Utilization, area irrigated by completed major and medium projects in Cauvery basin.

Krishnarajasagar Dam

This is an existing major multipurpose project on Cauvery in Karnataka State. The latitude and longitude of the dam are 12⁰ 25' 30" N and 76⁰ 34' 30" E. It is located about 19.3 km from Mysore City near Kannambadi village, Srirangapatna Taluk, and district Mandya. The dam is situated below the confluence of the Cauvery River with two of its main tributaries, the Hemavathy and the Lakshmanathirtha. The catchment area of the dam is 10,619 km². The flow of the river at the site of the dam fluctuates from a normal high flood of 2,832 cumec during the monsoon season, to less than 3 cumec during the summer. The highest flood in the river which occurred in the year 1924 was 10,787 cumec.

KRS dam is a 2,620 m long gravity dam of stone masonry in surki mortar. The length of the dam at the top is 2621 m. There is no overflow spillway. The floods are disposed off through 152 sluice gates situated at different elevation in the body of the dam. Height of the dam above the bed level is 39.8 M. The reservoir formed by the dam has a gross and live storage capacity of 1,368.847 Mm³ and 1,244.21 Mm³ respectively. The water spread area of the reservoir at full reservoir level is 129 km². The reservoir fills during June to September period and supplies water during October to May period. The length of left bank canal is 45.92 km and the length of right bank canal is 32 km. The irrigation demand from the dam is 1,325 Mm³.

Salient features of KRS Project

The credit to construct this project goes to the eminent engineer of India, Dr. M. Visweswaraiah. In recognition to his services to the nation, Dr. Visweswaraiah’s birthday, September 15, is celebrated as engineer’s day in India. The project was commenced during the year 1911 and commissioned during 1932. The expenditure incurred on the project was Rs. 91 billion. An area of 10,785 ha of culturable land and 25 villages were submerged due to this project. The reservoir is named after the late Sri Krishna Raja Wadiyar in whose illustrious reign its construction was undertaken. KRS was constructed with the twin objectives:­

• To ensure a steady supply of water for generating Hydro-Electric Power at Sivasamudram.

• To supply water for irrigation of about 48,563 ha of land situated in the arid tracts of Mandya district.

Three canals take off from the dam. The main canal is the 44.8 km long left bank high level canal, named as Visweswaraiah canal after the well known engineer Dr. M. Visvesvaraiah. This canal has a capacity of 67.5 cumec and provides irrigation to 77,806 ha. The two low level canals have much smaller capacities. The 32 km long low level right bank canal, also known as Varuna canal, has a capacity of 7 cumec and provides irrigation to 1,534 ha. The low level left bank canal is 21 km long, has a capacity of 1.42 cumec and irrigation potential of 151 ha. The dam also provides flood control.

In addition to the main benefit of providing reservoir backed assured irrigation to a large area, a notable feature associated with KRS is the Vrindavan gardens. This is an exquisite garden located just below the KRS dam, and has a beautiful biological park, and a number of fountains run from the hydraulic head generated by the dam. The KRS dam supplies water for the upkeep of the garden which is a major tourist attraction of South India.

Mettur dam (Stanley Reservoir)

The flow in Cauvery is mainly dependent on the south-west monsoon which influences large parts of its upstream catchment in Karnataka and Kerala, in the months of July and August. It was seen that the flow in the river after the south- west monsoon receded, was not sufficient to support the agriculture in the Cauvery delta. The north east monsoon was less dependable and failed frequently, with the result that the delta irrigation suffered badly, often just at the time when the crops were in the maturing stage.

Mettur dam is a remarkable project. Situated at 11°49' N latitude, it is located at 52 km from Salem, in Salem District, Tamil Nadu, 270 km downstream of the KRS and just downstream of the Karnataka- Tamil Nadu border where the river emerges from the Eastern Ghats. Situated at an elevation of 243 m, it is a 85 m long masonry dam and a 1,615 m long earth dam section, the maximum height of the dam being 70.4 m. Rising above the Cauvery River bed, the dam is constructed across two hills of the Eastern Ghats. Mettur reservoir has catchment area of 42,217 km², a live storage capacity of 2.65 BCM. At FRL 241 m, the water spread area is 153.5 sq. km and its MDDL is at 219 m.

In the present form, Mettur Reservoir was formulated by Col. Ellis in 1910. Construction began in July 1925 and was completed by 1934. The Mettur Reservoir is also called Stanley reservoir; it got this name after Sir George Frederick Stanley, the then Governor of Madras, who inaugurated the project. At the time of its construction, Mettur was the highest masonry dam in Asia and the largest in the world. It was planned to store the high flows during the south-west monsoon and distribute them evenly throughout the irrigation period, thus firming up the irrigation provided by Grand anicut canals. It is a landmark project that has helped stabilize irrigation in the Cauvery delta area and has yielded consistent benefits for the past 75 years. This project has helped stabilize existing irrigation in 1.665 M-ha of area and has extended irrigation to 121,810 ha of new area. Constructed primarily to stabilize irrigation in Thanjavur delta, the dam caters to about one third of the irrigated area of Tamil Nadu besides generating hydroelectric power of 200 MW (4 units of 50 MW each). Stanley is the largest reservoir in Tamil Nadu.

In the reservoir, the highest and lowest water temperatures recorded are 32°C (in May) and 24.2°C in (January), respectively. Dissolved oxygen in the surface layer in most of the months is above 4 mg/1 with the maximum supersaturated conditions at the surface are accompanied by a depletion of oxygen in the hypolimnion. The water is alkaline, the pH values range between 7.5 to 8.8. Total hardness as CaCO₃ varies in a range of 86–128 mg/l suggesting the lake as a hard water one.

