Determination of Adequacy and Equity of Water Delivery in Irrigation Systems: A Case Study of the Gediz Basin

This study assesses the water delivery performance of four selected Water User Associations (WUAs) in the Gediz Basin irrigation system from the point of view of adequacy and equity for the years 2004 and 2005, using remote sensing techniques. Adequacy of water delivery was determined according to Irrigation Ratio (IR), Water Use Ratio (WUR) and average of Normalized Difference Vegetation Index (NDVI sub(ave))and equity according to values of the coefficient of variation of NDVI (CV sub(ndvi)). IR values for the WUAs varied between 48 and 89% each year, averaging 77% in 2004 and 76% in 2005. WUR values for the selected WUAs varied from month to month each year, with seasonal average values close to or greater than 1. NDVI sub(ave) values for all WUAs were higher in 2004 (0.32 as against 0.42). CV sub(NDVI) values for 2004 varied between 0.14 and 0.23 and for 2005 between 0.14 and 0.30. The IR indicator showed that a WUA located at the end of a main canal which served more than one WUA did not receive adequate water. The WUR indicator showed that while the amounts of water supplied during the season to the selected WUAs were close to the amounts planned, in both seasons water was not supplied homogeneously month by month. The NDVI sub(ave) indicator showed that the selected WUAs were more successful in supplying water adequately in 2004. Finally, the CV sub(NDVI) indicator showed that the selected WUAs were parallel in terms of equity in both years; that is, it showed that a given WUA showed the similar success level each year.