Identifying major factors affecting groundwater quality of the Galehdar plain, south of Fars province

Nowadays, the quality of water resource and recognition of the effective factors in it is one of the most important issues in the world regarding consideration of water shortage. The interaction between water resources and porous and environmental media plays the important role to control of groundwater quality. Moreover, identification of this interaction can be helpful for optimal water management. Because of its agricultural and industrial importance, the groundwater quality assessment of these interaction affects the Galehdar plain which is located in the south of Fars province, Iran, is necessary. In this study, geological and anthropogenic factors affecting the groundwater quality of Galedar plain were investigated using analyses and interpretation of pumping-well quality data of 20 water well samples in March 2011. Piper charts, composition diagrams, statistical analyses, factor analysis, saturation indices, and maps of the hydrogeochemical parameters were used to in determination of the salinity sources and effective processes affecting the quality water of the aquifer. Water type changes from carbonate and sulfate to sodium-magnesium chloride in the direction of groundwater flow which is being consistence with Chebotarev ionic evolution and higher residence time. Based on piper diagram, groundwater of Galehdar is Cl-Na and SO4-Ca type. The composition diagrams show a clear linear trend between Na and Cl and also between Ca and SO4. This implied the arrival of waters originating from halite and gypsiferous formations and salty soils. Statistical and factor analyses demonstrate three effective groundwater quality-control factors. The first factor which is the most effective groundwater quality control-factor, explaining 51.9 percent variance of data and shows halite dissolution. Assessment of saturation indices demonstrates that total trend of hydrogeochemical processes of Galehdar plain is halite and gypsum dissolution and sedimentation of calcite and dolomite. Surface waters recharging the aquifer where passed through the unsaturated aquifer media is the most probable of deterioration of water quality and chloride ion concentration increasing. The results show that the main groundwater quality degradation reasons are waters passes over salty soils, agricultural wastewaters, salt-water rivers, dissolution of gypsum and halite, and runoff originating from Gachsaran and Aghajari formations which is the most effective factor in the Calendar groundwater quality deterioration.