Study of ground water in a village of coastal West Bengal using geo-electrical method

Abstract

The productivity of Coastal West Bengal is low. This is mainly due to high ground water salinity particularly in rabi season. In many areas ground water may occur in perched aquifer at greater depths (>40 m and up to 300 m) which is non saline and available for cultivation of crops. Geological information and bore hole statistics of an area help in assessing potential ground water of the area.  Since ground water salinity changes in different seasons in the area, there is a need to assess ground water salinity in different seasons.  The intrusion of saline ground water from nearby river in different locations of adjacent villages may also make the area saline. The sea water inundation during monsoon due to high rainfall or cyclone leaves salts in the soil and makes soil saline Therefore, it is necessary to study ground water potential and quality in different seasons in these villages.  Resistivity Sounding (VES) assuming Schlumberger configuration were carried out in 12 locations in a sea water inundated village (Kanthalberia) of Coastal West Bengal. Ground water samples from nearby tube well (of VES points) were also collected . Four to five geo-electrical layers were found out in the area within a depth of 60 m below ground level. The inter relationship between longitudinal unit conductance (S) and EC of ground water samples showed that EC values increased linearly with S values. S values were positively correlated with EC2 of soil samples. The transverse unit resistance (T) was negatively correlated with EC2 of soil. Chemical analysis of ground water samples showed that the quality of water was good with low salinity and low alkali hazard and could be grouped as C2/3S1 of USDA irrigation water quality classification.

Keywords: Ground water, coastal area, geo-electrical method