The South Pennar River is known as Thenpennaiyaru in Tamil and Dakshina Pinakini in Kannada. It is also referred as Ponnaiyar . The river originates from the South-Eastern side of the Chennakesava hills and the North-Western side of the Nandi Hills or Nandidurg in the Chikkaballapur district of Karnataka state. It flows for a distance of about 85 kilometres within Karnataka, to the north of Bangalore. Just before the interstate border, excess water from Bellandur and Vartur lakes in Bangalore flows into the river and then it flows towards south east and enters Tamil Nadu at a distance of 4 kilometres to the west of Pagalur (about 50 km north west of Bagalur village of Hosur Taluk in Krishnagirir District). It flows 400 kilometres (km) from its point of origin before joining the Bay of Bengal at Cuddalore district of Tamilnadu.
En route, its chief tributaries are the Chinnar (Markanda nadhi), Vaniyar and Pambaru rivers. It is the sole water source in Krishnagiri, Tiruvannamalai, Villupuram and Cuddalore districts.
The Chinnar (Markanda nadhi) flows due south from the Mysore Plateau through the valley of Tirtham and Veppanapalli and joins the South Pennar river.
The river Vaniyar originates and run completely in Shervaroyan Hills close to Yercaud in Tamil Nadu. It joins the Thenpennai River in Boongarrampatty Reserved Forest area.
The river Pambaru rises on the hill of Javadhu near Alangayam and from Thirupathur southwards it flows a course of remarkable straightness through Uthangarai and joins the South Pennar.
The Gadilam River, which starts in eastern part of Thirukoilur 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 Thenpennai and the Gadilam are connected by a river course called "the Malattar", which serves to carry the surplus water from Thenpennai to Gadilam.
Benefitting from South Pennar:
The Thenpennai River covers 110 km in Karnataka, 140 km in Krishnagiri and Dharmapuri, 35 km in Tiruvannamalai, 105 km in Villupuram and 40 km in Cuddalore districts. The river has a catchment area of 1,424 mi2. The river is dry for the most part of the year. Water flows during the monsoon season when it is fed by the southwest monsoon in catchment area and the northeast monsoon in Tamil Nadu. However this water flow raises the water table throughout the river basin and feeds numerous reservoirs/tanks.
The Thenpennai and its tributaries besides a number of lakes, tanks and ponds are supporting for irrigation and drinking water and other uses from its point of origin before joining the Bay of Bengal.
The Thenpennai River is the main source for irrigating over 38,000 acres in Krishnagiri district; 6250 acres in Dharmapuri district; 17,980 acres in Tiruvannamalai district and 25000 acres in Villupuram district (The district largely depend on ground water, lakes and tanks for irrigation). It is also the main source of drinking water to more than 100 villages along its route.
Thenpennai River systems, especially those closer to human settlements and industrial developments suffer from acute levels of pollution. River that flow through densely populated areas including towns and housing areas are often polluted with solid wastes.
Soil erosion caused by land development in the surrounding areas and untreated waste discharges from nearby factories further contribute to the high pollution levels. These toxic wastes not only destroy aquatic life but also surrounding vegetation, flora and fauna due to its highly acidic levels.
Thenpennai River which gives drinking water to Krishnagiri, Tiruvannamalai, Cuddalore and part of Villupuram districts is on the verge of ruin owing to dumping of Industrial and medical wastes, plastics and city garbage indiscriminate letting of domestic sewage water into the river.
Industries around Bellandur lake in Karnataka and in Hosur areas releases effluents directly into the water body.
Fertilizers used by farmers of Karnataka as well as Tamilnadu have made things worse. Very high levels of phosphate in the water.
In Kaveripattinam town, a four-km sub-channel on the right side of the river is being used to let off sewage water from houses and commercial establishments on the river banks. In many places walls of this channel are broken and the sewage water flows directly into the river.
This river is now looted for its rich availability of sand. As a result of extensive sand mining along the river, water now reaches the wells without being purified. Its bacterial content is, therefore, very high.
Many of the open wells in the adjacent villages of river banks are dried because of uncertain rainfalls and drought; they are used as dumping pits.
The Government attempts alone are not enough to protect the river and its environment, the community participation in water management is essential.