HYDROGEOLOGICAL INVESTIGATION AND GROUNDWATER MODELING FOR AQUIFER CHARACTERIZATION

Abstract

The focus of this dissertation is to determine the different aquifer systems and their characteristics using integrated hydrogeological studies aided by groundwater modeling techniques. The area of about 637 sq. km. has been taken for current study which is a part in and around Bhopal city of the central India. This study has been divided into two stages, first stage includes the hydrogeological investigation using suitable techniques and the second stage is concerned with the use of obtained information to develop a 3-D stratigraphic model followed by running a groundwater flow model. The literature on hydrogeological investigation, geophysical techniques and groundwater modeling has been explored and reviewed in detail and found that it serves the purpose of identifying the available stratigraphic units which subsequently deciphers the sub-surface disposition of aquifer system. Geologically, sedimentary rocks of vindhyan group with deccan trap basalts of high resistivity are present in the area. The geological investigation reveals that the deccan traps spread around an area of 385 sq.km., vindhyan sandstone formation occupies about 120 sq.km. area and the remaining area of around 134 sq.km. is covered by alluvium and soil, Laterite and Sirbu shales.The exploratory bore well data and ground water level data collected from the concern organizations have been analyzed and interpreted for preparation of aquifer maps and depth to water table map of the study area respectively. Trend analysis of groundwater levels has been done for last 15 years data which mostly depicts the declining groundwater level in the study area. The 3-dimesional stratigraphic model generated from the interpreted vertical electrical sounding data using Rockwoks-15 software.The model shows that, there are three-layer rock formations found below the surface which are soil cover at the top, weathered basalt and sandstone rocks, followed by the base of the model consists of consolidated basalt and sandstones which are impermeable in nature. These information’s has been used in the simulation of groundwater flow model using visual MODFLOW.The characterized first aquifer consists of major clay layers, weathered and vesicular basalt, and sand with gravel and is unconfined in nature whose thickness varies from 3 to 30 m. The second aquifer is found in the fractured rocks having thickness between 30 to 200 m.These results of integrated approach are very helpful while making decisions on pinpointing the suitable sites for development and management of ground water resources based on hydrogeological significance