Incidence of Brackishness in Ground Water from Bore Wells Drilled in Deeper Aquifers in Parts of Kozhikode District, Kerala, Southern India

Seasonal salinity along river mouths is generally observed in the coastal tracts of Kerala at places. The problem is felt during summer season with the incursion of sea water along river mouths, which imparts brackishness to the adjoining phreatic aquifer systems along the coastal tracts of Kerala. This process is reversible through seasons; during the rainy season, the aquifer freshens up and by summer it becomes brackish. However, the reports of brackish water in bore wells tapping deeper crystalline formations are quite rare in Kerala. This paper discusses the comparison of hydrochemical characteristics of bore wells tapping freshwater to those of having relatively high TDS. Major hydrochemistry of the water samples was studied and in Hill Piper diagram 88% of the samples fall in the field of Ca2+˗ HCO– type facies. The ionic abundance can be expressed as Ca2+>Mg+>Na2+ for cations and for the anions as HCO– >Cl– >SO2– and the EC values range from 82-292μS/cm. The remaining 12 percentage of the samples are found to have relatively high TDS and falls in the field of Na+˗Ca+˗Cl– type and the brackishness of the bore well water could be partly attributed to the inflow of saline water to the deep fractured aquifer systems through lineaments connected to brackish surface water body/sea. Besides, the phreatic aquifers in the area are copiously fresh and EC values are generally below 500μS/cm. Out of the three wells with brackishness, EC values of two wells were found to above 10000μS/cm (Ramanattukara and Kannore) whereas at Paleriitis 1765μS/cm. It is revealed that majority (88%) of the ground water samples are highly suitable for agricultural purposes with all types of soil except those of the Ramanattukara, Kannore and at Paleri exploratory bore well samples. Keywords: Litholog, Hydrogeology, Hydrochemistry, Mixing, Deeper Aquifer, Kozhikode