Study on the hydrogeochemical characteristics in groundwater, post- and pre-tsunami scenario, from Portnova to Pumpuhar, southeast coast of India

Abstract

Natural hazards cause great damage to humankind and the surrounding ecosystem. They can cast certain indelible changes on the natural system. One such tsunami event occurred on 26 December 2004 and caused serious damage to the environment, including deterioration of groundwater quality. This study addresses the groundwater quality variation before and after the tsunami from Pumpuhar to Portnova in Tamil Nadu coast using geochemical methods. As a part of a separate Ph.D. study on the salinity of groundwater from Pondicherry to Velankanni, water quality of this region was studied with the collection of samples during November 2004, which indicated that shallow aquifers were not contaminated by sea water in certain locations. These locations were targeted for post-tsunami sample collection during the months of January, March and August 2005 from shallow aquifers. Significant physical mixing (confirmed with mixing models) within the aquifer occurred during January 2005, followed by precipitation of salts in March and complete leaching and dissolution of these salts in the post-monsoon season of August. As a result, maximum impact of tsunami water was observed in August after the onset of monsoon. Tsunami water inundated inland water bodies and topographic lows where it remained stagnant, especially in the near-shore regions. Maximum tsunami inundation occurred along the fluvial distributary channels, and it was accelerated by topography to a certain extent where the southern part of the study area has a gentler bathymetry than the north.

Application of Hydro-Geochemical and Geo-Electrical Techniques to Identify the Impact of Tsunami in the Coastal Groundwater

“…The factor analysis was carried out by using Varimax rotation. Factor analysis carried out by Chidambaram et al (2010) for the study area indicate that three prominent factors were extracted for pre-tsunami and January and two factor for the month of August and March. The first component of factor loading ( Figure 7a) in Pre-tsunami was represented by HCO 3 , Mg, and Na indicating the process of weathering.…”

“…The samples of August identified to have good correlation with seawater composition and that of salt precipitate. Their corresponding pre-tsunami compositions were used to obtain the mixing proportion (Chidambaram et al 2010). So the pre-tsunami water chemistry of the region is taken for the representative locations and the amount of mixing has been calculated.…”

“…It is also noted that the bathymetry is gentle in the southern part of the area, where the tsunami water might have entered a long distance inland, where the inundation was favoured by the distributary's channels and river mouth. Chidambaram et al (2010) inferred that these processes (Fig. 9) might have been controlling the hydrogeochemical changes of ground water after the tsunami.…”

Tsunamis as Long-Term Hazards to Coastal Groundwater Resources and Associated Water Supplies

“…A predominant part of these populations are poor farmers and fishermen who live in dispersed communities along the coast, but with locally relatively high population densities. Though the 2004-tsunami waves reached relatively short distances inland, up to 2 km (Chidambaram et al, 2010, Kume et al, 2009Villholth et al, 2005), and hence alternative water sources from further inland could temporarily replace damaged ones, the immediate and longer-term impacts were considerable.…”

Relevance of water quality index for groundwater quality evaluation: Thoothukudi District, Tamil Nadu, India

“…Groundwater occurs in the weathered portion, along the joints and fractures of the rocks. Numerous studies have concentrated on groundwater quality monitoring and its suitability for drinking, domestic and agricultural uses in the recent decade (Bahar and Reza 2009;Chidambaram et al 2010;Zhao et al 2011;Subba Rao et al 2012;Singaraja 2015). Among the sources of contamination, agriculture has both direct and indirect effects on groundwater chemistry (Jalali and Kolahchi 2008;Thivya et al 2013b).…”