Amit K Bhattacharya
Department of Geology & Geophysics India
Email: [email protected]
The coastal aquifers often constitute the only source of fresh water. Overuse of groundwater affects its quality and quantity. It causes rapid decline in groundwater level leading to salt water intrusion. Again, any change in the sea level elevation will have the same effect. The objective of this study was to map the vulnerability zones of a coastal area to salt water intrusion in the existing sea level conditions as well as due to assumed 0.5 m sea level rise, using GALDIT method following an integrated remote sensing and GIS, and modelling approach. It was also intended to estimate the areal extents of different landuse classes falling within the different vulnerability zones. The area selected for this study was the coastal belt of Puri district, Orissa, India. The satellite IRS 1D LISS III digital data was used for landuse classification, which demarcated six classes, viz., agricultural land, barren land, plantation, alluvium/beach, water bodies and settlement. Six parameters, forming the acronym GALDIT, viz., aquifer type, aquifer hydraulic conductivity, aquifer thickness, depth to ground water level, distance from shore and impact of sea water intrusion were considered for vulnerability study. A suitable ranking system was devised to give the relative importance of the GALDIT factors and to different categories within each GALDIT factor. Based on that a quantitative estimate of GALDIT index was computed, which has been used for classifying the vulnerability zones. Finally, from these thematic maps, namely, landuse and GALDIT index (vulnerability) map, areal extents of different landuse classes falling in different vulnerability zones were estimated. The study reveals that the northeastern coastal tract of the study area covered by agricultural land and settlements are the most vulnerable zones, while most of the inlands are least or moderately vulnerable to salt water intrusion. Areas likely to be affected more due to an assumed sea level rise of 0.5 m are the agricultural land, barren land, and plantations.