Preliminary investigation on environmental degradation due to salinization of river and groundwater in Thamirabarani Delta, South India

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1 Indian Journal of Geo-Marine Sciences Vol. 45(9 ), September 2016, pp Preliminary investigation on environmental degradation due to salinization of river and groundwater in Thamirabarani Delta, South India Satheeskumar V 1, T.Subramani 2* 1 Department of Civil Engineering, Government College of Technology, Coimbatore, Tamil Nadu, India. 2 Department of Mining Engineering, Anna University, Chennai , Tamil Nadu, India. *[ geosubramani@yahoo.com; geosubramani@annauniv.edu] Received 23 January 2014; revised 12 March 2014 Present study consists analysis of data such as river discharge, cropping pattern, subsurface lithology and tidal fluctuations collected from Government organizations. Thematic maps pertaining to the study namely, drainage map, geomorphological map, lineament map and land use map were prepared from the satellite imageries. Well inventory survey and ground truth verifications were also carried out in this region. All spatial and non-spatial data were integrated using geographical information system (GIS). A site was selected for the construction of Ogee type of surplus weir across the Thamirabarani River to minimize the salinisation of surface water and groundwater. [Keywords: Seawater intrusion, Environmental degradation, Thamirabarani delta, South India] Introduction Although the world is not yet experiencing a global water shortage, more than 1.2 billion people live in under conditions of physical water scarcity, which occurs when more than 75% of river water flows are withdrawn. [1] Groundwater is the major source of fresh water available in the earth, which is extracted for domestic, agricultural and industrial applications all over the world. [2] It is preferred than the surface water due to its wide distribution and low risk of contamination. Groundwater quality is as important as its quantity. The quality of water is of vital concern for mankind since it is directly linked with human health and welfare. [3] Variation of groundwater quality in an area is a function of physical and chemical parameters that are greatly influenced by geological formations, recharge-discharge mechanisms of groundwater and anthropogenic activities. Groundwater resources are often over exploited from the coastal aquifers, which leads saline water intrusion. Saltwater intrusion occurs in many of the coastal aquifers around the globe. [4] The shape and degree of seawater intrusion in a coastal aquifer depend on several factors. Some of these are natural and cannot be controlled, while others are manmade and could, thus, be managed. [5] Seawater intrusion is defined as a coastal area natural hazard harmful to human life; and includes not only the direct hazard of disastrous seawater caused by storm tide, but also includes the hazard of intruded seawater penetrating into fresh water aquifers. [6] Less than 2% of seawater intrusion in the fresh water can diminish the water portability. [7] When the discharge is higher than the recharge in aquifers with direct dynamic connection to the sea, seawater intrusion takes place. [8] Coastal aquifers in south and southeast Asia are important sources for water supply. India has a very long coast line which is the backbone of its national economy. Three out of the four metros, the major industrial hubs, about one fourth of the country s population and the most fertile [9] agricultural land are situated in this area. Because of long Indian coastline and continuing increasing urbanization along the coastline, there is a need for rational use of groundwater in such region. [10] The coastal areas are often densely inhabited, especially the river deltas where good soil and abundant water availability have been able to support large population centers. [11] The Thamirabarani delta, located between latitudes 08 o 35 to 08 o 45 and longitudes 78 o 00 E to 78 o 10 E in southern Tamil Nadu state, India, is one such important delta where the salinization of river water and groundwater are common. This region is further threatened by the increased saltpan activities. Thus, a detailed study was carried out with the main objective of minimizing salinisation of river water and groundwater. Materials and Methods The trunk system of Thamirabarani River originates 1,500 m above sea-level on a part of the Annamalai range on the eastern slopes of the Western Ghats in the Tirunelveli District of Tamil Nadu and flows through Tirunelveli and Tuticorin districts of the Tamil Nadu state of southern India.

