Assessing salinity and sodicity hazards of ground water for irrigation purposes using fuzzy logic

In order to perform environmental management, precise classification and identification of groundwater quality is necessary. There are various uncertainties with traditional classification methods. In recent years fuzzy logic-based methods are widely used to control uncertainties in different environmental problems. Therefore, a fuzzy logic approach was developed to evaluate the groundwater quality of Rafsanjan plain in Iran. The plain is known for its intensive pistachio production, which has caused water table draw downs and depletion of groundwater resources. In this study three parts of FAO guideline for irrigation water quality assessment were combined by fuzzy logic to create a new method for assessing salinity and sodicity hazards of irrigation water. Salinity fuzzy inference system (FIS) was constructed with water electrical conductivity (EC) and total dissolved solids as inputs and infiltration; FIS (sodicity hazard) was constructed using sodium adsorption ratio and EC and then, these two FISs (salinity and sodicity) were combined to develop a new FIS that can be used to assess irrigation water quality. The results of the calculated FAO guideline and fuzzy logic approach have yielded good agreement. In order to evaluate models' validation, the available water quality data from 20 wells, from 2002 to 2010 in Rafsanjan plain aquifer were used. Results showed that water quality in this region is bad to medium in the view of salinity and sodicity hazards.