The Effects of Overexpoliation and Land Use Change on Groundwater Resources Salinization Using Vulnerability Concept in the Ghaemshahr-Juybar Aquifer

Groundwater vulnerability is due to the inherent vulnerability and characteristics of the occurrence of contaminating sources and human-induced pollution. Sixty four quality measuring wells, 20 observation wells and more than 28000 operating wells were sampled in order to provide vulnerability maps for 2004 and 2014. The essential factors of the inherent vulnerability included hydraulic conductivity, aquifer type, distance from the coast, and aquifer thickness. Additional factors of specific vulnerability including well density, decline of groundwater level, relative impact of seawater intrusion, condition of saltwater up-coning and hydraulic gradient were also used. The results indicated that the quality of groundwater resources had declined from 2004 to 2014 according to salinity criteria such as electrical indicated by an increase in conductivity (EC), sodium absorption ratio (SAR) and total dissolved solids (TDS). The land use factor was also used to prepare modified vulnerability maps for the year through 2004-2014. The results indicated that while the irrigated area had decreased by 8 percent during this period, the level in high-vulnerability areas had increased, which may be surmised that an increase discharge rate and double-cropping had caused degradation of the groundwater. The results showed that the mean correlation coefficient of vulnerability to salinity classes with salinity criteria such as EC, TDS and SAR had improved in 2004 from 0.65 to 0.9, and in 2014 from 0.78 to 0.87. Duo to the complexity of qualitative modeling, solute transport and groundwater salinity, the modified vulnerability maps is a good tool to predict the impending groundwater salinization.