Assessment of groundwater vulnerability mapping using AHP method in coastal watershed of shrimp farming area

摘要

Groundwater regions in coastal aquifers are highly vulnerable with increase in urbanization, industrialization and sea water intrusion. The present study attempts to evaluate the vulnerability of groundwater in a coastal watershed of shrimp farming areas. The study area is categorized in the GIS-based AHP environment into three ranges (high, medium, and low vulnerability) using various groundwater parameters such as electrical conductivity (EC), total dissolved solids (TDS), sodium percentage (Na%), total hardness (TH), revelle coefficient, sodium adsorption ratio (SAR), permeability index (PI), and residual sodium carbonate (RSC) and their recommended limits. GIS-based AHP weighted index overlay analysis technique has been proven to be a powerful tool to evaluate the distribution of groundwater vulnerability in the study area. The high vulnerable areas were noted in downstream with a strong contamination of the seawater intrusion along the coastal zone and in proximity of the river. Multivariate statistical techniques are also applied to identify and assess the groundwater vulnerability of the study area. The factor analysis revealed that groundwater quality is strongly affected by rock-water interaction, saline water intrusion, and anthropogenic activities. The spatial distribution map of factor-scores showed the gradual variation in groundwater geochemistry from the western part (upstream) to the eastern part (downstream) of the river. The results from the present study revealed that shrimp farming areas have very least or no impact on the groundwater of the region.