"The Drainage Systems of Tamil Nadu All river systems of the state flow eastward from the Western Ghats and are rain fed. The Palar, the Ponnaiyar and the Cheyyar are three important river systems in the north. None of them is perennial. A river which cuts across the centre of the state is the Cauvery. Fed by both monsoons, it is practically perennial, although in recent years this has become drier mainly due to the dams in Karnataka. There is a long standing water dispute, waiting to be redressed, between the state of Tamil Nadu and Karnataka. Yet, along with its tributaries, the Bhavani and the Amaravathi, it is the most important source of canal irrigation. In the south of the Cauvery, the state contains three important rivers, namely, the Vaippar, the Vaigai and the Tamiravaruni. Of these, Tamiravaruni is perennial and a source of canal irrigation. Besides these, there are several other smaller and less important rivers in the state. Some important tributaries of various rivers are, Upper Cauvery, Kabini, Suvarnavathi, Middle Cauvery, Chinnar, Noyil, Thirumanimuthar, Peyar, Vellar, Karayar, Pambar, Servalar, Manimuthar, Gadananadhi, Pachayar, Nichabanadhi, Uppodai, Kalingalur, Arjuna Nadhi, Nagariar, Kousiga Nadhi, Deviar, Senkottaiar, Kayalkudiar, Vallampatti Odai, Sevalaperiyar, Uppathur, Sindapalli. and Chittar.Source: SRTM, Glovis for Relief and Administrative Atlas of Tamil Nadu for DrainageIrrigation Canals, tanks and wells are the main sources of irrigation for farmers of the state. As of 2005-2006, the state had 2395 canals with a length of 9,747 km, 40,319 tanks, 670 ordinary government wells, 1,620,705 ordinary private wells and 290,611 tube wells. Irrigation increases the productivity of the land. The main modes of irrigation in Tamil Nadu are rivers, tanks and wells.Streams and spring channels are other sources of minor importance. Thanjavur, Coimbatore, Erode, Tiruchirappalli, Cuddalore, Viluppuram, Madurai are the districts accounting for the irrigation facilities.These are the districts watered by major rivers such as the Cauvery, Parambikulam-Aliyar, Palar, Pennaiyar and Vaigai. The most important river basin in Tamil Nadu is the Cauvery basin. Extending over an area of 88,000 square kilometres, it is shared by Tamil Nadu, Karnataka and Kerala. Since independence, numbers of irrigational projects have been completed.The important among them are lower Bhavani, Parambikulam-Aliyar, Amaravathi, Krishnagiri, Sathanur, Vaigai, Mettur, etc. Modernization of existing Periyar Vaigai System, Palar Basin System and Parambikulam-Aliyar System, besides the minor system in Vellar, Pennayar, Araniyar Amaravathi, Chithar basins comprising of six lakh acres of existing ayacut in Tamil Nadu, have been benefited by implementing the 'System Improvement and Farmers Turnover Projects' executed with the assistance from World Bank. The World Bank has also approved 2,547 crore for the Modernization of agriculture and Water Bodies Restoration Management Project. The Project covers about 6.17 lakh ha, in 63 selected sub-basins throughout the state.Nine irrigation projects, which were once just started and going on at a slow pace, have been speeded up with adequate fund and guidance for early completion. The major irrigation system covering one-third of irrigated land in Tamil Nadu, namely tank irrigation system has been given due regard for development under Water Reserve Conservation Programme (WRCP)and 620 tanks maintained by Public Works Department falling under Palar, Vaigai and Tamaraparani Basins have been taken up for rehabilitation and improvement. This project is nearing completion to the maximum satisfaction of the farmers. This state has become the pioneer state to implement the system of 'River basin management' by an individual body consisting of officials and farmers, besides various representatives of the basin. Surface irrigation potential has largely been exhausted. Area under canal irrigation has remained almost stagnant since sixties and that is about 8.5 lakhs hectares. Modernisation of several of the canal systems has been taken up under the National Water Management Project and the World Bank funded Water Resources Consolidation Project. The efficiency of many of the canal systems has declined due to seepage and silting. The efficiency of canal irrigation can be improved through command area development, participatory irrigation management, conjunctive use of surface and ground water, and reduction in the wastage of water due to over irrigation (Tamil Nadu Development Report, 2005, Planning Commission, Government of India)."