A Study on Groundwater Quality in the Pondicherry Region
Total Page：16
File Type：pdf, Size：1020Kb
ECO-CHRONICLE 85 ECO-CHRONICLE, Vol.3., No. 2. June 2008, pp: 85 - 90 A STUDY ON GROUNDWATER QUALITY IN THE PONDICHERRY REGION Pethaperumal, S.1, Chidambaram, S.3, Prasanna, M.V. 3, Verma, V.N.2, Balaji, K. 3, Ramesh, R. 3, Karmegam, U. 3, and Paramaguru, P. 3 1 State Ground Water Unit, Department of Agriculture, U.T. of Pondicherry. 2 Joint Director of Agriculture, Department of Agriculture, U.T. of Pondicherry 3 Department of Earth Sciences, Annamalai University, Annamalai Nagar, Tamil Nadu. ABSTRACT The Pondicherry region is characterized by different geological formations, and groundwater is the major source for domestic, agriculture and other water-related activities. Hydrogeochemical analysis of groundwater was done to assess the quality of groundwater for drinking and agricultural + + + + - purposes. Chemical parameters of groundwater such as pH, EC, TDS, Na , K , Ca , Mg , Cl-, HCO3 - , SO4 , PO4 and H4SiO4 were determined. Interpretation of analytical data shows that Ca-Na, Cl-SO4- HCO3 is the dominant facies in the study area. Groundwater in the area is generally hard and fresh brackish in nature. High EC and TDS in a few locations indicates its the unsuitability for drinking and irrigation. Such areas require special care to provide adequate drainage and introduce alternative salt tolerance cropping. INTRODUCTION bounded on the east by Bay of Bengal and on the remaining sides by lands of South Groundwater contains dissolved minerals Arcot district. The region is 293 sq. km. in from the soil layers through which it passes. extent and consists of 179 villages. The It may also contain some harmful Pondicherry region, in general is a flat contaminants through the process of peneplain with an average elevation of about seepage from the surface water and 15m above MSL. The terrain becomes a biological activities. On the other hand, the little undulating with prominent high grounds surface water contains a lot of organic varying from 30 to 45m above MSL towards matter, mineral nutrients and other interior northwest and north eastern part of contaminants brought by run off from the region. Three major physiographic units agriculture fields such as fertilizers, are generally observed namely (i) Coastal pesticides, soil particles, waste chemicals plain (ii) Alluvial plain and (iii) Uplands. from industries and sewage of cities and There are two major rivers draining the rural areas. These water are also inturn Pondicherry region namely the Gingee river infiltrates into the subsurface. In the present in the north and Ponnaiyar river in the south. study a detailed investigation on ground The Gingee river runs for 34 km in the region water quality of Pondicherry was carried out before joining the Bay of Bengal. The mean with respect to various aquifer systems. monthly temperature ranges between 22° C and 33° C. The average annual rainfall at The area chosen, Pondicherry is located on Pondicherry is 1254.4mm (CGWB, 1993). the east coast of India forming enclaves The geology of the area includes alluvium, within the South Arcot district of Tamilnadu. tertiary and cretaceous sedimentaries It is bounded by north latitudes 11° 45’ and underlined by crystallines. 12° 03’ and east longitudes 79° 37’ and 79° 53’ and forms parts of survey of India MATERIALS AND METHODS topographical maps no 58M/9, M/13, and 57P/12 and P/16 (Fig 1). The region is 44 water samples from bore wells were 86 ECO-CHRONICLE collected during the south west monsoon 1994). Silica is the second most abundant 2006 in order to cover different litho units of element in the earth crust and essential the study area from the Alluvium (11), component of almost all minerals. Tertiary (Upper cuddalore sand stone) (9), Bicarbonate is the dominant anion followed Tertiary (Lower cuddalore sand stone) (15) by Chloride, Sulfate and Phosphate and Cretaceous (9) (Fig 1). The samples irrespective of terrains. were analyzed using standard procedures (APHA, 1998). Cations RESULTS AND DISCUSSION Sodium is the important and most abundant alkali metal which is highly mobile A maximum, minimum and average value and soluble in groundwater. Potassium in for the chemical composition of groundwater is generally lesser due to its groundwater is given in the Table 1. higher stability (Herman Bouwer, 1978). The dominant cations are as follows Na+ > Ca2+ Hydrogeochemistry > Mg2+ > K+ in Alluvium, Tertiary (upper) and Anions Cretaceous formations. In Tertiary (lower) formation, Sodium is the dominant cation Bicarbonate represents the major sum of followed by Magnesium, Calcium and alkalinity. Alkalinity in water is the measure Potassium. of its capacity of neutralization. It is formed mainly due to the action of atmospheric CO2 Water