Introducing a novel method in evaluation of groundwater hydrochemical characteristics, GWQISI index: case study—Malekan Aquifer, Northwest of Iran

Abstract

The spatial variation of the groundwater salinity, in present study, has been evaluated in Malekan plain aquifer, East Azerbaijan, Iran, proposing a novel method, named Groundwater Quality Index of Saltwater Intrusion (GWQISI). It has been digitally integrated of total dissolved solids (TDS), Cl−/anions, Cl−/(HCO3− + CO32−), Na+/(Na+ + Cl−), and Ca2+/(HCO3− + SO42−) ratios. Each mentioned parameter is utilized to make a thematic layer in aquifer domain. The GWQISI map indicates six classes, ranging from uninfluenced to extermly influenced classes. Based on the results, about 1.75, 4.25, and 62.4 km2 of Malekan aquifer are extermly, highly, and moderately influenced by salinity, respectively. The slighthly influenced zone covers an area of 88.6 km2 and the very slighthly influenced zone covers an area of 385 km2 (74.75% of the total study area). The saturation index, calculated through geochemical modeling, indicates a suitable chemical environment for halite and sylvite dissolutions; weathering and evaporation phenomena were found to be the dominant processes in the ion concentration of the water samples in the study area, upon to Van Wirdum and Gibbs’s diagrams. The results reveal that the northwest section of the study area is the most affected zone by salinity.