Idamalayar Dam is a multipurpose concrete

gravity dam A gravity dam is a dam constructed from concrete or stone masonry and designed to hold back water by using only the weight of the material and its resistance against the foundation. Gravity dams are designed so that each section of the dam is ...

located at Ennakkal between Ayyampuzha and

Bhoothathankettu Bhoothathankettu is a dam and tourist spot in Ernakulam district in Kerala. It is situated outside the village of Pindimana, about 10 km away from the town of Kothamangalam and 50 km away from the main city of Kochi. The origin ...

Ernakulam district Ernakulam (; ISO: ''Eṟaṇākuḷaṁ'') is one of the List of districts of Kerala, 14 districts in the States and union territories of India, Indian state of Kerala, and takes its name from the Ernakulam, eponymous city division in Kochi. ...

Kerala Kerala ( , ) is a States and union territories of India, state on the Malabar Coast of India. It was formed on 1 November 1956, following the passage of the States Reorganisation Act, by combining Malayalam-speaking regions of the erstwhile ...

on the Idamalayar, a tributary of the Periyar River in

South India South India, also known as Southern India or Peninsular India, is the southern part of the Deccan Peninsula in India encompassing the states of Andhra Pradesh, Karnataka, Kerala, Tamil Nadu and Telangana as well as the union territories of ...

. The dam however extends east as far as

Malakkappara Malakkappara or Malakhappara is a small hill station in Thrissur district of the state of Kerala, India. This place is situated on the border between Kerala and Tamil Nadu. Etymology The place gets its name from the Malayalam word ''Malakha-P ...

. Completed in 1985, with a length of and a height of , the dam created a multipurpose

reservoir A reservoir (; ) is an enlarged lake behind a dam, usually built to water storage, store fresh water, often doubling for hydroelectric power generation. Reservoirs are created by controlling a watercourse that drains an existing body of wa ...

covering in the scenic hills of the

Anamalai The Anamala or Anaimalai, also known as the Elephant Mountains, are a range of mountains in the southern Western Ghats of central Kerala (Idukki district, Ernakulam district, Palakkad district, Thrissur district) and span the border of wester ...

s. The reservoir storage is utilized by a

hydroelectric power station Hydroelectricity, or hydroelectric power, is electricity generated from hydropower (water power). Hydropower supplies 15% of the world's electricity, almost 4,210 TWh in 2023, which is more than all other renewable sources combined and also mo ...

which has an

installed capacity Nameplate capacity, also known as the rated capacity, nominal capacity, installed capacity, maximum effect or gross capacity,MW with two units of 37.5 MW capacity, producing an annual energy output of 380

GW·h A kilowatt-hour (unit symbol: kW⋅h or kW h; commonly written as kWh) is a non-SI unit of energy equal to 3.6 megajoules (MJ) in SI units, which is the energy delivered by one kilowatt of power for one hour. Kilowatt-hours are a common b ...

. The large reservoir created by the Idamalayar Dam is operated by the

Kerala State Electricity Board Kerala State Electricity Board (KSEB) is an Indian public sector undertaking under the Government of Kerala that generates, transmits and distributes electricity in the state. Established in 1957, the agency comes under the authority of the Po ...

to augment its peak power generation requirements. The dam will benefit the Idamalayar

Irrigation Irrigation (also referred to as watering of plants) is the practice of applying controlled amounts of water to land to help grow crops, landscape plants, and lawns. Irrigation has been a key aspect of agriculture for over 5,000 years and has bee ...

Development Project by diverting water released from the tail race channel of the Idamalayar power station.

Geography

The Idamalayar Dam is located on the Idamalayar River, a tributary of the Periyar River in Kerala.

Edamalayar Edamalayar or Idamalayar is one of the major tributaries of the Periyar River, the longest river in Kerala, South India. TheIdamalayar Dam is built on this river. It originates in the Anamalais of Kerala's Ernakulam district, and flows into T ...

originates in the

Anamala Hills The Anamala or Anaimalai, also known as the Elephant Mountains, are a range of mountains in the southern Western Ghats of central Kerala (Idukki district, Ernakulam district, Palakkad district, Thrissur district) and span the border of wester ...

itself at elevation of . The river is a perennial source draining a catchment area of with a topography of high relief. The catchment receives annual rainfall of , 90% of which occurs during the

monsoon A monsoon () is traditionally a seasonal reversing wind accompanied by corresponding changes in precipitation but is now used to describe seasonal changes in Atmosphere of Earth, atmospheric circulation and precipitation associated with annu ...

months of June to September. The dam is located from Ernakulam in Ernakulam district and from the

dam (literal meaning in

Malayalam language Malayalam (; , ) is a Dravidian language spoken in the Indian state of Kerala and the union territories of Lakshadweep and Puducherry ( Mahé district) by the Malayali people. It is one of 22 scheduled languages of India. Malayalam wa ...

