Hydro-Geophysical Study for Well Design in Lower Reaches of Kasai River Basin, Eastern India

Saltwater intrusion and up coning in coastal aquifer is a common phenomenon brought either due to flow of seawater into freshwater aquifer originally caused by groundwater abstraction near the coast or due to wrong casing design of water wells. This necessitates a study of aquifer disposition along with demarcation of fresh water saline water interface of Kasai River basin, Eastern India to determine the depth to freshwater and recommend the borehole design. In this study geophysical and hydrogeological techniques were employed to map to demarcate fresh and saline water interface. The phenomenon of saline water up coning is also noticed and accordingly water wells have been designed. For the said study, twenty two geophysical logs, sixty five lithological logs and hydrogeological data of eighty eight sites spread across Kasai River basin were utilized. The study shows that there are three regional aquifers exist in the area. It is recommended that water wells in the study area is to be constructed with artificial gravel packing of size 2-3mm and screen slot size is suggested to be 1.2mm. Since the sites are affected with saline water, hence isolation of zone is mandatory with proper cementing material or packer. This research work is able to develop a design model for the boreholes located in the area. The work as a whole will serve as a vital role in scientific management of groundwater resource and enable the rational planning in coastal aquifers so as to avoid fresh and saline water intermixing and up-coning.