schemes using the WAM (Weighted Average Mark) method in the Great Menders basin in Turkey in before and after turnover. The measurement and the evaluation of the MOM's performance is done by scoring according to an index system consisting of twenty techno-economic performance indicators. The higher WAM value indicates the best performance. Average WAM values in before and after turnover were (71.14, 78.02), (78.93; 82.23) and (82.60, 83.24) for Akçay, Aydýn and Nazilli irrigation schemes respectively. Performance of irrigation schemes in basin in periods after turnover was found good. WAM values calculated to index the system of MOM in before and after turnover in the basin schemes didn't vary widely. But after the turnover, the WAM value related to MOM's economical and institutional indicators increased in somewhat than before.