Evaluation of Vulnerability Zone of a Coastal Aquifer Through GALDIT GIS Index Techniques

2019 
Abstract Seawater incursion (SWI) is an universal threat magnified by rising sea levels, climate change, and an escalating dependence of coastal fresh groundwater resources for the water supplies needed. Therefore SWI is intrinsically very difficult and more expensive to examine, investigate, and project. Taking into account abovementioned issues the current study was carried out in the Nagapattinam coastal region, Tamil Nadu, Southern India. The modern technique (GALDIT) was adopted in this study for the identification of SWI in this region. Groundwater samplings were carried out at 30 locations and six hydrologeological parameters were used to obtain information on incursion in the coastal areas. The results were: groundwater occurrence (G) was unconfined, aquifer hydraulic conductivity (A) was ranked as 5–7.5, the depth of the groundwater above sea level (L) was ranked between 2.5 and 7.5, the parameter of the distance from the sea (D) showed the ranking of 7.5–10, the impact of the existing conditions of seawater intrusion in the area (I) was given an index of 7.5–10, and the thickness of the aquifer (T) ranking varied from 2.5 to 10. From the six parameters the calculated GALDIT index was > 7.5; it showed that high vulnerability areas were identified in 23 locations out of the 30. The remaining seven locations were classified as moderate vulnerability. The final output indicates that major portions of the coastal areas are highly affected by seawater.
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