River System and Water Resources
Karaikal region is the deltaic region of the Union Territory which is at the terminus of the river Cauveri. The main branches of Kaveri below Grand Anicut are the Kodamurutti, Arasalar, Virasolanar and the Vikramanar. Although Arasalar and its branches spread through Karaikal, the waters of Kodamurutti and Virasolanar also meet the irrigation needs of the region.
The Arasalar having a total run of 24 km. enters Karaikal region, a little East of Akalanganni. It forms the natural boundary line separating Niravi Commune from Tirunallar on the North-West and Karaikal on the North-East. The Nattar, branching off from Arasalar at Sakkottai in Thanjavur District, runs a distance of 11.2 km. in a South-East direction across Nedungadu and Kottuchcheri Communes before emptying itself into the sea. The Vanjiar fed by Arasalar, takes its course along the Northern boundary of Tirunallar Commune, drops on a South-East curve towards Karaikal Commune and merges with the Arasalar, South- East of Karaikal town after covering a distance of about 9 km. The Nular, also fed by the Arasalar, runs a distance of 13.77 km. before it joins Vanjiar North-East of Karaikal town. The Puravadaiyanar and the Tirumalarajanar are the branches of Kodamurutti. Puravadaiyanar runs through Tirumalarajanpattinam Commune for a distance of 5.3 km. before it empties itself into the sea, South-East of Melvanjiyur. The flow of Tirumalarajanar which forms the natural boundary line between Niravi and Tirumalarajanpattinam communes runs a distance of 5.13 km. before it enters the sea, North of Pattanachcheri. The Nandalar takes off from Virasolan and runs across the Northern boundary of the region through Nedungadu and Kottuchcheri Communes for a distance of about 15.15 km. before it finds its outlet into the sea a little South of Tarangambadi.
Underground water resources :
Karaikal region gets most of its water for irrigation from Kaveri and as such ground water resources in the region have not been fully developed. Here the water table lies at depths of 3-4 metres below ground level and during summer declines to 6-7 metres below ground level. In a number of villages filter point wells piercing sandy materials down to about five metres and fitted with hand-pumps supply fairly good quality water. In many cases the quality of shallow ground water is rather poor. In the past, several attempts were made to tap ground water by means of deep tube-wells for drinking and agricultural purposes.
The region is occupied by alluvium consisting of sands and clays. The alluvium is underlain by the Karaikal beds of Pliocene age consisting of sands, gravels and clay. Wells situated in and around Karaikal range in depth from 3.5 to 10.7 meters, with the maximum depth of water level in summer being of the order of six meters.
Ground water in Karaikal is developed chiefly by means of dug wells or filter-point wells piercing blown sands and alluvium. A few bore-holes not exceeding 50 meters in depth drilled in the vicinity of Karaikal were reported to have been abandoned on account of the poor quality of water in the granular zones in the alluvium. However the data of a deep bore-hole put down at Karaikal in 1884 indicated that confined aquifers overlain by a thick bed of clay could be expected to occur below a depth of 90 meters in and around Karaikal which is expected to be a source of potential water supply, if tapped by tube-wells.
To the South and West of Muppattankudi and towards Mathur further West, sands are met with down to depths of 8 to 12 metres below surface. Wells tapping these sand yield water in plenty. About 1.6 km. South-East of Nedungadu, in the Western portion of the region, confined aquifers have been tapped by a tube-well. In a number of tube-well attempted down to depths of upto five metres only brackish water is reported to have been met with. A tube-well down to a depth of 61.7 m. near Akalanganni is said to yield brackish water.
Karaikal town gets its water by means of a battery of a shallow interconnected open wells and an infiltration gallery in the bed of Arasalar. A few villages between Akalanganni and Karaikal also get their water supply from this source. The town faces difficult water supply position during the months of April-June, when there is no flow in the Arasalar. Owing to the limited extent and thickness of sands in the bed of wells in Arasalar in the vicinity of the well site, attempts to increase the number of wells in Arasalar bed have been unsuccessful.
The Geological Survey of India, in a report (1965) had suggested to probe the bed of Nandalar to find out areas where sands may be sufficiently thick, so that wells or infiltration gallery could be constructed for augmenting water supply to Karaikal and other villages. The report had also suggested the drilling of a few exploratory bore-holes piercing the deeper aquifers in order formations so as to tap, if possible, ground water of good chemical quality by means of tube-wells in the North-Western portion of Karaikal region under proper technical supervision (Gazettiar ).
Surface and Ground Water Quality
The surface water in Karaikal region maintains a pH range around 8.44 - 8.77. The TDS is high in coastal areas mainly because of salt water ingression. Most of the areas in Karaikal district have high TDS (in some places ranging from 800 to 2000 mg/litre) and alkalinity ranges from 210-270mg/litre. The Brackish water aquaculture in Karaikal region considerably lowers the ground water quality. The ground water resource is of rather poor quality in Karaikal.