2 SATHEESKUMAR V & T.SUBRAMANI: ENVIRONMENTAL DEGRADATION DUE TO SALINIZATION 1149 From the source to sea, the total length of the river is about 125 Km. Chithar, Pachayar, Manimuthar, Gadananathi and Ramanathi are major tributaries, and the Thamirabarani river drains with its tributaries to an area of about 4400 Km 2. As most of its extensive catchment areas lay in the Western Ghats, the river enjoys the full benefit of both the south-west and north-east monsoons which make the river perennial. Summer showers are also recorded during the transitional period. The regional slope of the basin is towards east. The area of present study falls in the coastal part of Thamirabarani basin, which occupies an area of approximately 500 Km 2 (Fig. 1). Well inventory survey and ground truth verifications were also carried out in this region. All spatial and non-spatial data were finally integrated using geographical information system (GIS) and finally, and a site was selected for the construction of surplus weir across the Thamirabarani River to minimize the salinisation of river water and groundwater. Methodology Data Collection 1. SOI Toposheets 2. Satellite image 3. Borehole lithology 4. Tidal fluctuation 5. River discharge Preparation of Thematic Maps 1. Study area map 2. Drainage map 3. Geomorphology map 4. Lineament map 5. Land use map Field Investigation 1. Ground truth verification of maps 2. Insitu water quality check 3. Salt pan activities 4. Earthen bund Site identification for construction of weir Fig. 1- Location map of Thamirabarani Delta There are five major channels in the Thamirabarani delta distributing the water into sea. The area is intensively irrigated, and natural scrubs are also seen in the distributaries. Many chemical industries are located in this region, which make use of the river water and groundwater for their needs. To achieve the said objective, the methodology has been divided into three major parts namely preparation of thematic maps, data collection and field observations (Fig. 2). Various details such as, river discharge, cropping pattern, subsurface lithology, pumping details and tidal fluctuations were collected from Government organizations. Various thematic maps such as land use map, drainage map, geomorphology map and lineament map pertaining to the study were prepared from the IRS ID LISS-III satellite imageries. 1. River profile at the proposed site 2. Subsurface condition 3. Maximum tidal rise 4. Maximum flood level 5. Maximum flood discharge Fig. 2- Methodology adopted for the study Results and Discussion Mixing of seawater with river water is a common phenomenon in the Thamirabarani delta, which leads to unsuitability of river water for drinking, irrigation and industrial purposes. Temporary earthen bunds (Fig. 3) have been constructed by the residence of the area across the river channels to minimize the seawater entry. These bunds are frequently washed off during heavy rainy seasons and floods. Thus, this is not an effective measure to minimize the problem. It is further noticed that there has been a considerable increase in the number of saltpans in this region. Due to the increase of saltpans in the recent years, groundwater quality is getting

3 1150 INDIAN J. MAR. SCI., VOL. 45, NO. 9 SEPTEMBER 2016 deteriorated. To get more revenue, formers convert the fertile agricultural lands into saltpans (Fig. 4). As saline groundwater is denser than seawater, saline groundwater is being pumped out from the deeper aquifers for saltpan activities. This could be one of the reasons for seawater intrusion in the aquifers. Fig. 3- Earthen bunds across distributaries of Thamirabarani River Fig. 4- Agricultural lands converted into saltpans Five major distributaries and many small river channels are forming the Thamirabarani Delta(Fig. 5). The Manimuthar main canal and Eral canal are running parallel in the south and north of the Thamirabarani River respectively. Numerous tanks exist in the study area, which are well connected by canals. IRS 1D LISS-III false colour composite satellite image of 23.5m resolution (Fig. 6) was used to prepare geomorphology map, lineament map and land use map. Geomorphologically the area contains flood plains, delta fronts, beach ridges, structural hills, sand dunes and swamps (Fig.7). About 75% of the study area is occupied by flood plains and delta fronts. Flood plains occupy western and northern parts whereas the delta fronts occupy the eastern part. Structural hills and sheet rocks are noticed in the northwestern part of the study. Stabilized sand dune exists in the southern part where there is lot of cashew forms. Beach ridges and black swamps are seen all along the coast of Thamirabarani delta. Lineaments were identified from the satellite imageries and marked on the geomorphological map (Fig. 7). Most of the lineaments trend in NW-SE direction and others are in NE-SW direction. Knowledge of land use is important for many planning and management activities concern with the surface of the earth. More recently satellite imageries have been utilized for land use mapping. [12] About 75% of the land is intensively irrigated in this region (Fig. 8). Dry crops are sowed in the western and northwestern part of the study area. Saltpans are distinctly noticed in the south of Thamirabarani Delta. Well inventory and field survey indicate that some of the wells are affected by seawater intrusion. The total dissolved solids (TDS) and salinity values are increasing in the river water during high-tide period, which lead the water unsuitable for drinking, agricultural and industrial purposes. Temporary earthen bunds are constructed by the farmers to restrict the seawater entry into the river channels. These earthen bunds are frequently washed away by the river flow. Hence, this method is ineffective to solve the problem. Therefore, the study proposes the construction of permanent surplus weir across the main river near Mukkani village. The following field observations were made at the proposed site: (i) the span width of the river is 380m, (ii) the river bed is +1.2m above mean sealevel, (iii) the maximum tidal rise is +1.5m above mean sea-level, (iv) nature of the river bed is sandy, (v) maximum flood level is +6m above mean sea-level and (vi) the maximum flood discharge is 2000 m 3 /s. The construction of weir will also facilitate groundwater recharge in this region.

