An Innovative Approach to Assessing the Distribution of Stored Freshwater while Injecting it through a Well Partially Screening the Brackish Aquifer

Over-exploitation of groundwater in the regions favorable for human settlements around the world has raised uncertainties on the sustainability of this precious resource in the future. However, the stress on the fresh groundwater zones can be reduced substantially by managing inland brackish/saline aquifers. Freshwater when available in excess can be stored judiciously in such aquifers for later on use; though a certain quantity of fresh water is lost during its storage and recovery depending upon the in situ groundwater gradient and buoyancy effect (caused due to density difference in the injected and ambient waters). Hence, increasing the efficiency of freshwater recovery was our prime concern, and for which there was a need to know the interface boundaries of freshwater stored in the ambient water. For the purpose, a new method has been developed and proposed in this paper that is based on the hydraulics of an injection well and the breakthrough curve of the injected tracer through the storage medium (i.e. aquifer). The close agreement between the outcome of the proposed model and method with the field observations has validated the acceptance of this innovative concept. The model results show that the shape acquired by the injected freshwater in the brackish/saline aquifer depends upon the screened location of the well about its centerline. Additionally, the storage of freshwater in the upper portion of the aquifer is the most efficient way to minimize its contact with the ambient water and subsequently its loss due to the development of the dispersion zone.