Resistivity Investigations for Ground Water in Metamorphic Areas Near Dhanbad, India
Dr. R. K. Verma graduated with the Ph.D. degree from Harvard University, U.S.A. in 1959. He worked in the Oil and Natural Gas Commission (1959-61) and National Geophysical Research Institute, Hyderabad (1961-69), before joining as Professor in the Department of Applied Geophysics the Indian School of Mines, Dhanbad. He has carried out research in several fields of investigation including elasticity of rocks, paleomagnetism, heat flow, gravity surveys as well as ground-water investigations.
Dr. M. K. Rao obtained his M.Sc. degree in Geophysics from Andhra University, Waltair in 1951. He joined the Department of Applied Geology, Indian School of Mines in 1956. In 1963 he transferred to the Department of Applied Geophysics in the same School. He obtained his Ph.D. degree from the University of Ranchi in 1967. His fields of research include magnetic exploration and use of electrical methods for ground-water exploration.
Mr. C. V. Rao obtained his B.Sc. in Physics in 1974 and M.Sc. (Tech) degree in Geophysics from Andhra University, Waltair in 1977. Since then he has been working as a research scholar in the Department of Applied Geophysics, Indian School of Mines, Dhanbad. Currently he is working for his Ph.D. degree in the field of electrical resistivity methods pertaining to ground-water exploration.
Despite sufficient rainfall, large parts of Eastern India suffer from water scarcity. Ground water occurs in weathered or semiweathered/fractured layers in hard-rock areas whose thickness varies, in general, from 5 to 20 m.
Ground-water studies have been carried out in several areas in and around Dhanbad (Lat. 23°48′N, Long. 86°24′E) in Bihar State of India. The area covers Pre-Cambrian hornblende and feldspathic gneisses, schists, granulites, quartzites, metabasics and pegmatities. The area forms a part of ENE-WSW trending Satpura orogenic belt. The quartz reefs formed as fault fillings act as barriers to the flow of ground water. Geophysical investigations, using electrical methods, with Schlumberger configuration using AB up to 300 m were carried out at most of the locations. Conventional resistivity meters were used for this purpose.
The data from 78 Schlumberger soundings has been analysed. Both A and H type curves were obtained. Spectrum of resistivity values has been prepared to study the over-all variation of resistivity values in the area. It is observed that the curves with arithmetic mean values are quite representative. The values obtained from spectral and regression analyses are nearly the same.
The results of geoelectric soundings have been compared with the geological section wherever available. It is inferred that the thickness of the weathered layer as deduced from Schlumberger soundings includes partly the unweathered/fractured layer as well. An attempt has been made to find an empirical relationship between the daily yield of water in gallons/day and the longitudinal conductance (s = h/p) of the weathered layer. Two empirical relationships have been obtained, one for the winter months, December-January and the other for the summer months, June-July. A suitable explanation for the two curves has been given.