Title

Laboratory-scale investigation of saltwater intrusion dynamics in confined aquifers

Date

2023

Abstract

Saltwater intrusion is a major constraint to the optimal use of fresh groundwater from coastal confined aquifers. Excessive groundwater abstraction to meet growing demands from an increasing coastal population and the projected rise in mean sea level from global warming will cause seawater to encroach farther inland and threaten the available groundwater supply. There is not enough information to the distribution and extent of saltwater encroachment. Actual field monitoring is difficult and expensive. Laboratory-scale experiments provide a cheap and easy method to investigate saltwater intrusion. This study aimed to investigate the flow dynamics of saltwater intrusion, including the effects or recharge, using a laboratory-scale confined aquifer setup. A confined aquifer system with pumping and recharge wells was simulated through a flow tank using sand as the porous medium. First, the behavior of the saltwater intrusion was observed using two hydraulic gradients. The higher the hydraulic gradient, the smaller is the saltwater wedge and the lower is the intrusion rate. This followed available mathematical equation of saltwater intrusion in confined aquifers. A difference between the experimental and theoretical toe positions was observed attributed to laboratory scaling effect. Pumping experiment were done at two points with different extraction rates. Results showed that as the pumping rate increases the farther is the advance of the saltwater wedge, indicating a landward migration of the saltwater wedge. A faster rate of advance was also observed with higher extraction rate, but it took longer time to attain equilibrium. Moreover, it was observed that the closer the pumping well to the toe of the saltwater wedge, the farther the induced advance of the saltwater toe. The process of saltwater up-coning into wells near the saltwater wedge was observed during very high extraction rates. Recharge injection were also done at the same two points with different recharge rates. Farther retreats of the saltwater wedge were observed with higher recharge rates and if the recharge well is closer to the toe of the saltwater wedge. These results indicate a more effective control of saltwater intrusion. These results will help in future planning and design of control measures of saltwater intrusion.

Book Title

Evaluation and pilot-testing of shallow tubewells as recharge wells

Language

English

En – AGROVOC descriptors

GROUNDWATER TABLE; SALINE WATER; GROUNDWATER; PERMEABILITY; GROUNDWATER FLOW; DENSITY

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