GROUND WATER CHARACTERISATION STUDIES IN PARTS OF KOLAR DISTRICT, KARNATAKA

Abstract

Groundwater exploration in hard rocks is always a challenge to those who are engaged in this job. By far, no single technique, be it geological, geophysical, has been able to provide an ever successful solution for groundwater exploration in hard rocks. Instead an integrated approach comprising of hydrogeological, remote sensing methods coupled with geophysical methods is useful. In the present study, IRS-imageries of parts of Kolar District, Karnataka have been used for interpreting geological, hydrogeomorphological features that are present in the study area. These features have been transposed on to the drainage map to understand how the master drainage influences the recharge to the study area regionally. The available apparent resistivity data of the vertical electrical soundings recorded in the study area has been discretized and interpreted by using Zohdy's package. The geological interpretation of the resistivity data has helped in assigning resistivity ranges for weathered and fractured granite in the area. Using these ranges of resistivity values, the thickness of weathered granites was assigned at different VES locations and correlated with the bore well lithologs and discharges. However, the method had a severe limitations for identification of saturated fractures in the bed rock. The above comparative study has revealed that the geoelectrical parameters apparently do not have a direct bearing on the availability of groundwater from the fractured bed rock and the identification of saturated fractures and fissures in the relatively unweathered bed rock cannot be made by simple interpretation of resistivity data. In this study, the empirical curve break method was tried to identify the saturated fractures in the bed rock. Attempts have been made to discuss the possible theoretical background of curve break method which was found to be quite successful in the present area.