Geo-electrical resistivity and groundwater flow modells for characterization of a hardrock aquifer system

K’Orowe, M.O.^*1, Nyadawa, M.O.¹, Singh, V.S.² Rangarajan, R²

¹Jomo Kenyatta University of Agriculture and Technology, P.O Box 62000, Nairobi, Kenya

²National Geophysical Research Institute, Uppal Road, Hyderabad 500-007, India

*Corresponding author Email: modondi@yahoo.com

Accepted 16 October 2012

Abstract

In the present study, focus is on evaluation of the utilization of geo-electrically derived hydraulic parameters and processes in groundwater flow modelling. Aquifer parameters and processes data, namely, formation factor, transmissivity and natural recharge at some locations are correlated linearly with geo-electrical resistivity of a hard rock aquifer in the Jangaon sub-watershed, Hyderabad, India. Petrophysical relations have been used to transform resistivity distribution into transmissivity and natural recharge distribution. The coherence of geo-electrically derived parameters has been tested by integrating them into a groundwater flow model. This was performed using MODFLOW codes during one hydrologic cycle within two time periods; time period one coinciding with the rainy season, when there is recharge to the aquifer with no pumping occurring at observation boreholes. During the second time period, dry conditions prevail, hence there is no recharge but observation boreholes are pumped. At the end of the simulation period, simulated groundwater water heads were compared with the observed hydraulic heads and a close match between the observed hydraulic heads and simulated heads has shown the reliability of geo-electrical data as a means of estimation of hydraulic parameters.

Keywords: Hydrogeological characterization, Geo-electrical data, groundwater flow model