Cauvery Basin basic information

Cauvery River Basin is located in between the longitudes 75⁰ 30’ and 79⁰ 45’ and north latitudes 10⁰ 5’ and 13⁰ 30’.  The Cauvery River Basin covers an area of 87,900 km2 and flows in Karnataka, Kerala and Tamil Nadu. The Cauvery basin is bounded on the West by the Western Ghats, on the east and south by the Eastern Ghats and on the north by the ridges separating it from the Tungabhadra and Pennar basins.

Land Use & Land Cover

Land use classification of the Cauvery River basin is given in Table

Land use and Land cover of Cauvery Basin

S. No	Description	Area (ha)
1	Geographical area	48,73,000
2	Forest	6,57,000
3	Area not available for cultivation	6,81,000
4	Cultivable area	30,22,000
5	Uncultivated cultivable area	8,93,000
6	Net area sown	21,29,000
7	Area sown more than once	4,44,000
8	Total cropped area	25,73,000
9	Net area Irrigated	9,96,000
10	Gross area Irrigated	12,82,000

(Source: Irrigation Commission Report)

Drainage

The Cauvery rises at Talakaveri on the Brahmigiri range of hills (12⁰25'N, 74⁰34'E) in the Western Ghats in the Coorg district of Mysore State, at an elevation of 1,341 m. above mean sea level.

In Tamil Nadu, the Cauvery continues to flow eastwards and forms the boundary between the Salem and Coimbatore districts. At Hoganekal falls, the river takes a southerly course and enters the Mettur reservoir, which was constructed in 1934. The river emerges from the Eastern Ghats below the Mettur reservoir and continues southwards. The Bhavani river joins it on the right bank about 45 km. below the Mettur reservoir and, thereafter, the river takes a more easterly course to enter the plains of Tamil Nadu, where it is joined on the right by two more tributaries, the Noyyal and the Amaravathi, before entering the Trichy district. Here the river widens with a sandy bed and flows in an easterly direction, as the ‘Akhanda Cauvery’.  Immediately below Trichy, the river splits into two branches, the northern branch being called the Coleroon, and the southern branch retaining the name of the parent river. The well-known Upper Anicut was constructed in 1836 at this point to facilitate diversion of the low supplies of the river into the Cauvery, which was the feeder channel for the old delta. It is here that the Cauvery delta begins. Some 16 km. below, the two rivers join again to form the Srirangam Island. The Grand Anicut is situated at the junction point below the island and forms the head of the great irrigation system in the Thanjavur district. Below the Grand Anicut, the southern or Cauvery branch further splits into two, one being called the Cauvery and the other, the Vennar. These channels are utilised as the main canals for the supply of irrigation water to the fields in the delta. The water is regulated at their heads by regulators. The branches, in turn, divide and sub-divide into innumerable smaller branches, which form a network all over the delta, distributing the Cauvery waters in the vast irrigation system. Some branches ultimately find their way to the sea while others peter out in the wide expanse of fields. The branch, which retains the name of the Cauvery throughout its course, enters the Bay of Bengal, as an insignificant stream at Kaveripatnam, about 13 km north of Tranquebar.

The northern branch, or the Coleroon, is the main flood carrier. After its bifurcation at the upper Anicut, it continues to flow in a north- easterly direction to enter the Bay of Bengal near Porto Novo.

The total length of the river from the head to its outfall into the sea is 800 km, of which about 320 km. are in Karnataka, 416 km in Tamil Nadu and the remaining length of 64 km forms the common boundary between the States of Mysore and Tamil Nadu.

Tributaries of Cauvery basin

The river Cauvery is the largest in Tamil Nadu and its major tributaries in the state are Bhavani, Noyyal and Amaravathi.  The Bhavani River is an important tributary of river Cauvery in its mid-reach. The National Water Development Agency of Ministry of Water Resources classified the entire Cauvery river basins into five sub-basins, with the Bhavani basin being one of the sub-basins.  The Bhavani sub-basin constitutes 7.58% area of the Cauvery basin.

