Geochemical Signatures of Groundwater in the Coastal Aquifers of Thiruvallur District, South India
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Appl Water Sci (2017) 7:263–274 DOI 10.1007/s13201-014-0242-2 ORIGINAL ARTICLE Geochemical signatures of groundwater in the coastal aquifers of Thiruvallur district, south India S. Senthilkumar • N. Balasubramanian • B. Gowtham • J. F. Lawrence Received: 5 April 2014 / Accepted: 16 October 2014 / Published online: 4 November 2014 Ó The Author(s) 2014. This article is published with open access at Springerlink.com Abstract An attempt has been made to identify the Introduction chemical processes that control the hydrochemistry of groundwater in the coastal aquifers of Thiruvallur coastal Hydrogeological and geochemical studies are the basis for village of Thiruvallur district, Tamil Nadu, south India. scientific groundwater resource management. Due to the The parameters such as pH, EC, TDS and major ion con- ever increasing demand for potable and irrigation water centrations of Na, K, Ca, Mg, Cl, HCO3,SO4 and NO3 of and inadequacy of available surface water, the importance the groundwater were analyzed. Abundances of these ions of groundwater is increasing exponentially every day are in the following order Na[Ca[Mg[K and HCO3[ (World Bank Report 2010; Selvam and Sivasubramanian Cl[SO4[NO3. The dominant water types are in the order 2012). of NaCl[ mixed CaMgCl [ CaHCO3 [ CaNaHCO3. Seawater intrusion is one of the most common problems Water types (mixed CaHCO3, mixed CaMgCl and NaCl) in almost all coastal aquifers around the globe (Melloul and suggest that the mixing of high salinity water caused from Goldenberg 1997, 1998; Sivakumar and Elango 2008; surface contamination sources such as irrigation return Chidambaram et al. 2009; Mondal et al. 2010, 2011; flow, domestic wastewater and septic tank effluents with Srinivasamoorthy et al. 2011). This phenomenon can be existing water followed by ion exchange reaction pro- explained by a variety of conditions such as gentle coastal cesses, silicate weathering and evaporation are responsible hydraulic gradients, tidal and estuarine activity, sea level for the groundwater chemistry of the study area. The above rises, low infiltration, excessive withdrawal and local statement is further supported by Gibbs plot where most of hydrogeological conditions (Sarma et al. 1982; Longe et al. the samples fall within the evaporation zone. 1987; Rajmohan et al. 2000; Barret et al. 2002; Saxena et al. 2004; Kacimov et al. 2009). The common method for Keywords Groundwater Á Geochemical facies Á Ionic assessing seawater intrusion through an aquifer in coastal ratios Á Thiruvallur coastal village Á Tamil Nadu belts is the periodic analysis of groundwater (Todd 1980; Kim et al. 2009; Mondal et al. 2010, 2011; Krishnakumar et al. 2012). The chemistry of groundwater is an important factor that determines its use for domestic, irrigation and industrial purposes. Interaction of groundwater with aqui- S. Senthilkumar (&) Á B. Gowtham fer minerals through which it flows greatly controls the Department of Geology, Presidency College, Chennai 600 005, groundwater chemistry. India The geochemical properties of the groundwater depend e-mail: [email protected] on the chemistry of water in the recharge area as well as on N. Balasubramanian the different geological processes that take place in the Department of Geology, V. O. Chidambaram College, Tuticorin subsurface. The groundwater chemically evolves due to the 628008, India interaction with aquifer minerals or by the intermixing J. F. Lawrence among the different groundwater reservoirs along the flow Department of Geology, University of Gondar, Gondar, Ethiopia path in the subsurface (Domenico 1972; Wallick and 123 264 Appl Water Sci (2017) 7:263–274 Toth1976). Jalali (2005) reported that the dissolution of Villivakkam and Gummidipoondi along the east coast of carbonate minerals, cation exchange and weathering of Thiruvallur district. Geographically, it extends between silicates control the groundwater chemistry in semiarid 79o550 and 80o250E and 13o000 and 13o350N and covered by region of western Iran. Degradation of groundwater quality survey of India Toposheets No. 66 C 3, 66 C 4, 66 C 7 and in the coastal region generally occurs due to natural pro- 66 C 8 (Fig. 1). The total areal extent of the present study cesses such as saline water intrusion, wind-driven sea spray area is 1,402.79 sq.km. It is surrounded by Poonamallee and and marine aerosols deposited on the top soil, evaporation Poondi blocks in the west, Kancheepuram and Chennai and interaction of groundwater with brines and sedimen- districts along the south, Andhra Pradesh state in the north tary formation (Sanford et al. 2007). Groundwater is the and Bay of Bengal along the east. The study area enjoys most important source for water supply in the coastal tropical climate. The annual mean minimum and maximum regions of Thiruvallur district. Groundwater chemistry of a temperatures are 24.3° and 32.9 °C, respectively. The dis- region is generally not homogeneous