Hydrochemical Facies, Groundwater Pattern in 'Red Beds and Basaltic Aquifers', Origin of Brackish Waters And Salt Encrustation, Khanapur Plateau, Western Ghats, Maharashtra, India

An integrated Hydrochemical, geochemistry and mineralogy of the salts encrustation on the 'red beds' on the Khanapur plateau, along the eastern side of the Western Ghats (Hills) of India region of the Indian peninsula. This area receives low precipitation (638 mm/year) as compared to the western side (4000 to 6000mm/year). Over a greater of the Deccan Volcanic Province of India, the basaltic aquifers contain fresh water with TDS<1000ppm. However, brackish waters (TDS>1000ppm and <10.000ppm) have been recorded in the alluviated aquifers in the region. The present study deals for the first time with an occurrence of brackish waters in the 'red beds' area on the Khanapur Plateau. The data collected for groundwater samples and salt encrustation, suggesting the origin of salinity imposed to the groundwater system in the area. It is evident that the waters are saline during the pre-monsoon period. The semi-arid climate conditions prevailing in the area during the Quaternary period and chemistry and mineralogy of the 'red beds', might have played an important role in imparting salinity to both soil and groundwaters. There are significant variations in the chemistry/quality of groundwaters in different seasons and aquifers. The groundwaters show changes in their chemical characteristics during monsoon season and waters from the shallow basaltic and 'red beds' aquifers exhibit shift in their Hydrochemical facies from Cl+SO4, HCO3 to HCO3, Cl+SO4 . The post-monsoon season shows the dominance of groundwaters with Cl+SO4, HCO3 anion Hydrochemical facies with shift in the cation Hydrochemical facies from Na+K, Ca+Mg to Ca+Mg, Na+K. The calculated SAR values indicated that the water is saline and do not suitable for irrigation. The salt samples subjected to chemical and mineralogical analysis to understand their origin and genesis. IR data shows the dominant of the carbonate minerals as, magnesite, calcite and dolomite associated with clay as montmorillonite, illite, huntite, kaolinite, nontronite and other iron oxides; hematite, siderite, , goethite, with quartz and gypsum.