Comparing the performance of injection and infiltration in controlling seawater intrusion

Abstract:

Among various strategies introduced for controlling seawater intrusion, artificial recharge through either well injection or pond infiltration is used most commonly in practice. In this study, we compare the performance of well injection and pond infiltration in controlling seawater intrusion through two scenario groups. First, a single injection well is compared with an elliptical infiltration pond by assuming that the pond and the well share the same location and the recharge rate. Second, an injection-extraction well pair system is compared with an elliptical pond infiltration-well extraction system by assuming the same condition as in the first scenario and the same location of the extraction well. The quantitative indicators including the interface toe location, saltwater volume, and the maximum net extraction rate are derived analytically using the potential theory. By comparing the two schemes in the first scenario group, it is found that the infiltration pond significantly outperforms the injection well under the condition that the major semi-axis of the ellipse is along the coastline. Importantly, a critical location of the infiltration pond/injection well is found, under which the maximum reduction in the saltwater volume is achieved. The study of the second scenario suggests that the pond-well system significantly outperforms a well-pair system in terms of the maximum net extraction rate, if the major semi-axis of the ellipse is along the coastline. Sensitivity analysis shows that the shape of the elliptical pond (i.e., the ratio of the major semi-axis to the minor semi-axis) is a key design parameter controlling its performance. The analytical analysis in this study provides initial guidance for practitioners when using the aquifer recharge strategy to restore a salinized coastal aquifer.