: "monster dam") on the Periyar River, which takes its name from local myths attributing its construction to demons who built it with the intention of submerging Thrikkariyoor temple. IndamalayarReservoir View

, , , , , , , , , , , , , , , , ,

Water resources

Based on detailed hydrological analysis, with observed data supplemented by rainfall-runoff correlation and prediction of low flows during dry months, the mean annual runoff was estimated as about 1,207 million cubic meters (million cubic metres) and that at 95% availability as 730 million cubic metres. Therefore, the live storage in the reservoir was fixed at 1,032.3 million cubic metres. However, subsequent to the commissioning of the project in 1987, availability of the flows was reassessed. It was noted that flows reduced to 1,178 million cubic metres in dry season and reached 4,361 million cubic metres during the monsoon. The total annual flow was assessed as 5,539 million cubic metres. As irrigation requirements are not critical during monsoon season the assessment of dry weather flows is relevant for irrigation. Further, Idamalayar storage is being supplemented from diversion of flows from the Peringalkuthu Reservoir during the monsoon season through the Vachumaram diversion canal constructed during 1997. The water stored in the reservoir is used for energy generation during the monsoon season by adopting a suitable reservoir operational schedule so that the water diverted from the diversion canal is not spilled out.

Structural details

The dam built across the Idamalayar River is a gravity concrete structure with a total height of above the deepest foundation level with a length of at the crest level. The full reservoir level is elevation and the minimum draw down level (MDDL) is . The dam has created a reservoir with a water spread of . The reservoir has a gross storage capacity of 1,089.0 million cubic metres of which the effective storage is 1,017.8 million cubic metres. The spillway has been designed to pass a design flood discharge of . The storage in the reservoir created behind the high concrete gravity dam is utilized for power generation by diversion through a water conductor system comprising a long power tunnel, surge shaft and two lines of penstocks connected to the turbines installed in a surface power station for generation of 75 MW of power with two units of 37.5 MW capacity each. Instrumentation is provided in the Idamalayar Dam and the observations carried out are analysed regularly to monitor the safety of the structure. However, a rehabilitation project envisaging improving the safety and operational performance of selected structures such as dams, barrages and regulators, which covers 19 projects under the Irrigation Department and 12 projects of the Kerala State Electricity Board, has been approved under the

World Bank The World Bank is an international financial institution that provides loans and Grant (money), grants to the governments of Least developed countries, low- and Developing country, middle-income countries for the purposes of economic development ...

funded "Dam Rehabilitation and Improvement Project (DRIP)" to be implemented from January 2011. Idamalayar Dam is one of the projects included in this programme. However, the rehabilitation work on this dam is proposed to be taken up in the second stage.

Power Generation

Idamalayar project is a low head Hydro Electric Scheme located in Ernakulam District. The power house is situated downstreams of the dam. Installed capacity of the Project is 75 MW. It is in the fifth position in Kerala in terms of Installed capacity. There is a power tunnel of length from where 2 penstock pipes takes the water to the power house. Two generators of 37.5 MW capacity produce the electricity. The units were commissioned in 1987 February. They generate 380 Million Units of power annually. There are two feeders from this Power house. First one is to

Chalakudy Chalakudy () is a municipal town situated on the banks of Chalakudy River in Thrissur district of the Kerala state in India. It is the headquarters of Chalakudy taluk. It is the base camp for travellers to Athirappilly Falls and Vazhachal Falls ...

and to Madakkathara from there and the second one is to Malayattur, perumbavur and joins the power grid in

Kalamassery Kalamassery () is a major industrial region in the city of Kochi in the state of Kerala, India. It is located around northeast of the city centre. Kalamassery is a major hub for industrial and Information Technology, IT activities in Kochi. In ...

