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Location & tributary information
Latitude 10deg18’45’ N Longitude 76deg38’10’’ E
Chalakudy has its origin in Annamlai region and is fed by four main tributaries sholayar,parambikulam,thekadi and karapara. Catchment area is 1390sqkm.Annual average rainfall is 3560 mm.It receives rainfall from southwest and northeast monsoon.
The power station is divided into two main regions, one consisting of four 8 MW generators, known as the Old Block and another consisting of a single 16 MW generator known as the Poringalkuthu Left Bank Extension, or PLBE. The maximum generating capacity of the plant at this time is 48 MW, however future additions are planned and would expand the capacity of the plan to 72 MW with the addition of another 24 MW generator in the PLBE building.
The Old Block is broadly divided into three floors, the topmost floor is where the control machinery is situated and is known as the Control Floor. The next floor houses the generators themselves and is known as the Stator Floor. The third and last floor is situated below the Stator Floor and houses the turbines. The main shaft of the machine spans the entire three floors and transfers the mechanical energy from the turbine to the generator, allowing it to convert it to electrical energy.
All four generators in the Old Block are manufactured by The English Electric Co. which was a British industrial manufacturer founded in 1918. These generators are smooth cylindrical core types with 10 poles, running at approximately 600 rpm. In general operational modes, one of the generators remains in stand-by mode while the other three run. However, since the dam was in risk of spilling, all four generators were operating and the plant was at full capacity.
Poringalkuthu Left Bank Extension Scheme having an installed capacity of 16 MW (1 x 16MW) is an extension to the existing Poringalkuthu HEP. It is owned, operated and controlled by Kerala State Electricity Board. Poringalkuthu HEP is located at Chalakudy river in Mukundapuram taluk in Thrissur district. The PLBE scheme is materialized by putting up a fifth pipe line of 1750mm diameter from tunnel exit to the new power house. Both the Poringalkuthu & PLBE power station is being operated as a peak load station during monsoon period and base load station during off monsoon period. The foundation stone was laid by Sri. C.V.Padmarajan, Honorouble Minister for Electricity for Kerala on 1994 Nov 15. The expenditure incurred for the materialisation of the project was about Rs 41 crores.
The PLBE power station commenced operation 20/03/1999. The power house accommodates one number vertical shaft Francis type turbine designed for direct coupling with 3 phase, 50 Hz, 16MW generator, designed and manufactured by BHEL. A penstock of diameter 1.75 m feeds the unit. Spherical valve has been provided before the unit for the safety of the unit. A pressure relief valve has also been provided to limit the pressure rise and speed rise within desired limits. Provision has been kept for removal of runner from bottom without dismantling the unit.
The power house is having Francis vertical turbines with an average head of 173.3 meters, coupled with a 16 MW synchronous generators of 11 kV generation voltage and rated power factor of 0.9 lag. The power generated is stepped up to 110 kV and is connected to the Chalakudy 110 kV grid substation through two feeders. A third feeder is connected to the Sholyar power station at 110 kV.
The Chalakudy river has its origin in the Anamalai ranges and is formed and fed by four main tributaries, viz. Sholalyar, Prambikulam, Thekkadi and Karappara rivers. The Sholayar river draining an area of about 259 sq.km s. (100 sq.miles) rising in the escarpment of the Eastern Ghats of Anamalai, first flows in a Westerly direction for (28 miles) 43 Kms. And takes a turn towards north and falls rapidly, to join Parambikulam river at Orukombankutty at an elevation of about 457 m. (1500ft.)
The Parambilkulam river draining an area of 357 sq.kms. (138 sq.miles) rises in the Western Ghats and flows in a Westerly direction almost parallel to Sholayar and about 8 Kms. (5 miles) north of it. This river joins the Thekkadi river at Kuriarkutty and flows to Orukombankutty.
The Thekkady river draining an area of 150 sq.kms (58 sq.miles) also rises in the Western Ghats at the Northern end and flows Southwest to join Parambikulam river at Kuriarkutty. Portions of the above three rivers flow through Tamil Nadu territory , the drainage area of this portion being 320 sq.kms. (123 sq.miles).

The Karappara river draining an area of 137 sq.kms. (53 sq.miles) rises in the Nelliampathy State Forest in the North, flows West-ward and turns south, then South-East and joins the main river at Orukombankutty about 2 Kms down stream of the confluence of Sholayar and Parambikulam rivers. From this point onwards the river is known as Chalakudy river.
The main falls in the river area at Poringalkuthu and Athirappally. After Kanjirappally, the river takes a torturous course of 35 Km and finally empties into the right arm of Periyar.
The Chalakkudy river is Perennial in flow and after a meandering course of 136 kms. (85 miles) in all, joins the northern arm of the Periyar River and empties into the back waters to the South East of Crangannore bar.