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Periyar Basin Hydro Electric Projects

Idukki Hydro Electric Project (IHEP) is the largest hydro electric project in Kerala. Installed capacity of this project is 780 MW. The powerhouse has six generators of 130 MW capacity each . The project was completed with aid from the Government of Canada and the technical consultancy was M/s Surveyor, Nenniger and Chenevert . The project was dedicated to the nation on 12th February 1976 by the then Prime Minister of India, Mrs. Indira Gandhi.There are three Dams associated with this project. They are:  Idukki Arch Dam, Cheruthoni Dam & Kulamavu Dam.
Three Dams Constitute Reservoir of this project, which is the largest Reservoir in Kerala. The Reservoir is spread across Thodupuzha, Peerumedu, and Udumbanchola Taluks in Idukki District. The salient features of this reservoir are listed below.
Water Spread Area 60 Sq. Km.        
Catchment Area   640 Sq. Km.          
Average Rainfall   3000 mm          
Full Reservoir Level (FRL)   2403 Ft (Above MSL)        
Minimum Drawdown level (MDDL)   2280 Ft (Above MSL)        
Effective Storage at FRL   1459.5 MCM        
Energy Equivalent at FRL   2145.47 MU        
Average head at power house   660 m        
This is the first arch dam constructed in India. This is a double curvature parabolic arch dam, constructed across the river Periyar. With a height of 168.91 meters, this is a second highest dam in India. Length of the dam at top is 365.85 meters and width at top is 7.32 meters.
Constructed across the Cheruthoni River, at Cheruthoni in Idukki, this is the largest Straight gravity concrete dam in Kerala. Height is 138.38 meters and length at top is 650.9 meters. There are five radial gates in the dam to release the water from the reservoir. Among the three dams, only Cheruthoni dam is having the radial gates.
Constructed at Kulamavu, in Idukki district, across the river called Kilivallithodu, this is a gravity dam with the top portion in concrete and the bottom in masonry. The height is 100 meters and the length is 385.06 meters.
There have been consistant efforts to increase the inflow to the reservoir, thus making it possible the following diversion projects.
1.      Kuttiyar Diversion                  
2.      Vadakkepuzha Diversion                  
3.      Azhutha Diversion                  
4.      Narakakkanam Diversion                  
5.      Kallar/ Irattayar Diversion                  
This Underground Power Station is a technological achievement in many aspects. The powerhouse cavern with length of 141 meters, 20 metres in width and 34.5 meters in height is the biggest of its kind in the country. The entry to this cavern is through an access tunnel, 599 meters in length. Vertical Pelton turbines are used in the station. There are six generating units each of 130 MW capacity. The 220 KV switchyard is situated outside the powerhouse cavern and it is from here that power generated in the station is transmitted to load centres. There are seven 220KV feeders for this purpose, including the Inter-state Idukki-Udumalpet feeder. The power generated in the powerhouse is taken to the switchyard through 220 KV oil filled cables.After power generation, water from the power station is released to the Thodupuzha River through an underground tunnel, 1220 meters in length. This tail race water is used for power generation in the Malankara Small Hydro Electric Station and also for irrigation purpose with the help of Irrigation dam at Malankara.
Place       Moolamattom      
Village       Arakulam      
Taluk       Thodupuzha      
District       Idukki      
Installed capacity       780 MW      
Firm annual generation capablity 2398 MU          
Prime mover Vertical Pelton Turbine      
Unit Rating Date of Commssioning
U # 1 130 MW 12.02.1976        
U # 2 130 MW 07.06.1976        
U # 3 130 MW 24.12.1976        
U # 4 130 MW 04.11.1985        
U # 5 130 MW 22.03.1986        
U # 6 130 MW 09.09.1986        
Power Evacuation The power generated in the under ground power house is taken to Moolammatom switch yard throug 220 kV Oil filled cables. Power evacuation to load centres is through 6 Nos 220 K.V feeders and 2 Nos 66 KV feeders
Generation in MU for the last Six years
Year 2009-10 2010-11 2011-12 2012-13 2013-14 2014-15
Genearion in Mu 2035.635 2264.51 3041.71 1562.71 2741.87 2492.58
The tail water from 780 MW Idukki Power Station forms the main water source for Malankara SHEP. The Dam toe Power house located in Karikodu village in Thodupuzha Taluk of Idukki District, has installed capacity of 10.5 MW (3 x 3.5 MW). The station utilises the excess water available in the Malankara reservoir after irrigation requirements. The project was dedicated to the nation on 23.10.2005. M/s SILK Ltd, Thrisssur carried out the design, supply erection, testing and commissioning of the Powerhouse equipment in collaboration with M/s Koessler Austria.
The reservoir is formed by the MVIP dam at Malankara, owned by the State Irrigation Department.
Water Spread Area 4.66 Sq. Km.        
Catchment Area   153.5 Sq. Km.          
Full Reservoir Level (FRL)   +42m        
Minimum Drawdown level (MDDL)   +36m        
Gross Storage at FRL   37.3 MCM        
Energy Equivalent at FRL   0.53 MU        
Place       MALANKARA      
Village       KARIKODE      
Taluk       Thodupuzha      
District       Idukki      
Installed capacity       10.5 MW      
Firm annual generation capablity 44 MU          
Prime mover       horizontal shaft Kaplan          
Date of Commissioning of units
Unit Rating Date of Commssioning        
U # 1 3.5 MW 27.08.2006        
U # 2 3.5 MW 06.08.2005        
U # 3 3.5 MW 06.08.2005        
Power evacuation The power generated at the station is transmitted through the 66 kV Malankara - Moolamattom and Malankara -Thodupuzha feeders.
Generation in Mu for the last Five years from Malankara SHEP
Year 2009-10 2010-11 2011-12 2012-13 2013-14 2014-15
Genearion in Mu 32.45 36.90 31.94 26.47 30.39 33.77