Abstract
Laboratory experiments and a numerical simulation were performed to investigate the behavior of residual saltwater trapped in a storage area for freshwater after installation of a cut-off wall. First, dispersivities were estimated by image analysis of the results of pulse and continuous injection experiments performed with tracers, and then the estimated dispersivities were validated by numerical analysis and by calculating the analytical solution. The ratio of longitudinal to transverse dispersivity was 20 in a red food dye tracer and 27 in a fluorescent tracer experiment. The saltwater intrusion and removal experiments were reproduced by a SEAWAT numerical model using an estimated dispersivity ratio of 27. Numerical analysis using a fixed longitudinal dispersivity showed that with a dispersivity ratio of 10, the resulting removal time of the residual saltwater was 1.48 and 1.97 times the removal time obtained with a ratio of 27 and 100, respectively. This result shows that transverse dispersion significantly affected the removal process.
