Parameter Estimation in Coastal Phreatic Aquifer near Mukka (Karnataka, India)

Abstract:

The solution of the inverse problem for saltwater intrusion processes has not been studied as extensively as solution for forward saltwater intrusion problems. In forward modeling of large scale heterogeneous aquifers, often information on spatially distributed flow-transport parameters are unknown. In the present study variable-density groundwater model is coupled with inverse numerical code and also with genetic algorithms to estimate the flow-mass transport parameters in a coastal phreatic aquifer for vertical cross section and for spatial distribution. The area under investigation lies on the west coast of India, approximately 17 km from the Mangalore City. The aquifer has sea along the west, tidal river along northern and other boundaries are considered as no freshwater flux. Data from the electrical tomography and borehole logging, which was carried out by other researchers in the study area is considered for zoning of aquifer. Most of the wells in the study area are of large diameter and shallow therefore it is necessary to estimate the storage parameter in each layer. The spatial characterization of the aquifer involves pumping tests, vertical electrical sounding, and water quality analysis carried out for monitoring wells. The resulting inverse model estimates the parameter for flow and transport processes, based on the measured data of spatial and temporal distributions of head and salinity in the monitoring wells. The parameters estimated from the inverse modeling are validated by comparing with the available results of pumping tests, vertical electrical sounding, electrical tomography and borehole logging. The inverse model is cross verified by forward simulating the extent of saltwater intrusion with the available hydrological and hydro-geological parameters. The regional scale inverse model can be extended to large scale modeling for the better development and management of groundwater in coastal regions.