Irrigation benefits

Irrigation benefits from the water stored in the Idamalayar Reservoir are proposed by utilizing the tail-race water released from the Idamalayar Power house. For this purpose, the project titled "The Idamalayar Irrigation Project" is under implementation. Under this project, the tail race discharge from the Idamalayar powerhouse is picked up at the barrage constructed across the Periyar River at Bhoothathankettu and diverted through a canal system on the right bank of the barrage. The irrigation benefits envisaged covers an area of of wet and dry agricultural lands, out of which the cultivable command area is . The project is under implementation since 1981. The cost of the project was initially Rs 18.5 crores (about US$411.11 million), which as per latest reports of 2007 is stated to be Rs. 539.50 crores (US$1198.9 million). According to the Annual Plan 2010–2011 of the State Government, substantial work of the main canal, the low level canal and the link canal still needs to be completed to derive full planned benefits of irrigation. Apart from power and irrigation benefits, the project situated in scenic forest area also provides recreational benefits of boating in the reservoir, bird watching and trekking.

Construction delays

The Idamalayar Dam project was started in 1970 and completed after 17 years. In an analysis carried out in 2001 on the reasons for the delay in completion of Hydropower Projects resulting in immense cost overruns in Kerala, it was noted that the Idamalayar project could be commissioned only in 1987 with a time overrun of 9 years and consequent cost overrun of 285% resulting in a capital cost of Rs 2.81 per kWh of generation. While technical reasons for the delays were fully documented, the delay highlighted, however, was attributed to the "irrational behaviour of the organized militant labour". A High Level Committee set up by the

Government of Kerala The Government of Kerala (abbreviated as GoK), also known as the Kerala Government, is the administrative body responsible for governing the Indian States and territories of India, state of Kerala. The government is led by a chief minister, who ...

, which examined this issue, observed that the Idamalayar Dam project has been the "victim of recurring and long inertial periods of labour unrest". There was also controversy over the contract awards. The government appointed Justice K. Sukumaran to inquire into allegations related to the Idamalayar and

Kallada Kallada is a village in Kollam district of the Indian state of Kerala. Maharaja Marthanda Varma of the kingdom of Travancore was born there. The Kallada River The Kallada River is the longest river in Kollam District, Kerala, India. The river ...

dam construction contracts. Based on his report, Minister R. Balakrishna Pillai and others were prosecuted by a Special Court. The Kerala high court later acquitted them, but in February 2011 the

Supreme Court of India The Supreme Court of India is the supreme judiciary of India, judicial authority and the supreme court, highest court of the Republic of India. It is the final Appellate court, court of appeal for all civil and criminal cases in India. It also ...

sentenced R. Balakrishna Pillai and two others to a year in prison for abusing their positions when awarding the contracts.

Birds

In the reservoir area of the Idamalayar Dam, several species of birds have been reported. The reservoir and surrounding areas are very rich in bamboo. The birds found are:

heart-spotted woodpecker The heart-spotted woodpecker (''Hemicircus canente'') is a species of bird in the Picidae, woodpecker family. It has a contrasting black and white plumage, a distinctively stubby body and a large wedge-shaped head making it easy to identify while ...

common flameback The common flameback (''Dinopium javanense''), also referred to as the common goldenback, is a small (28–30 cm), three-toed woodpecker in the family Woodpecker, Picidae, found throughout South Asia, South and Southeast Asia.Pittie, Aasheesh ...

, black rumped flameback,

greater flameback The greater flameback (''Chrysocolaptes guttacristatus''), also known as the greater goldenback or large golden-backed woodpecker, is a woodpecker species. It occurs widely in the northern Indian subcontinent, eastwards to southern China, the Mal ...

, crimson-fronted barbet,

Malabar grey hornbill The Malabar gray hornbill (''Ocyceros griseus'') is a hornbill endemic to the Western Ghats and associated hills of southern India. They have a large beak but lack the casque that is prominent in some other hornbill species. They are found mai ...

, Malabar trogon,

dollarbird The Oriental dollarbird (''Eurystomus orientalis'') is a bird of the roller family, so named because of the distinctive pale blue or white, coin-shaped spots on its wings. It can be found from Australia to Korea, Japan and India. Taxonomy The O ...

