Occurrence and quality characterisation of groundwater in hard rock terrains of Karnataka

S. C. Puranik

Department of Studies in Geology, Karnataka University, Dharwad – 580 007, India. E-mail: puranik_sc@yahoo.co.in.

 Accepted 11 December, 2009

   Abstract

Hydrosphere is the term used to define all water bearing units of the earth. It is difficult to understand the occurrence and movement of water within subsurface. The physical and chemical characters of water vary within all the components of hydrologic cycle. Rainwater gets contaminated due to atmospheric pollution. Depending on soil characters the in filtering rain water gets contaminated. Aquifer is the term used to the litho units or set of litho units that store water within the available openings and yield water whenever recovered through wells. Openings are due to structural disturbance in case of consolidated formations in the form of fractures, cracks, joints and faults. They are due to the space between grains in case of unconsolidated and semi consolidated rocks. The alteration of rocks gives an opportunity to minerals to interact with the water that is available within subsurface. The contact time between groundwater and altered minerals in aquifers control the limit of dissolved solids in groundwater. This process of leaching of minerals into water changes the chemical characters of groundwater. The mineralogical characters of rocks and their intensity of weathering control the characters of the water. In the present article the characters of groundwater in rocks viz; granitic rocks, basaltic rocks, schistose rocks, sandstones, limestones, quartzites and laterites are discussed. The groundwater characters related to the aquifers close to sea coast and change of groundwater quality with respect to hydraulic gradient are discussed. Further, the impact of conjunctive use of surface and groundwater, dilution of groundwater by infiltration of rainwater and groundwater quality deterioration due to agricultural practice are also discussed. Human activities also played major role in changing groundwater quality.

Key words: Occurrence of groundwater, quality characters of groundwater, groundwater in hard rocks.