Simulation of Recovery Options of Brackish Water Aquifer in the Dagu River Area, China

Quarternary alluvial aquifers in the Dagu river region of Qingdao constitute an important coastal watershed with vast fresh groundwater resources and several well fields in operation. This groundwater system has been subjected to heavy drawdown over the last two decades, which has caused serious seawater intrusion. Even the establishment of a subsurface barrier in 1998, 14.9 km² brackish water still remains in the aquifer. A calibrated solute transport model has been used to investigate the hydrodynamic impacts of different aquifer recovery plans to shrink the amount of brackish water. The results indicate that the optimum plan proposed with three steps can rapidly recover the brackish-water aquifer. After three years´ operation, the extent of brackish plume (250 mg/l) will reduce to 2.06 km² and the chloride concentration for most of the residual brackish water will be lower than 450 mg/l.