Evaluation of Chemical Quality of Groundwater Resource in Dharwad District, Karnataka

The chemical quality of groundwater resource of Dharwad district has been evaluated by considering 129 pre-Monsoon water samples collected from dug wells and bore wells. The study area has been divided into the eastern and western parts on the basis of occurrence of black, and red-Loamy-Sandy soils respectively. The total dissolved salts (TDS) vary from 222 to 1624 mg/l in the western part, while it ranges between 310 and 11684 mg/l in the eastern part. While the groundwater of the western part is "potable and suitable for irrigation", it is "brackish and unsuitable for irrigation" in the eastern part, barring few isolated pockets Na-Ca and Cl-SO₄-HCO₃ facies predominates the groundwater of the western part, while Ca-Na and Cl-SO₄ facies predominates the eastern part. The TDS isogram map has disclosed that the black soils and the weathered granitic and gneissic rocks with mafic enclaves may be the causative factors for the increased brackish quality of groundwater of the eastern part. The study has also indicated that the role of base exchange phenomenon and the rock-Water interaction in the weathered zone due to longer residence time of groundwater causing increased brackishness of groundwater in the study area.