Using satellite remote sensing to assess irrigation performance in Water User Associations in the Lower Gediz Basin, Turkey

The aim of this research was to assess the irrigation performance of the Salihli Right Bank, Salihli Left Bank, Ahmetli, Gokkaya, Turgutlu, Mesir, Sarikiz, Gediz, Menemen Right Bank and Menemen Left Bank Water User Associations (WUAs) in the Lower Gediz Basin in western Turkey, using remote sensing techniques. To reach this aim the performance of the irrigation system for the 2004 irrigation season was determined according to five indicators, namely overall consumed ratio (e_p), relative water supply (RWS), depleted fraction (DF), crop water deficit (CWD) and relative evapotranspiration (RET). Potential and actual evapotranspiration parameters used in determining these indicators were estimated according to the Surface Energy Balance Algorithm for Land (SEBAL) method using NOAA-16 satellite images.Seasonal averages of these indicators ranged from 0.59 to 2.26 for e_p, 0.47-1.66 for RWS, 0.43-1.31 for DF, 180.5-269.5 mm month⁻¹ for CWD, and 0.61-0.74 for RET. According to the seasonal average values of all the performance indicators, the irrigation performance of all WUAs was usually poor. The performance indicators showed that less irrigation water was supplied to WUAs than was needed. It was concluded that proximity to the source could be an advantage in obtaining water, and that when water was insufficient, groundwater in the crop root area could be used.