Quality and CO 2 released from organic decomposition. Cl- is higher indicating the The voluminous raw hydrogeochemical saline water intrusion and Base Exchange data analyzed is often processed manually reactions (Freeze and Cherry, 1979) Sulfate for interpretation. To simplify the is found in water due to its lesser breaking interpretation of the data, a computer down of organic substances from programme WATCLAST in C++ weathered soil/water and due to the (Chidambaram, 2003), which was used for influence of saline waters (Miller, 1979; calculation and graphical representations (Table 1). Ca-Na and Cl-SO -HCO is the Craig and Anderson, 1979; Singh et al., 4 3 ECO-CHRONICLE 87 dominant facies irrespective of terrain in the Lower) formation, hardness varies from soft study area. to moderately hard. Similar trend was observed in Cretaceous formation. Hardness of the water refers to the soap neutralizing power of water. Hardness refers Na is an important cation which in excess to the reaction with soap and scale deteriorates the soil structure and reduces formation. It increases the boiling point and crop yield (Srinivasamoorthy, 2005). SAR do not have adverse effect on health of values in all the major litho units ranges human. Temporary hardness (TH) is higher from excellent to good category. According in all litho units when compared to the non to Wilcox classification (1955) the water is carbonate hardness (Table 2). Hardness classified based on the Na% with respect in Alluvium varies from slightly hard to to the other cations present in water. The moderately hard. In Tertiary (Uppper and Na% is expressed by Wilcox (1955) and Eaton (1950). Table 1. Geological Succession of the Study area ERA PERIOD FORMATION LITHOLOGY Quarternary Recent Alluvium Sands, Clays, Silts,Kankar and Gravels Sandstone, Pebbly and gravelly Tertiary Mio-Pliocene Cuddalore and coarse grained with minor clays and silt stones and thin seams of lignite -----------------------------UNCONFORMITY------------------- Tertiary Palaeocene Manaveli Yellow and Yellowish brown, greay calcarious siltstone and claystone and shale with thin bands of limestone. Yellowish white to dirty white, Tertiary Palaeocene Kadapepperikuppam sandy, hard fossiliferous limestone, calcareous sandstone and clay. ----------------UNCONFIRMITY-------------------- Mesozoic Upper Turuvai Limestone Highly fossiliferous limestone, Cretaceous conglomeritic at places, calcareous sandstone and clays Upper greyish to greyish green Mesozoic Cretaceous Ottai Claystone claystones, siltstone with thin bands of sandy limestone and fine grained calcareous sandstone. Upper QuartzoseQuartzos sandstone, hard coarse Mesozoic Cretaceous Vanur Sandstone grained, occasionally felspathic or calcareous with minor clays. Mesozoic Lower Ramanathapuram Black carbonaceous, silty clays and Cretaceous (unexposed) fine to medium grained sands with bands of lignite and sandstone, medium to coarse grained. ---------------UNCONFIRMITY----------- Achaeans Eastern Ghats Charnockite and biotite hornblende complex gneisses 88 Table 2. The Maximum, minimum, and average of the 44 samples collected (all values are in mg/l except, EC in μs/cm and pH) ECO-CHRONICLE ECO-CHRONICLE 89 ALL ALL - Alluvium, TER (U) - Upper TERTertiary, (L) - Lower CRETertiary, - Cretaceous Table Table 3. Summary of the geochemical characters of the groundwaters in different Stratigraphic units 90 ECO-CHRONICLE Chloro-alkaline indices i.e. CAI1 and CAI2 Chidambaram, S., Ramanathan, A. L., are used to measure the extent of Base Srinivasamoorthy, K. and Anandhan, P., Exchange during rock water interaction. 2003. WATCLAST – A Computer Program There is an exchange of Na and K in for Hydrogeochemical Studies, Recent groundwater with Mg or Ca in rock matrix trends in Hydrogeochemistry (case studies when both the indices are positive. All the from surface and subsurface waters of ionic concentrations are expressed in epm. selected countries). Published by Capital Majority of samples show negative values Publishing Company, New Delhi, 203 - 207. in all the litho units. Craig, E. and Anderson, M. P. 1979. The In Scholler (1967) classification of water effects of urbanization of groundwater types (Table 2), majority of samples quality. A- Case study of groundwater. 17. irrespective of terrains fall in type I with minor 456 – 562. representation in type II and type III, indicating longer residence time of water Eaton, E. M., 1950. Significance of with more prominent Base Exchange. Carbonate in irrigation water, Soil Science, v.69, pp.123 – 133. CONCLUSION Freezy, R. A. and Cheery, J. A., 1979. Interpretation of hydrochemical analysis Groundwater. Prentice Hall, Englewood reveals that the groundwater in Pondicherry Cliffs. region has slightly hard to moderately hard category and requires softening