Evaluation of Irrigation Water Quality Using GIS-based Analytic Hierarchy Process (AHP) in Kızılırmak Delta (Turkey)

The Kızılırmak Delta is the largest wetland in Turkey. In the delta, sea, river, lake, dune, reed, swamp, forest and agricultural areas coexist in a common ecosystem and it was declared as Ramsar area in 1998. Chemical pesticides and fertilizers used in conventional agricultural activities are left to wetlands through irrigation drainage channels. Also, seawater intrusion is a negative effect on water resources. In present study, GIS-based analytic hierarchy process (AHP) method was used to evaluate the irrigation water quality in the drainage channels. There are four main parameters that control the irrigation water quality. These are defined in the literature as leaching and permeability hazard (IPH), salinity hazard (SH), miscellaneous effect on sensitive products (ME) and specific ion toxicity (SIT). In the evaluation of these parameters in this study, nine different criteria such as EC, Total dissolved solids (TDS), SAR and EC, Na/SAR, Cl, B, NO 3 , HCO 3 and pH were taken into account. Irrigation Water Quality Index (IWQI) was calculated using weight coefficients of each criterion and also total weights determined based on ion concentration of the waters. According to obtained results, IWQI varies from 0.2337 to 0.6017 in June and varies from 0.0784 to 0.6017 in October. The low, medium and high suitability classes were defined for normalized IWQI values. The IWQ index maps of drainage channels show that most of channel waters in Kızılırmak Delta are medium and/or low suitable for irrigation purposes. In the delta, KD-1 has high suitability, KD-6 and KD-7 have medium suitability, KD-2, KD-3, KD-4, KD-5, KD-8, KD-9 and KD-10 have low suitability for irrigation water in the starts of the irrigation season, KD-7 has high suitability, KD-1, KD-2 and KD-8 have medium suitability, KD-3, KD-4, KD-5, KD-6, KD-9 and KD-10 have low suitability for irrigation in the ends of the irrigation season. This situation indicates that the irrigation water to be used for agricultural activities in the region is limited and it is possible to encounter serious problems for the future. For this reason, it is necessary to take necessary urgent measures by reviewing the agricultural policies and water management in the delta.