Monday, May 7, 2012
A series of three-dimensional hydrodynamic dispersion numerical simulations is performed to analyze density-dependent groundwater flow and salt transport due to groundwater pumping in a fractured porous coastal aquifer system and to suggest optimal location and pumping rate for a pumping well. The coastal aquifer system is composed of the Quaternary alluvium and marine sediments underlain by a series of the Precambrian and Cretaceous rock masses. Such rock masses contain numerous planar geologic structures such as bedding planes, joint sets and a major fault. The upper part of the rock masses forms a weathered zone. A steady-state numerical simulation with model calibration is performed first to obtain initial spatial distributions of density-dependent groundwater flow and salt transport in the coastal aquifer system before groundwater pumping. Such steady-state numerical simulation results are analyzed and are also validated reasonably well with respect to measured groundwater levels and inferred seawater intrusion front lines. A series of transient-state numerical simulations is then performed to obtain spatial and temporal distributions of density-dependent groundwater flow and salt transport in the coastal aquifer system during groundwater pumping at six different potential locations in the bedrock aquifer. Such transient-state numerical simulation results are analyzed to suggest optimal location and pumping rate for the new pumping well using a well response function and a secondary drinking water quality limit of seawater-normalized salt concentration. These numerical simulation results show that hydrodynamic dispersion numerical modeling can be a useful tool for analyzing density-dependent groundwater flow and salt transport due to groundwater pumping in actual three-dimensional fractured porous coastal aquifer systems and for suggesting optimal locations and pumping rates for pumping wells. This work was supported by the Sustainable Water Resources Research Center of the 21st Century Frontier Research and Development Program, Ministry of Education, Science and Technology, Republic of Korea.