4 SATHEESKUMAR V & T.SUBRAMANI: ENVIRONMENTAL DEGRADATION DUE TO SALINIZATION 1151 Fig. 5- Drainage map Fig. 6- Satellite image of the study area

5 1152 INDIAN J. MAR. SCI., VOL. 45, NO. 9 SEPTEMBER 2016 Fig. 7- Geomorphology and lineament map Fig. 8- Land use map

6 SATHEESKUMAR V & T.SUBRAMANI: ENVIRONMENTAL DEGRADATION DUE TO SALINIZATION 1153 Conclusion Saline water intrusion is the main threat in the coastal Thamirabarani Basin, which leads the river water and groundwater unsuitable for drinking, irrigation and industrial purposes. Increased saltpan activities in the recent past have also contaminated the land and water resources. Considering the above environmental degradation, the present study concludes that an Ogee type of surplus weir can be constructed across the Thamirabarani River near Mukkani village to minimize the salinisation of surface water and groundwater resources. The weir can be further utilized for diverting the river water to the salt affected areas for reclamation of the contaminated land. It is further suggested that over exploitation of groundwater and the saltpan activities are to be restricted. References 1 WHO/UNICEF. (2006). Meeting the MDG drinking water and sanitation target: The urban and rural challenge of the decade, WA Ragunath, H.M. (1987). Groundwater, Wiley Eastern Ltd., New Delhi. 3 Srinivasamoorthy, K., Vasanthavigar, M., Vijayaraghavan, K., Sarathidasan, R. and Gopinath. S.(2011). Hydrochemistry of groundwater in a coastal region of Cuddalore district, Tamil Nadu, India: Implication of quality assessment; Arab Journal of Geosciences, DOI /s Amer, A.M. (1995). Saltwater intrusion in coastal aquifers, Proceeding of the international conference on water resources management in arid countries, Muscut, Sultanate of Oman, Vol.2, pp Sherif, M. and Kacimov, A. (2007). Seawater intrusion in the coastal aquifer of Wadi Ham, UAE: a new focus on groundwater-seawater interactions, Proceedings of symposium HS 1001 at IUGG, Perugia. IAHS Publ. 312, IAHS, Wallingford, UK, pp Meng Guang-Lan., Han You-Song., Wang Shao-Qing. and Wang Zhen-Yan. (2002). Seawater intrusion types and regional divisions in Southern coast of Laizhou Bay, Chinese Journal of Oceanology and Limnology, 20, P , (2002) 7 Custodio. (1987). Groundwater Problems in coastal areas, Studies and Reports in Hydrology, UNESCO, Paris. 8 Shammas, M.I. and Jacks, G. (2007). Seawater intrusion in the Salah plain aquifer, Oman, Environmental Geology, 53, pp Dhiman, S.C. and Thampi, T.S. (2002). Groundwater Management in Coastal Areas, Central Groundwater Board (CGWB) Report. 10 Naveen Pareek., Mahesh Kumar Jat. and Jain. S.K. (2006). The utilization of brackish water, protecting the quality of the upper fresh water layer in coastal aquifers, Environmentalist, 26, pp Volker, A. (1983). Rivers of SE Asia: their regime, utilization and regulation. Hydrology of humid tropical regions, IAHS Publication, Vol.140, pp Lillesand, T.M. and Keifer, R.W. (1994). Remote sensing and image interpretation, John Wiley & Sons Publication, 3 rd edition, New York.