Oriental dwarf kingfisher The black-backed dwarf kingfisher (''Ceyx erithaca''), also known as the three-toed kingfisher, is a pocket-sized bird in the Family (biology), family Alcedinidae. It was formerly considered as conspecific with the rufous-backed dwarf kingfish ...

stork-billed kingfisher The stork-billed kingfisher (''Pelargopsis capensis''), is a tree kingfisher which is widely but sparsely distributed in the tropical Indian subcontinent and Southeast Asia, from India to Indonesia. These kingfishers are large and have a heavy bi ...

, common hawk cuckoo,

plum-headed parakeet The plum-headed parakeet (''Psittacula cyanocephala'') is a species of parakeet in the family Psittacidae. It is endemic to the Indian Subcontinent and was once thought to be conspecific with the blossom-headed parakeet (''P. roseata'') before b ...

, Malabar parakeet,

white-rumped needletail The white-rumped spinetail or white-rumped needletail (''Zoonavena sylvatica'') is a species of swift found in the forests of Bangladesh, India (the Western Ghats) and Nepal. It is often seen over waterbodies in the middle of forest. It can rese ...

brown-backed needletail The brown-backed needletail (''Hirundapus giganteus''), or brown needletail, is a large swift. These birds have very short legs which they use only mainly for clinging to vertical surfaces. They never settle voluntarily on the ground and spend m ...

jungle owlet The jungle owlet (''Glaucidium radiatum'') or barred jungle owlet is native to the Indian Subcontinent. The species is often found singly, in pairs or small groups, and they are usually detected by their calls at dawn and dusk. There are two subs ...

green imperial pigeon The green imperial pigeon (''Ducula aenea'') is a large forest pigeon. The large range extends from Nepal, southern India and Sri Lanka eastwards to southern China, Indonesia and the Philippines. Taxonomy In 1760 the French zoologist Mathurin Ja ...

emerald dove The emerald dove or common emerald dove (''Chalcophaps indica''), also called Asian emerald dove and grey-capped emerald dove, is a widespread resident breeding Columbidae, pigeon native to the tropical and subtropical parts of the Indian Subcon ...

grey-fronted green pigeon The grey-fronted green pigeon (''Treron affinis'') is a pigeon in the genus ''Treron''. It is found in the forests of the Western Ghats in India. Many authorities have split the species from the pompadour green pigeon complex. Description The m ...

river tern The River Tern (also historically known as the Tearne) is a river in Shropshire, England. It rises north-east of Market Drayton in the north of the county. The source of the Tern is considered to be the lake in the grounds of Maer Hall, Staff ...

brahminy kite The brahminy kite (''Haliastur indus''), also known as the red-backed sea-eagle in Australia, is a medium-sized bird of prey in the family Accipitridae, which also includes many other diurnal Bird of prey, raptors, such as eagles, buzzards, and h ...

hornbill Hornbills are birds found in tropical and subtropical Africa, Asia and Melanesia of the family Bucerotidae. They are characterized by a long, down-curved bill which is frequently brightly coloured and sometimes has a horny casque on the upper ...

grey-headed fish eagle The grey-headed fish eagle (''Icthyophaga ichthyaetus'') is a fish-eating bird of prey from Southeast Asia. It is a large stocky raptor with adults having dark brown upper body, grey head and lighter underbelly and white legs. Juveniles are paler ...

black eagle The black eagle (''Ictinaetus malaiensis'') is a bird of prey. Like all eagles, it is in the family Accipitridae, and is the only member of the genus ''Ictinaetus''. They soar over forests in the hilly regions of tropical and subtropical South a ...

, Oriental honey buzzard,

rufous-bellied hawk-eagle The rufous-bellied eagle or rufous-bellied hawk-eagle (''Lophotriorchis kienerii'') is a bird of prey in the Family (biology), family Accipitridae that is found in the forested regions of tropical Asia. Relatively small for eagles and contrasting ...

little heron The little heron (''Butorides atricapilla'') is a small heron, about 44 cm tall. It is mostly sedentary and frequents both fresh and salt water habitats. It is found in the Old World tropics from west Africa to Japan and Australia. The litt ...

Asian openbill The Asian openbill or Asian openbill stork (''Anastomus oscitans'') is a large wading bird in the stork family Ciconiidae. This distinctive stork is found mainly in the Indian subcontinent and Southeast Asia. It is greyish or white with glossy ...