and is controlled by trict receives rain under the influence of both southwest and geochemical processes, flow and recharge processes, northeast monsoons. The northeast monsoon chiefly con- evaporation, evapotranspiration and possible presence of tributes to the rainfall to the study area. The average annual contamination sources. Identification of various geochem- rainfall is 1,291 mm. The drainage pattern of the study area ical processes will help to understand the causes for is generally sub-dentritic. Araniyar, Korattalayar, Cooum, changes in water quality due to the interaction with aquifer Nagari and Nandhi are some important rivers drain along material, especially in weathered rock formations. An the eastern part of the study area. All the rivers are seasonal attempt has been made in this study to evaluate the results and carry substantial flows during the monsoon period. of hydrogeochemical study on the coastal part of Thiruv- Korattaliar River water is supplied to Cholavaram and Red allur district of Tamil Nadu, south India. Hill tanks by the Anicut at Vellore Tambarambakkam. Study area Geology The study area is situated in the north of Chennai city The main geological formations occurring in the coast are comprising blocks such as Pulal, Sholavaram, Minjur, upper Gondwana consisting of sand and silts that are Fig. 1 Location map of the study area 123 Appl Water Sci (2017) 7:263–274 265 Fig. 2 Geology of the study area Quaternary sand and clay underlain by tertiary formations clayey sand and sandy clay. As per the Central Ground (Subramanian and Selvan 2001). The study area is equally Water Board (2007), Pulal and Sholavaram blocks are covered by sand, silt and alluvium soil deposits. Regions categorized as semi-critical and Minjur block is overex- around Minjur area are completely covered by coastal ploited. Villivakkam and Gummidipoondi are classified as alluvium which lies in the east coast shoreline (Fig. 2). In being in safe condition among the other blocks of the study rare places, clay deposition is seen. Laterite deposit covers area. Sholavaram area and the rest of the places are covered by sand and silt deposits which extend from the Gummudip- undi block. Along the northern coast of Chennai and Land use/land cover Thiruvallur districts, an arenaceous formation called Co- romandal formation of probable Holocene age has been The Thiruvallur Coast consists of the following land use recorded below the beach sand. This formation is essen- categories such as water bodies, settlement with vegetation tially a quartz arenite which at places grades in depth to and vegetation, shallow water bodies, barren land and sand 123 266 Appl Water Sci (2017) 7:263–274 Fig. 3 Drainage of the study area cover from the result of maximum likelihood supervised Nagari and Nandhi are the important rivers. The drainage classification carried out on enhanced thematic mapper pattern, in general, is dendritic. All the rivers are seasonal (ETM?). A major part of the study area is occupied by the and carry substantial flows during the monsoon period. vegetation cover. Around 579.27 sq. km of the total area is Korattaliar River water is supplied to Cholavaram and Red occupied by vegetation, while around 388.3608 sq. km is Hill tanks by the Anicut at Vellore Tambarambakkam. occupied by barren land, otherwise known as waste land After filling a number of tanks on its further course, the covers. Large water bodes are seen in 187.43 sq.km, river empties into the Ennore creek a few kilometers north whereas shallow water bodies such as ponds and small of Chennai. The Cooum River, flowing across the southern tanks occupy 74.18 sq.km of the study area. Settlements part of the district, has its origin in the surplus waters of the with vegetation cover 164.83 sq.km of the study area. This Cooum tank in Tiruvallur Taluk and also receives the vegetation mainly includes trees such as coconut, mango, surplus waters of a number of tanks. It feeds the Chem- drumstick, neem and some fruit varieties. barambakkam tank through a channel and finally drains into the Bay of Bengal. Drainage Materials and methods The flow of subsurface water in a terrain depends on the drainage pattern. The drainage map of the study area has Fourteen groundwater samples were collected in the entire been prepared (Fig. 3). Araniyar, Korattalayar, Cooum, study area during the pre-monsoon of 2012 and post- 123 Appl Water Sci (2017) 7:263–274 267 monsoon period of 2013. The samples were collected in 1 l TDS is observed (both in pre-monsoon and post-monsoon capacity polythene bottles. Prior to the collection, the seasons) in coastal alluvium formations around Obasamu- bottles were thoroughly washed with diluted HNO3 acid, dram (Loc. No. 2), Kattur (Loc. No. 8) and Kattupalli (Loc. and then with distilled water before filling the bottle with No.9). Wells situated in other geological formations such the sample. pH, EC and TDS were measured at the sample as sandstone and alluvial plains are occupied by fresh- to collection site using a water analysis kit (Deep Vision - medium-quality groundwater.