Assessment of groundwater quality index (GQI) for Lenjanat aquifer using GIS

This paper has evaluated the groundwater quality index of Lenjanat aquifer. Water quality index as a unique index is presented to describe overall water quality conditions using multiple water quality variables. Physical and chemical data of 66 water samples were used in this study. The results have been obtained by Comparing the qualitative features with the World Health Organization (WHO) standard and Industrial Research of Iran (ISIRI) standards. In calculating GQI، 7 parameters، including calcium (Ca)، magnesium (Mg)، sodium (Na)، chlorine (Cl)، sulfate (SO4)، total dissolved solids (TDS) and nitrate (NO3) have been used. Groundwater quality index shows the medium to relatively high groundwater quality in the study area. Minimum and maximum value of the index is calculated as respectively 55 and 93. Land use map shows that along the Zayanderood River and around the location of rice paddies، water quality reaches to the lowest quantity. Optimum index factor technique allows the selection of the best combination of parameters dictating the variability of groundwater quality.