Numerical assessments of recharge-dominated groundwater flow and transport in the nearshore reclamation area in western Taiwan
- 36 Downloads
This study employed experimental and numerical methods to assess the behavior of conservative solute transport for a selected temporary solid waste site in a reclamation area in western Taiwan. Calibrating a site-specific numerical model, finite element model of water flow through saturated-unsaturated media (FEMWATER), relies on observations from field- and laboratory-scale hydraulic tests and spatial-temporal monitoring. The field-scale experiment used a modified hydraulic tomography survey (MHTS) to identify near surface aquifer stratifications and estimate the distribution of saturated hydraulic conductivity. The pressure plate experiments provided parameters for the van Genuchten soil characteristic model. Sensitivity analyses were then conducted based on varied recharge rates and dispersivities applied to the calibrated model. Observations of groundwater levels and salinity in the wells indicated that the regional groundwater flow was from southeast to northwest. In addition, a shallow freshwater layer was noted in the study area. The tidal-induced amplitudes for water level fluctuation in the wells ranged from 2 to 20 cm, depending on their distance from the seawater body. MHTS showed clear stratification, similar to that of well loggings at the storage site. The hydraulic conductivity at the test site ranged from 8 to 10 m/day, which is close to that obtained from the laboratory falling head test. The results of particle-tracking modeling showed that the critical recharge rate for the site needed to enhance plume traveling is 1000 mm/year. The increase in dispersivity values induced a decrease in plume travel time of up to 1000 days from the site to the coastal line. A special case for pulse releasing solute at the site shows that the key factor in controlling plume migration is the recharge rate. This is due to the low natural head gradient in the reclamation area. The results therefore suggest that a land drainage system near the site can play an important role in contaminant transport in the reclamation area.
KeywordsReclamation area Numerical model Solute transport Solid waste site Hydraulic tomography
This research was supported by Dragon Steel, under grant 14C1M0014, and partially supported by Soil and Groundwater Pollution Remediation Fund in 2017 and 2018, by the Institute of Nuclear Energy Research under grant NL1030099, and by Water Resources Planning Institute under grant 107705.
- Bohling, G. C., Butler, J. J., Zhan, X., & Knoll, M. D. (2007). A field assessment of the value of steady shape hydraulic tomography for characterization of aquifer heterogeneities. Water Resource Research, 43(5), W05430. https://doi.org/10.1029/2006WR004932.
- Brovelli, A., Mao, X., & Barry, D. A. (2007). Numerical modeling of tidal influence on density dependent contaminant transport. Water Resource Research, 43(10), W10426. https://doi.org/10.1029/2006WR005173.
- Butler, J. J. (1997) The design, performance, and analysis of slug tests. Boca Raton: CRC Press, p. 262.Google Scholar
- Chang, S. W., & Clement, T. P. (2012). Experimental and numerical investigation of saltwater intrusion dynamics in flux controlled groundwater systems. Water Resource Research, 48(9), W09527. https://doi.org/10.1029/2012WR012134.
- Garbossa, L. H. P., Souza, R. V., Campos, C. J. A., Vanz, A., Vianna, L. F. N., & Rupp, G. S. (2016). Thermotolerant coliform loadings to coastal areas of Santa Catarina (Brazil) evidence the effect of growing urbanisation and insufficient provision of sewerage infrastructure. Environmental Monitoring and Assessment, 189(1), 27.CrossRefGoogle Scholar
- Illman, W. A., Liu, X., Takeuchi, S., Yeh, T. C. J., Ando, K., & Saegusa, H. (2009). Hydraulic tomography in fractured granite: Mizunami underground research site, Japan. Water Resource Research, 45(1), W01406. https://doi.org/10.1029/2007WR006715.
- Lin, H. C. J., Richards, D. R., Yeh, G. T., Cheng, J. R., & Cheng, H. P. (1997). FEMWATER: A Three-dimensional finite element computer model for simulating density-dependent flow and transport in variably saturated media (No. WES/TR/CHL-97-12). Vicksburg: Army engineer waterways experiment station vicksburg ms coastal hydraulics lab.Google Scholar
- Straface, S., Yeh, T. C. J., Zhu, J., Troisi, S., & Lee, C. H. (2007). Sequential aquifer tests at a well field, Montalto Uffugo Scalo, Italy. Water Resource Research, 43(7), W07432. https://doi.org/10.1029/2006WR005287.
- Van Genuchten, M. Th., Leij, F. J., & Yates, S. R. (1991). The RETC code for quantying the hydraulic functions of unsaturated soils; EPA/600/2-91/065. In R. S. Kerr (Ed.), Environmental Research Laboratory. ADA: U.S. Environmental Protection Agency.Google Scholar
- Xia, Y., Li, H., Boufadel, M. C., & Sharifi, Y. (2010). Hydrodynamic factors affecting the persistence of the Exxon Valdez oil in a shallow bedrock beach. Water Resource Research, 46(10), W10528. https://doi.org/10.1029/2010WR009179.
- Zha, Y., Yeh, T. J., Illman, W. A., Tanaka, T., Bruines, P., Onoe, H., Saegusa, H., Mao, D., Takeuchi, S., & Wen, J. (2016). An application of hydraulic tomography to a large-scale fractured granite site, Mizunami, Japan. Groundwater, 54, 793–804. https://doi.org/10.1111/gwat.12421.CrossRefGoogle Scholar
- Zhu, J., & Yeh, T.-C. J. (2005). Characterization of aquifer heterogeneity using transient hydraulic tomography. Water Resource Research, 41(7), W07028. https://doi.org/10.1029/2004WR003790.