Performance of water delivery system at tertiary canal level: a case study of the Menemen Left Bank Irrigation System, Gediz Basin, Turkey

This study examines water delivery performance of the Menemen Left Bank Irrigation System, which is the lower section of the Lower Gediz irrigation system, in the west of Turkey. Performance was evaluated at tertiary canal level, using the adequacy, efficiency, dependability and equity indicators. These indicators were calculated for the nine tertiaries for the 6-month irrigation seasons of 1999 and 2000, using measured water deliveries and calculated crop water requirements. The tertiaries were located in the head, middle and tail sections of the system. Electronic limnigraphs especially installed for this study at the head of each tertiary canal were used to measure discharge during each season. Water delivery performance to the tertiaries in each irrigation season rated worse for adequacy, dependability and equity than for efficiency. The analysis results of the spatial and temporal dimensions of these indicators show that factors causing this problem derive in part from physical structure, and in part from management. Key among these are inadequate water measurement and control at the head of the tertiary canals, tertiary canal capacity limitations, non-compliance with the rotation plan, and mismatch between the reservoir release plan and irrigation demand.