Bhavani rises in the silent valley in Palghat ranges in the neighbouring state of Kerala, after receiving Siruvani, it flows into Coimbatore District where it gets reinforced by the Kundah River before entering Erode District in Gopichettipalaiyam. Bhavani is more or less a perennial river fed mostly by the South West monsoon. North East monsoon also supplements its water resources. This river runs for over hundred miles through Erode traversing through Bhavani and Gopichettipalaiyam Taluks (also spelt as Taluka). It feeds the Bhavanisagar reservoir, which takes an easterly course flowing through Gopichettipalaiyam, Satyamangalam and Bhavani Taluks, before it ultimately joins river Kaveri on the Salem borders.
Kaveri is among the most sacred rivers of India and is known as "the Dakshina Ganga" or "Ganga of the South". It flows through a length of 760-kms covering Karnataka And Tamil Nadu and its main tributaries are Bhavani, Noyil, Amaravati and Kollitam.
In Coorg district of Karnataka, Kaveri has its origin in Talakaveri at the height of 1,341 meters. The first dam built on this river is " Krishnaraj Sagar " at 19-km from Mysore where it meets with Hemawati and Laxmantirth rivers. After 25-km from Srirangapatnam it meets Kabini and Suvarnawati rivers and near Shivsamundaram, it falls from the height of 90 metres and creates many beautiful waterfalls and springs. At 64 kms from this place, it forms the border of Karnataka and Tamil Nadu. Here, it meets with Simsa and Akrawati rivers. In Tamil Nadu, it flows in east direction but from Hogenakkel waterfalls, it flows in south direction. At 45-km from Maitoor, it meets with its main assistant river Bhavani. When it enters into Tiruchirapalli District, it meets with Noyil and Amaravati rivers. Here it is the widest of whole of its path and hence, it is called "Akhand Kaveri". After Tirucharapalli, it divides into two branches. Upper branch is called 'Kaileroon' and falls in Bay of Bengal near Portonova. Southern branch is called 'Kaveri', which also falls in Bay of Bengal near Taranqubar.
Noyil River, a tributary of Kaveri is noted for its capricious nature. This is fed mostly by the Southwest monsoon but the Northeast monsoon brings rains and this very often results in floods. Inspite of its unpredictable character, the river helps to irrigate considerable areas in Palladam Taluk of Coimbatore District and Dharapuram Taluk of Erode.
Cheyyar, Thcnpennai, Ramandala Nagu, Thurinjalaru and Suganadhi are the important seasonal rivers flowing in Tiruvannamalai district. Cheyyar is a tributary of Palar, which originates in Kolar. River Cheyyar flows through Chengam Taluk of Tiruvannamalai district. It receives rain during the Northeast and Southwest monsoon periods. Cheyyar River passes through several villages of Chengam Taluk, and is the major source of irrigation. The Taluk has different types of soil, such as black, red loam and sandy loam. Major crops raised in the Taluk are paddy and groundnut. Magaral lies on the northern banks of Cheyyar River. Across the river lies the Kadambarkoyil temple.
Palar River rises in the Eastern Ghats near Coimbatore, runs through Vellore and Chingelput districts of Tamil Nadu and terminates into the Bay of Bengal near Caturangapattinam.
Palar River used to supply good drinking water to 30 towns on its banks and 50 villages surrounding it. The Palar river water was also used by the villagers to cultivate their land. Now, there are a number of tanneries on the banks of the River Palar. They let out the effluents in the Palar River. So, now the river water has been polluted and it is not useful for drinking or agricultural purposes. Due to pollution, the people are suffering from a number of diseases like asthma, skin disease and stomach ailment, etc. Thousands of acres of fertile land have become wasteland and it is not used for cultivation.
The river Tambaraparani (Now people call Tambaraparani as Thamirabarani) originates on the eastern slopes of Western Ghats in Tirunelveli district of Tamil Nadu. The origins of Tambarabarani and its tributaries are situated at the peaks called "Aduppukkal Mottai", "Agathimalai" and "Cherumunji Mottai", at an altitude of about +2,000m from the mean sea level. The Tambarabarani basin is situated between latitudes 8.21' N and 9.13' N and between longitudes 77.10' E. Vanatheertham waterfalls (40 m deep) is located close to the origin of the main river. This river joins the Papanasam Reservoir at its 16th km. The river has 4 tributaries called Peyar, Ullar, Karaiar and Pambar upstream of Papanasam Reservoir. The River Servalar, a main tributary of Tambarabarani joins the main river at a running distance of 22-km. Another tributary Manimuthar originates in the Agathimalai Ranges at an altitude of about +2,000 m above mean sea level. It joins the Tambarabarani at its 36th km near Ambasamudram. Gadana River joins at its 43rd km on the left.
