The power house that named this waterfall switched on in March 1940

The waterfall is named after a machine, and the machine is 836 metres up the same bank of the Muthirapuzha. In March 1940 the Travancore Diwan, C. P. Ramaswamy Iyer, started the first generating unit at Pallivasal, and Kerala had hydroelectric power for the first time. It happened during the reign of Sree Chithira Thirunal Balarama Varma, and the township that grew around the station carries his name: Chithirapuram, 1.1 km from these rocks.

Six Pelton wheels

The second unit followed in February 1941 and the third in February 1942 — three Pelton wheels supplied by Escher Wyss of Switzerland, uprated in 1950 from four and a half megawatts each to five. A second phase added three more Pelton sets of seven and a half megawatts from Boving of the United Kingdom, and built the Kundala and Mattupetty dams upstream to store the water that would run them. That took the station to 37.5 MW and something in the order of 284 million units a year.

Pelton wheels are the giveaway, incidentally. A Pelton is the turbine you use when you have a modest quantity of water falling a very long way, which is exactly what the High Range offers and exactly what the flat country downstream does not.

The weir that decides how much river you see

In 1944 a masonry weir was completed on the Muthirapuzha upstream, ten point nine metres high from its deepest foundation, thirty-nine point six metres long, with three spillway gates of 11.60 by 6.70 metres and about 0.223 million cubic metres impounded at full reservoir level. Its purpose is not storage in any real sense. Its purpose is to take the river out of its own bed and send it through a conducting system to the power house on the right bank.

Which is why the waterfall below the station behaves the way it does. Between the weir and the power house the Muthirapuzha is a river with most of itself removed. Below the power house it is a river that has been given back, through six turbines. What comes over the slabs on a dry afternoon in March is, to a large extent, whatever the grid asked for that day — and that is the mechanism behind the one-line review on this waterfall that reads "No water. Not good to visit in summer season".

A cascade, not a station

Pallivasal is one link in a chain. The Muthirapuzha is a tributary of the Periyar and it has been engineered along most of its descent: Kundala and Mattupetty above, Pallivasal here, then Sengulam and Panniyar below, so that the same water turns three sets of machines before it reaches the plains. It is among the oldest cascades of its kind in India, and it is why a district with almost no industry has three power houses within fifteen kilometres of each other.

The fourth power house

There is one more, and it has never generated anything. The Pallivasal Extension Scheme is a 2 × 30 MW project — sixty megawatts, 153.90 million units a year — with a power tunnel of about three and a half kilometres, a pressure shaft of some 1,131 metres and a penstock of 1,285 metres, feeding a new power house at Chithirapuram whose tailwater would run by gravity into the Sengulam reservoir.

KSEB accorded revised administrative sanction on 20 November 2001, for ₹269.87 crore. The execution contract went to the ESSAR–DEC–CPPL consortium at ₹268.01 crore. On 13 September 2018 the board terminated it for poor progress at site. The building in the photograph at the top of this piece is that power house, 1,065 metres from the waterfall.