JOUR.GEOL.SOC.INDIA, VOL.80, JULY 2012 48 R. B. BINOJ KUMAR AND M. P. DIVYA Spatial Evaluation of Groundwater Quality in Kazhakuttam Block, Thiruvananthapuram District, Kerala R. B. BINOJ KUMAR 1 and M. P. DIVYA 1 Department of Geology, University of Kerala, Thiruvananthapuram 2 Geological Survey of India Email: binojrb@gmail.com Abstract: The groundwater in the study area generally shows an acidic trend as evidenced by the low pH values, particularly in lateritic aquifers. Spatial assessment indicates that the southern part of the coastal aquifers shows elevated pollution levels during post monsoon season. Most of the groundwater is of Na-Cl facies in post monsoon and which slightly changes to Na-Mg-Cl facies during pre monsoon. Inter relationship between chemical parameters were also studied to understand the groundwater facies. Salinity hazard, percentage of sodium, SAR, integrated SAR and EC and RSC, were considered for judging the usefulness of groundwater for irrigation. Landuse map was prepared and water sample locations were superimposed on it, in a GIS platform, to assess the variation in water quality in different landuse classes. The outcome of the present study indicates that the concentration of certain parameters exceeds the recommended limits and hence mitigation measures are needed to be adopted to ensure safe drinking water. Keywords: Groundwater chemistry, Land use, Pollution, Spatial and temporal changes, Kazhakuttam block, Kerala. 8°31' 33" to 8°41' 17", and east longitude 76°47'58" - 76°57' 50". The study area (Fig 1) is bordered by Arabian Sea in the south, Mamam River in the north and the Kadhinamkulam Lake in the west. The study area is a combination of both rural and urban set-up representing coastal and midland geomorphic environment. This reason makes the area interesting to perform a spatial groundwater quality assessment. GEOLOGY OF THE AREA The area is occupied by the geological formations (Fig 2) ranging from Archean to Recent. Most of the formations are overlain by laterite in the midland region and concealed by recent alluvium along the coastal tract. The area is typically a metamorphic terrain and forms a part of Kerala Khondalite Belt. Major litho unit of the area is garnet-biotite gneiss, with or without cordierite and graphite, pyroxene granulites, charnockites and sedimentaries. The rocks are generally migmatised and the degree of migmatisation varies from place to place. Pyroxene granulite is observed in the eastern part of the study area, whereas sandstone and clay with lignite intercalations are found in the central part of the study area. Quaternary strandline deposits covered by beach sands and sand-silt-clay INTRODUCTION The quality of groundwater is influenced by natural and anthropogenic factors and any deterioration in water quality could affect agriculture production and human health. The study area chosen is Kazhakuttam Block, one of the quickly developing area, due to the existence of the famous IT park-the Technopark, Kinfra film city, Info park, Sainik school, University of Kerala, CRPF camp etc. Hence the area is undergoing large scale urbanization and landscape alteration. The major factors distressing groundwater resources in the study area are over abstraction, reclamation of wetlands, infiltration of pollutants from improperly designed landfills and sewage, saline water intrusion from the Arabian Sea and brackish water infringement from Kadhinamkulam Lake. Effort was made to understand the influence of natural and anthropogenic factors on the quality of groundwater. In addition an attempt was also made to assess the influence of aquifer lithology on groundwater quality STUDY AREA Kazhakuttam Block is situated in Thiruvananthapuram district which includes six panchayaths with a total areal extent of 141km 2 . The area lies between north latitude JOURNAL GEOLOGICAL SOCIETY OF INDIA Vol.80, July 2012, pp.48-56 0016-7622/2012-80-1-48/$ 1.00 © GEOL. SOC. INDIA