Delineation of Groundwater Pollution Zones around Sewage Farm in the coastal area of Kerala, South India using Geographic Information System Technique

Geographic Information System (GIS), a computer-based technique is used in groundwater management, especially for the estimation of groundwater vulnerability to contamination. The objective of the present study was to delineate the groundwater contamination zones around the Sewage Farm using Geographic Information System. The study area lies between North Latitude 8° 26ʹ 26ʺ to 8° 29' 29" and East Longitude 76° 54ʹ 51ʺ to 76° 57ʹ 33ʺ. Inverse Distance Weighted Method (IDW) interpolation technique was used for the delineation of groundwater pollution zones in the study area. The sampling locations were mapped with the help of Survey of India toposheet of the scale 1:25000 and a handheld Global Positioning System (GPS). Groundwater pollution (stress) zonation in the study area was done on the basis of the selected water quality parameters of 42 groundwater samples (29 dug wells and 13 tube wells) during pre-monsoon, monsoon and post-monsoon seasons. The highly significant water quality parameters selected for the present study included pH, total dissolved solids (TDS), total hardness (TH), total alkalinity (TA) and total coliforms (TC). TC was given more weightage among the selected parameters. Based on the analysis, the entire study area was classified into three distinct zones, viz., low, moderate and high pollution zones. The results of the present study suggested that the extent of groundwater pollution was relatively lower during monsoon, compared to pre-monsoon and post-monsoon seasons, which might be a reflection of enhanced dilution due to heavy monsoon rainfall occurring in the region. Further, during post-monsoon and pre-monsoon seasons, the areal extent of high pollution zone showed close similarity. From the GIS-based analysis for the delineation of groundwater pollution zones over the area, it was inferred that multiple sources such as Sewage Farm, leachates from soak pits/septic tanks and Parvathy Puthanar, a man-made canal, governed the deterioration of groundwater quality in the study area.