The Gadana River has two tributaries namely Jambunadhi and Ramanadhi. There are six anicuts across Gadana and 7 across Ramanadhi. There is a reservoir across Gadana with a storage capacity of 352 m.cft. The Gadana River irrigates 3,887.09 hectares of wetlands. There is a reservoir of 152 m.cft. capacity across Ramanadhi. This river irrigates 2,023.47 hectares of wetlands. Pachaiyar, the next tributary joins Tambarabarani at its 61st km near Gopalasamudram. This tributary originates from the Kalakkadu reserve forests at an altitude of about 1,300 m above mean sea level. It has 12 anicuts across and irrigates 6,151.35 hectares of wet and dry lands. Chittar, a tributary of Tambarabarani joins it at its 73rd km, running almost parallel to Tambarabarani till its confluence. The river Tambarabarani, after the confluence of Chittar, travels another 23-km where it has the Srivaikundam anicut. From thereon, it runs eastwards for 30-km and enters the Gulf of Mannar near Palayakayal.
The Chittar has 5 tributaries, 3 sub tributaries and numerous small streams contributing the flow. The Chittar and its tributaries have their origin in Courtallam hills in Tenkasi and Shencottah Taluks of Tirunelveli District. The Chittar runs for about 80 kms before it confluences with Tambaraparani. The Chittar's first tributary is Ayindaruviar (River of Five Falls), which has an anicut and irrigates about 293.40 hectares of land. Hariharanadhi confluencing with Chittar has two sub tributaries called, the Gundar and Mottaiar. The Mottaiar has a reservoir and a pick up anicut feeding 141.64 hectares.The Gundar, which is also called "Karungalar" has 7 anicuts and a reservoir. They irrigate 465.39 hectares of land altogether. Mottaiar joins Gundar and Gundar joins Hariharanadhi. The Hariharanadhi itself has 7 anicuts and irrigates 445.10 hectares of land. Aludakanniar, another tributary to Chittar has 8 anicuts irrigating 827.47 hectares of land. Hanumanadhi is the next tributary to Chittar. It has a sub tributary called Karuppanadhi. There is a reservoir of 185 m.cft, capacity across Karuppanadhi besides 6 anicuts. These irrigate 3,844.59 hectares, the Hanumanadhi has 14 anicuts and irrigates 4,046.94 hectares and the last tributary to Chittar is Uppodai. Uppodai irrigates 445.16 hectares through two anicuts. The Chittar River itself has 17 anicuts irrigating 8,903.27 hectares of land.
The River Servalar, a main tributary of Tambarabarani joins the main river at a running distance of 22-km. The diversion weir marks the confluence of Servalar and Tambaraparani. A diversion weir was constructed just below the confluence of Servalar. The weir has a storage capacity of 49 M.cft. The Powerhouse, just below functions with a gross head of 91 m and a capacity 4 x 7 MW. The Servalar Reservoir is across Servalar River. This is also a Masonry Gravity Dam of 450 m long and 53 m high. The reservoir has a storage capacity of 1,225 Mcft. The Power House at the reservoir will have an installed capacity of 20 MW. The Papanasam and Servalar reservoirs are interconnected by, a tunnel of 10,886 feet long. The tailrace water from Papanasam Power House joins the main river Tambarabarani and it serves the wetlands on both sides enroute before it confluences with Gulf of Mannar. Many tributaries join the river course in the plains both on the right and left flanks.
Ponnaiyar River flows across the boundary between Cuddalore and Villupuram Taluks and joins with the Bay of Bengal about 3 miles north of Cuddalore. The Gadilam River, which starts in eastern part of Tirukkoyilur Taluk of Villupuram district flows through Cuddalore Taluk. In Cuddalore Taluk, Malattar joins it on the right and then it flows into the Bay of Bengal at a point, just north of Cuddalore. The Ponnaiyar and the Gadilam are connected by a river course called "the Malattar", which serves to carry the surplus water from Ponnaiyar to Gadilam.
Rising in the Varushanad Hills of western Tamil Nadu, Vaigai River initially flows northeast through the Kambam and Varushanad valleys. In its central it flows eastward into the Vaigai reservoir at Narasingapuram. Near Sholavandan it bends to the southeast, passing Madurai town on its course to its mouth on Palk Strait, which separates the southeast coast of India from Sri Lanka. The Vaigai River rarely floods and its chief tributaries are the Siruliar, Theniar, Varaha Nadi, and Mangalar. It flows through a length of 150 miles (240-km), generally southeast. The Vaigai River basin (indicating agricultural areas) in Tamil Nadu has an area of 7,000-sq-km where current (and projected) supplies of surface and groundwater are not deemed sufficient to meet current (and projected) needs. In 1985 a tunnel diverted waters from the Periyar River in Kerala under a contentious 999-year agreement between Kerala and Tamil Nadu. The western and northwestern parts of the basin receive heavy rainfall during the monsoons, with an average rainfall of 850mm over the basin. The land use is predominantly agricultural (consuming about 3,800 MCM of water annually), with paddy as the primary crop. There are significant water-sharing conflicts within agriculture itself, with the various agricultural areas competing for scarce water supplies.