, fairy bluebird,

small minivet The small minivet (''Pericrocotus cinnamomeus'') is a small passerine bird. This minivet is found in tropical southern Asia from the Indian subcontinent east to Indonesia Indonesia, officially the Republic of Indonesia, is a country in So ...

bar-winged flycatcher-shrike The bar-winged flycatcher-shrike (''Hemipus picatus'') is a small passerine bird usually placed in the Vangidae. It is found in the forests of tropical southern Asia from the Himalayas and hills of southern India to Indonesia. Mainly insectivorou ...

black-naped monarch The black-naped monarch or black-naped blue flycatcher (''Hypothymis azurea'') is a passerine bird belonging to the family of monarch flycatchers found in southern and south-eastern Asia. They are sexual dimorphism, sexually dimorphic, with the ...

Asian paradise flycatcher In 2015, the Asian paradise flycatcher was split into the following three species: * Indian paradise flycatcher The Indian paradise flycatcher (''Terpsiphone paradisi'') is a medium-sized passerine bird native to Asia, where it is widely distrib ...

Malabar whistling thrush The Malabar whistling thrush (''Myophonus horsfieldii'') is a whistling thrush in the family ''Muscicapidae''. The bird has been called ''whistling schoolboy'' for the whistling calls that they make at dawn that have a very human quality. Th ...

, rusty-tailed flycatcher, white-bellied blue-flycatcher,

Indian blue robin The Indian blue robin (''Larvivora brunnea'') is a small bird found in the Indian Subcontinent. Formerly considered a thrush, it is now considered one of the Old World flycatchers in the family Muscicapidae. It was earlier also called the India ...

chestnut-tailed starling The chestnut-tailed starling (''Sturnia malabarica''), also called grey-headed starling and grey-headed myna is a member of the starling family. It is a resident or partially migratory species found in wooded habitats in India and Southeast Asia. ...

, velvet-fronted nuthatch,

great tit The great tit (''Parus major'') is a small passerine bird in the tit family Paridae. It is a widespread and common species throughout Europe, the Middle East, Central Asia and east across the Palearctic to the Amur River, south to parts of No ...

, dusky crag martin,

red-rumped swallow The European red-rumped swallow (''Cecropis rufula'') is a small passerine bird in the swallow family Hirundinidae. It breeds in open hilly country of southern Europe and north Africa east to Iran, Pakistan and northwest India. During winter it m ...

Asian koel The Asian koel (''Eudynamys scolopaceus'') is a member of the cuckoo family of birds, the Cuculidae. It is found in the Indian Subcontinent, Pakistan, China, and Southeast Asia. It forms a superspecies with the closely related black-billed koels ...

yellow-browed bulbul The yellow-browed bulbul (''Acritillas indica''), or golden-browed bulbul, is a species of songbird in the bulbul family, Pycnonotidae. It is found in the forests of southern India and Sri Lanka. The yellow-browed bulbul is mainly yellow on the ...

, Wayanad laughingthrush, dark-fronted babbler,

rufous babbler The rufous babbler (''Argya subrufa'') is an endemic species of bird found in the Western Ghats of southern India of the family Leiothrichidae It is dark brown and long tailed, and is usually seen foraging in noisy groups along open hillsides ...

Nilgiri pipit The Nilgiri pipit (''Anthus nilghiriensis'') is a distinctive species of pipit that is endemic to the high altitude hills of southern India. Richer brown in colour than other pipits in the region, it is distinctive in having the streaking on th ...

, yellow-billed babbler,

brown-cheeked fulvetta The brown-cheeked fulvetta (''Alcippe poioicephala'') is a babbler-like bird belonging to the family Alcippeidae found in the forests of South and Southeast Asia. It was formerly called the quaker babbler in India and common nun babbler in Malaya ...

plain flowerpecker The plain flowerpecker (''Dicaeum minullum'') is a bird in the family Dicaeidae. The species was described and given its binomial name by Robert Swinhoe in 1870. It is found in the central Himalayas, through western Indonesia to Taiwan. Descrip ...

, crimson-backed sunbird, and

little spiderhunter The little spiderhunter (''Arachnothera longirostra'') is a species of long-billed nectar-feeding bird in the family Nectariniidae found in the moist forests of South and Southeast Asia. Unlike typical sunbirds, males and females are very similar ...

. white bellied wood pecker

References

External links

Short film about the Dam by KSEB

External links

{{Dams in Kerala Dams in Ernakulam district Buildings and structures in Ernakulam district Buildings and structures completed in 1985 1985 establishments in Kerala 20th-century architecture in India