The main rivers of the district are the Noyyal and Amaravathi, the tributaries of Cauvery are flowing towards east. The Palar and Nallar river and other small rivers which flowing towards west.
The Noyyal, or the Noyyil, takes its rise in the Bolampatty Valley of the Veiliangiri hills, and comes to be called the Swami, until further south, it is joined by the Periyar. Its runs past Perur assuming another name as the “Kanchi Mahanadi”, then flows into Coimbatore town and flows, for a short distance, the boundary of the Coimbatore and Avanashi Taluks. Here it receives on the left the Vannathankaraipallam, a drainage course which has its sources in the north of Coimbatore town and, after flowing past Tiruppur it receives the Nallar stream on the left. In the remaining part of its course, it forms the boundary of the Kangayam and Erode taluks and after entering the Karur District, it joins the Cauvery. It is little more than a jungle stream being altogether dry for months in the year. At its sources it does not receive much supply from the south-west monsoon and is largely fed by petty affluents from the plains during the north-east monsoon. A Dam was constructed near Orathupalayam of Perundurai and Kangeyam Taluks boundary.
The Amaravathi rises in the Anjanad Valley in the Kerala State between the Anaimalai hills and the Palanis. Chinnar river originate from Anamalai hills joins with another river called Tenar of Palani hills, and form a Amaravathi river. It descends in a northerly direction and debouches into the plains near Kallapuram at the mouth of the Anjanad Valley in the Udumalpet Taluk. It then runs north-east and receives the Kudiriyar from the Dindigul District on the right at Kumaragam. Thereafter it flows into the Dindigul District to emerge again into the Dharapuram Taluk. Here, after passing the town of Dharapuram and receiving the Uppar on its left, it goes along a winding course, fed by a few small streams, and finally leaves the district and enters the Karur District and falls into the Cauvery at Kattalai in the Kulitalai Taluk. Fed by the south-west monsoon, it flows with some regularity from June to the end of August; then-it-falls to some extent in September, but rises again with the north-east monsoon till November, when it begins to fall once more until March at the end of which it is practically dry. Its banks are low and its water is fully utilised for irrigation of good quality along its entire course as a dam name Amaravathi was constructed near Kallapuram on the mouth of Anjanad Valley in Udumalai Taluk.
The Palar River rises from joining of five different rivers in the Varasathi malai, Kurumalai, Thenmalai and Picharimalai of Anaimalai Reserve Forest of Western Ghatt. The five rivers are Kanaaji River, Vanji River, Kottai River, Kurumalai River and Thoni River. The Kannaaji river and Vanji Rivers forms Tattan Kanuvai River and other three rivers joining together forms as Mungammalai Pallam. The Mungammalai Pallam and Thattan kanavai River joins near Panchalingam Hills forming Panchalingam river and passes through the Panchalingam Temple and Tirumurthi Temple and finally reaches plain from where it named as Palar. The Palar River flows in north-west direction through Tiruppur and Coimbatore Districts and confluences with Aliyar river near Ambarambalayam. Enroutes, large number of streams joins Palar river, the major one being “Nallar River” which joins Palar river near Devanurpudur village of Udumalpet Taluk. Tirumoorthy dam was constructed near Tirumoorthy Temple in the Palar river.
The Nallar River originates some where between Kokkanamalai and Varasathi Malai in Kurumalai and Boochakkattamparai forest settlement of Anamalai Reserve Forest in Western Ghat and runs Northern direction and cross the countour Canal near Puliapatti. These river traverse in the plains towards north-east for short distance and again turn in to north for some distance and finally confluence with Palar River near Devanurpudur.
CHINNAR RIVER :
The Chinnar River originates in the Annaimalai Hills below a grassy pass between the hills Kumarikal Malai (8,275 ft) and Kaladekatti Malai in Idukki District, Kerala. The 18 km long Chinnar river defines the East-West Tamil Nadu/Kerala state boundary along the northern edge of the Chinnar Wildlife Sanctuary and the southern edge of the Indira Gandhi Wildlife Sanctuary. Several adult Crocodiles were reported in the Chinnar River in 1992. The river is joined from the south by the Pambar River at Koottar just 2 km east of the road bridge (interstate check post). The western part of the Manjampatti Valley catchment basin, by the stream Ten Ar (Ten rivers) drains into the end of the Chinnar River and it become Amaravathy River.