Replenishing an unconfined coastal aquifer to control seawater intrusion: Injection or infiltration?

Abstract

In this study, we compare the performances of well injection and pond infiltration in controlling seawater intrusion in an unconfined coastal aquifer through two scenario groups: (1) a single injection well versus an elliptic infiltration pond and (2) an injection-extraction well pair system versus an elliptic infiltration pond-extraction well system. Comparison is based on quantitative indicators that include the interface toe location, saltwater volume, and maximum net extraction rate (for scenario 2). We introduce a method to determine the maximum net extraction rate for cases where the locations of stagnation points cannot be easily derived. Analytical analysis shows that the performances of injection and infiltration are the same, provided that the pond shape is circular. The examination of scenario group 1 suggests that the shape of the infiltration pond has a minor effect on the interface toe location as well as the reduction in the saltwater volume, given the same total recharge rate. The investigation of scenario group 2 indicates, by contrast, that the maximum net extraction rate increases significantly with the increasing ratio of b to a, where a and b are semiaxes of the ellipse parallel and perpendicular to the coastline, respectively. Specifically, for a typical aquifer assumed, an increase of 40% is obtained for the maximum net extraction when b/a increases from 1/200 to 200. Despite that the study is based on a simplified model, the results provide initial guidance for practitioners when planning to use an aquifer recharge strategy to restore a salinized unconfined coastal aquifer.

Timescale and Effectiveness of Residual Saltwater Desalinization Behind Subsurface Dams in an Unconfined Aquifer

“…In coastal regions around the world, groundwater is an important freshwater resource (Lu et al., 2017; Michael et al. 2017; Watson et al., 2010).…”

A Simulation-Optimization Model for Seawater Intrusion Management at Pingtung Coastal Area, Taiwan

“…Various strategies have been proposed in the past decades to protect groundwater [6][7][8][9]. No matter what strategies have been selected, one key to control seawater intrusion is to maintain the proper balance between water being pumped from an aquifer and the amount of water recharging it.…”

Contamination Transport in the Coastal Unconfined Aquifer under the Influences of Seawater Intrusion and Inland Freshwater Recharge—Laboratory Experiments and Numerical Simulations

“…Most of the previous studies have focused on the time and space distribution of salinity in coastal zones, because they were often invaded by seawater [ 3 , 5 , 15 , 16 , 17 , 18 , 19 , 20 ]. There were two types of flow models simulating the mixing zone of seawater intrusion, consisting of the sharp interface model and mixing interface model [ 21 , 22 , 23 , 24 , 25 , 26 , 27 ]. Many analytical solutions were predominantly derived to describe the distribution of seawater intrusion in coastal aquifers (e.g., [ 23 , 28 , 29 , 30 , 31 ]).…”