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Huge seismic waves triggered by massive undersea earthquake off Sumatra in Indonesia caused widespread destruction in terms of loss of life and properties in the coastal stretches of Tamil Nadu and U.T. of Pondicherry on Sunday, 26th December 2004. The devastation wrought by the tidal waves in Nagapattinam, Cuddalore, Tirunelveli and Kanyakumari districts in Tamil Nadu and Pondicherry and Karaikal regions of the U.T. of Pondicherry has been severe when compared to other parts of Tamil Nadu. As a measure of immediate relief to Tsunami-affected villages of Tamil Nadu, Central Ground Water Board constructed six bore wells in the hard rock areas of Tirunelveli district and four tube wells in the sedimentary tracts of Nagapattinam and Cuddalore districts, for augmentation of sources of water supply. TIRUNELVELI DISTRICT The district is underlain by crystalline metamorphic rocks of Archaean age, tertiary sediments and alluvium. Six boreholes have been drilled in Radhapuram and Valliyur blocks of Tirunelveli district during January and February 2005 (see map). The depth of the bore wells varied between 45 and 160 mbgl and the yield of the wells ranged between 0.025 and 0.592 lps. The formations encountered are weathered, fractured and fissured granite gneisses. The thickness of weathering ranged from 5.50 to 19.40 m. One to three water-bearing fractured zones with cumulative thickness ranging from 1.0 to 2.5 m were encountered. The EC of the formation water varied between 565 (at Idinthakarai) to 3350 (at Kattupulli) microsiemens/cm at 25°C. The chloride content ranged from 53 to 1065 mg/l. The EC of formation water in four wells is less than 2000 and in two wells it is more than 2000 microsiemens/cm at 25°C. The fluoride content ranged from 0.3 to 1.49 mg/l, which is within the permissible limits. Four wells yielded water of potable quality have been handed over to user agencies to cater to the drinking water demands in the Tsunami affected villages. Salient Features of Bore Wells Constructed By Central Ground Water Board, South Eastern Coastal Region, in The Hard Rock Terrain In Thirunelveli district, Tamil Nadu
NAGAPATTINAM & CUDDALORE DISTRICTS The coastal tracts of Nagapattinam and Cuddalore districts are underlain by geological formations ranging in age from Pliocene to Recent. Three tube wells were constructed in Nagapattinam and one in Cuddalore district during January to March 2005 for augmentation of sources of water supply in Tsunami-affected villages (see map). The depth of these tube wells ranged between 250 and 350 mbgl. The formations encountered were sand, clay and their admixtures of sandstone, shale, clay stone and limestone. Cement sealing techniques were adopted to tap the fresh water sandwiched between poor quality formation water at appropriate depth. The depth of granular zones tapped ranged from 213 to 338 mbgl. The yield of the wells ranged between 18 and 60 lps. The piezometric head varied between 4.56 and 15.2 mbgl. The tube well constructed at Kohur village in Nagapattinam district recorded the highest yield of about 60 lps during development. The water from this tube well will cater to the drinking water requirements of a population of about 30,857 in the nearby villages (@ 70 lpd for 10 hours pumping). A population of about 59,657 can be catered to by the water available in the four tube wells constructed for Tsunami relief. The EC of the formation water varied between 625 (Thzhangudam) and 2000 (T. Manalmedu) microsiemens/cm at 25°C. The chloride content ranged from 340 to 440 mg/l. Salient Features Of Tube Wells Constructed By Central Ground Water Board, South Eastern Coastal Region, In The Sedimentary Tracts Of Nagapattinam & Cuddalore districts, Tamil Nadu
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