Modeling the dynamics of the freshwater-saltwater interface in response to construction activities at a coastal site

Abstract

A numerical model was developed to evaluate the response of groundwater flow and the fresh-saltwater interface in relation to the construction of a particle accelerator at the coastal plain of Tokaimura, Japan. Undisturbed conditions were initially simulated and validated against field observations as a prerequisite for the analysis of predictive scenarios. Groundwater heads and the shape of the saltwater interface were appropriately described by the model, although it tended to underestimate salinity concentrations. Saltwater penetrated up to 250 m inland during predevelopment conditions, reaching more than 400 m at the dewatering phase. Flushing of entrapped saline groundwater might occur in addition to seawater intrusion. In depth, multiple saltwater fronts develop in response to the hydraulic properties of the sediments. Groundwater discharges offshore through the sandy aquifers, but salinity fronts prevail in the relatively impermeable layers. Routes for freshwater outflow turned into pathways of seawater intrusion during the pumping phase. The equilibrium would be reestablished within 2 years from the end of the stress, with no evidence of a permanent deterioration of neighbor residential wells. Nonetheless, after construction the accelerator forms a barrier that leads to a sharp rise in piezometric levels and creates a new and long-term disequilibrium in the saltwater wedge. Despite further work is still necessary to test many of the ideas proposed, the present study makes a new contribution to enhance the understanding of the processes occurring in coastal aquifers subjected to anthropogenic influence.

Assessment of seawater mixing in a coastal aquifer by high resolution electrical resistivity tomography

“…However, this procedure required lot of efforts and cost. The quality of groundwater in coastal aquifers deteriorate as a result of the over pumping of water that was previously discharged in to the sea (Gallardo and Marui, 2007). This problem is common in coastal areas throughout the world and the same has been reported by many researchers (Apello et al, 1987;Gnanasundar and Elango, 1999;Bakker, 2000;Shammas and Jacks, 2007;Chenini and Khemiri, 2009;Praveena and Aris, 2010).…”

Hydrogeochemical characteristics of groundwater in coastal phreatic aquifers of Alleppey district, Kerala

“…Factor analysis assumes that observed variables are products of linear combinations of some few underlying source variables known as factors. Factor analysis has now been a major tool in the study of groundwater geochemistry as has been demonstrated in several studies (Lawrence and Upchurch, 1983;Briz-Kishore and Murali, 1992;Sabbarao et al 1996;Olobaniyi and Owoyemi, 2006;Aris et al 2007;Gallardo and Marui, 2007;Ramesh Kumar and Riyazuddin, 2008). The present study was set to determine the factors that significantly control the chemistry of groundwater in the phreatic aquifers of Alleppey district.…”

Controlling factors of groundwater hydrochemistry in a small island’s aquifer

“…Basically, the intrusion may be attributed to the over abstraction of groundwater from the aquifer and also from the effect of sea tides (Bear et al, 1999;Abdullah et al, 2002;Gallardo and Marui, 2007). Precipitation of minerals took place during the cation exchange process which was the later effect from the seawater intrusion into the aquifer.…”