Even during the winter season, air temperature in this part of the country does not drop below 15 °C, keeping the water relatively warm. With the onset of summer, when the top layer warms up, there is no cool water below to offer any thermal resistance. Moreover, the release of cooler water from the bottom layer through the outlets of the dam removes any disparity in temperature between the top and bottom layers.

Lower Mettur Power Houses I/II/III/IV: In this system, there are 4 power houses, namely Lower Mettur Power House I, II, III, and Lower Mettur Power House IV. The power house I is located at Chekkanur Reservoir, 10 km downstream from Mettur dam. Power house II is located at Nerunjipettai Reservoir, 20 km downstream from Mettur dam. Power house III is located at Koneripatti Reservoir, 16 km down stream from Bhavani dam, and power house IV is located at Urachikottar Reservoir, 5 km downstream from Bhavani dam. These power houses are located on Cauvery River in Erode District, Tamil Nadu. The lengths of the dams are 948m, 1,478 m, 710 m and 1,085 m respectively. All the four power houses have 2 units of 15 MW each, producing a firm power of 46 MW.

Grand Anicut

An anicut (a kind of small barrage) known as the Grand Anicut was constructed across Cauvery River by the kings of Chola dynasty some 2,000 years ago, mainly to provide irrigation to large areas in Thanjavur district. With some minor changes, the Grand anicut is still in use and is one of the oldest in-use irrigation structures in the world that have been successfully serving their purposes; this one meeting the requirements of Cauvery delta area in Tamil Nadu. The Grand Anicut is located downstream of Mettur reservoir.  The irrigation demand from the anicut is 9,670 Mm³.

Nugu Reservoir

This reservoir is located near Beerwal village, H.D. Kote Taluk, Mysore District in Kabini sub-basin. The longitude of the dam is 76º 27' 00" and the latitude is 11º 58' 15". At the dam site, the catchment area is 984 sq. km. Nugu is an earthen dam on right side with central masonry spillway.

Salient features of Nugu Reservoir Project

Kundah I

Kundah I hydropower project is located at Avalanchi and Emerald masonry gravity dam, on Avalanchi and Emerald streams, 32 km from Udhagamandalam, in Nilgiris District, Tamil Nadu. The catchment area at the dam is 58.5 km². The height and length of the dam is 57 m and 366 m respectively. At FRL 1,985.7 m, the reservoir has a live storage capacity of 154 MCM; the MDDL of the dam is at 1,943.1 m. Mean annual inflow to the reservoir is 108.2 MCM. The powerhouse has 3 units of 20 MW each to produce a firm power of 27.5 MW.

Kundah II

Kundah II hydropower project is located at Kundah Palam gravity dam constructed across Kundah River, 52 km from Udhagamandalam, in Nilgiris District, Tamil Nadu. The catchment area at this 32 m high dam is 113.96 km². The reservoir has a live storage capacity of 0.849 MCM; its FRL is at 1,624.6 m and the MDDL is at 1,609.34 m. Five units of 35 MW each have been installed at the powerhouse to produce a firm power of 63.5 MW.

Kundah III

Kundah III hydropower project is located at Pegumbahallah Forebay dam and Nirallapallam diversion weir, on Pegumbahallah Nirallapallam River, 77 km from Coimbatore, in Nilgiris District, Tamil Nadu. The catchment area at the Pegumbahallah dam is 41.44 km². The height of the Pegumbahallah dam is 55.5 m. The Pegumbahallah reservoir has a live storage capacity of 0.679 MCM at FRL 869 m; the MDDL is at 835 m. Power is generated by 3 units of 60 MW each yielding a firm power of 37 MW.

Kundah IV

Kundah IV hydropower project is located on Pillur dam on Bhavani River, 85 km from Coimbatore, in Nilgiris District, Tamil Nadu. The 88 m high dam has a catchment area of 1,191 km²; the dam is 357 m long and the mean annual flow to the dam is 685 MCM. The reservoir has a live storage capacity of 28 MCM at FRL 427 m and the MDDL is at 396 m. The power house has 2 units of 50 MW each. It has a firm power of 10 MW.

Harangi Dam

The Harangi dam is located in the Upper Cauvery sub-basin near Hudgur village in Somwarpet Taluk of District Coorg. The latitude of the dam is 12º 29' 30" N and longitude is 75º 54' 20" E. At the dam site, the catchment area is 419.58 sq. km. Harangi is a masonry dam with central spillway and non-overflow section and there are earthen dams on either flank. Length of the dam is 845.8 m. Table 15.9 gives the salient features of the Harangi dam.

Salient features of Harangi dam

Hemavathi Reservoir

The Hemavathi reservoir is located on Hemavathi River near Gorur village in Taluk and district Hassan in the Upper Cauvery sub-basin.  The latitude of the dam is 12⁰ 45' 0" N and the longitude is 76⁰ 03' 0" E. At the dam site, the catchment area is 2810 sq. km. It is a masonry dam with central spillway and earthen flanks on either bank. 

Salient features of the Hemavathi project

Kabini Reservoir Project

The Kabini dam was constructed on the river with the same name in the Kabini sub-basin near village Beechanahally in Mysore district. The latitude and longitude of the dam are 11^o 50' 30" N and 76^o 20' 17" E.  At the dam site, catchment area is 2141.90 sq. km.  

Salient features of the Kabini Reservoir Project