Bhavani Sub Basin

The Bhavani sub basin lies between north latitudes 10º 56’33” and 11º 46’ 14”, and east longitudes 76º 24’ 41” and 77º 41’ 11”.  The average length of the basin area is 138 km and the average width is 57 km.  The basin elevation varies above the MSL from 166m in plains to 2634m in hills.  The total drainage area of the basin is 6154 Sq. km. 

The river Bhavani originate from the forests in the hill ranges in the neighborhood of Silent Valley in Kerala, and flows in the southeastern direction up to Mukkaliyar.  During its course a number of smaller streams of various orders and rapids join to the river.  Further to Mukkaliyar, it takes a northeastern course until its confluence with the river Moyar, a tributary originating in the Nilgiris.

Noyyal Sub Basin

The river Noyyal originates in the hills of Western Ghats and flows through Coimbatore, Erode and Karur districts. It has a catchment covering 3,510 km² falling in seven taluks namely, Coimbatore, Tirupur, Avinasi, Palladam, Karur, Erode and Dharapuram.  Out of 3510 km2 of Noyyal basin, 1752 km² is under cultivation which accounts for 49.9%; the rest of 1580, km² comes under barren, uncultivated lands, rocky strata, permanent pastures and fallow lands accounting for 45%.

The river Noyyal lies between north latitudes 10°54’00” and 11°19’03” and east longitude 76°39’30” and 77°05’25”.  High terrain ranging upto 1200m marks the western periphery of the river catchment.  In the central and eastern parts and towards the confluence of the river with the river Cauvery the terrain is plain and altitude falls to around 200m. 

Amaravathi Sub Basin

Amaravathi river is one of the main tributaries of river Cauvery which flows nearly about 192 Km from its origin. The river Amaravathi originates from Munar hills of Western Ghats in the Kerala state and enter into Annamalai hills in Coimbatore district of Tamil Nadu flows through Coimbatore, Erode and Karur districts and confluences with river Cauvery near Karur. Amaravathi river basin is bounded in the north by Noyyal sub basin of Cauvery basin, in the South by Vaigai basin, the West is bounded by the Kerala state and Parambikulam Aliyar basin, and in the east by Cauvery basin.  This river basin covers Coimbatore, Erode and Karur Districts

Noyyal water quality to be monitored online

To make monitoring of effluent discharge by dyeing units in Tirupur and Erode districts more effective, the Tamil Nadu Pollution Control Board (TNPCB) will have an online water quality monitoring system this year in the Noyyal river and Kalingarayan canal.

In the policy note tabled in the Assembly on Tuesday, Environment Minister B.V. Ramanaa said the process of procurement of instruments for continuous online monitoring of water quality in Noyyal river and Kalingarayan canal will be completed by May 31. TNPCB officials say there will be three online TDS (Totally Dissolved Solids) meters to measure the TDS levels. There will be a meter upstream, well before the effluent discharges begin, one right in the middle of the polluted river and canal and one downstream.

At present, the TNPCB officials are using hand-held devices to measure the TDS levels and the samples are tested in laboratories and only one test sample is taken every month, say sources. The online monitoring system that will be connected to the TNPCB website to make the readings public will give a real-time reading revealing patterns of discharge, sources add.

The instrument is expected to cost Rs 3 to 4 lakh a piece. Initially, the plan was to have 10 TDS meters in both but as it has not been tried before anywhere in the country, the government has decided to start with three. The data available will be for every minute and it could be made into a compilation of an hour's readings or as per required specifications. However, there is still the safety of the instruments that has to be addressed, officials say. The use of technology has been arrived at after farmers started complaining that there were indiscriminate discharges of effluents despite the court mandate of zero liquid discharge from dyeing units. “Once the online system is in place, we will be able to ascertain and zero in whenever there is any deviation from the normal pattern,” said a TNPCB official.