ABSTRACT
This study was carried out to investigate the impact of drainage basin’s lithostratigraphy on the quality and type of stored water in the Mujib dam reservoir. The water samples were collected on a monthly basis from surface water from January 2012 to December 2015. The classifications of collecting water samples for domestic and irrigation purposes were based on different physico- chemical parameters such as pH, EC, TDS, TSS, Na+, K+, Ca2+, Mg2+, Cl-, SO42-, HCO3- , NH4+, NO3- , NO2- , SAR, RSC, SSP, RSBC, PI, MAR, KR, and TH. All analyzed water samples were satisfied the Jordanian permissible limit and graded as “fresh water”. The hydrochemical indices (Mg/Ca and Cl/HCO3) and Cation Exchange values (CEV), indicating that the surface water chemistry is due to the rock weathering minerals with respect to their inland origin. The water samples have complied within the respective limits in respect of pH, EC, SAR, RSC, RSBC, MAR, KR, SSP and PI, and hard in respect of TH which may be due to the dissolution of the weathered rocks. Abundance of cations and anions is in the following order: Ca > Na > Mg > K and HCO3 > SO4 > Cl > NO3 during the period 2013-2015 and SO4 > HCO3 > Cl > NO3 through 2012. Thus, calcium and bicarbonate–sulfate are the dominant ions present in the surface water of this study. Piper diagram suggested that carbonate and gypsum weathering is the dominant process controlling reservoir water chemistry in the basin area. The quality and type of surface water can be modified by the lithology of the catchment area. The hydrogeochemical study of Mujib reservoir water indicated that the water quality is safe for drinking and agricultural purposes.