The Mullaperiyar Dam and Tunnel
" of the most extraordinary feats of engineering ever performed by man"1




Other sources

  1. Photographs from the 'Periyar Album', 1889-1896, property of Stuart Sampson
  2. Conversations with Stuart Sampson (great-grandson of Col. John Pennycuick) and Tom Gibb (grandson of James A.C. Pennycuick)
  3. Waterlines - the Penguin book of River Writings, ed. Amita Baviskar, New Delhi, 2003, including An Ode to an Engineer by Anand Pandian
  4. The Royal Geographical Society monthly record, December 1895
  5. 'The Pennycuicks', notes written and compiled by James A.C. Pennycuick and Janet Buchanan (.pdf file)
  6. Conversations with Santhana Beer-Oli, film-maker


Mullperiyar Lake SW
Map 1: Southern India, showing the Cardamom Hills, the Periyar and Vaigai rivers and the Mullaperiyar Reservoir. The watershed is roughly concurrent with the border between the states of Kerala and Tamil Nadu.

Microsoft / HERE Maps

Mullperiyar Reservoir
Map 2: The Mullaperiyar Reservoir: the Periyar flows in at the bottom of the map and is dammed; water is led off from a northerly arm of the lake, through a tunnel under watershed, and channeled towards the Suruli river. The Periyar flows out from the dam to the left of the map.

Microsoft / HERE Maps

Various alternative plans

Pennycuick was involved in the discussions about the dam for several years before being given the task in 1882. He had examined Ryves's proposals in 1870,1 but departed that year for England on a medical certificate, and Mr. R. Smith took over.3 Smith's proposal was for an earthwork dam 175 feet high with a 7,000 foot tunnel, but this was rejected: the flow of the river was such that any dam would at some point be submerged during construction - fatal for an earthwork dam.

Smith and Pennycuick also considered the possibility of a masonry dam: although more expensive and at the time comparatively rare, they can be submerged during construction without damage.

Different possible sites were looked at: the one finally adopted was seven miles downstream from Ryves's proposed site: the height difference to the watershed was less, so the dam could be considerably lower, and flatter ground meant the reservoir would be larger. Pennycuick makes no mention of Mr. Smith in his account, but says that his own first proposal, for a 200 foot earth dam, was ("rightly") rejected.

Mullaperiyar site


Map 3: Construction Site for the Periyar dam, showing the temporary cross-dams

Mullperiyar Dam
Map 4: The Mullaperiyar Dam (satellite photo), showing the dam, below it the left-bank 'extension', and above it the right-bank 'escape' (weir)

Microsoft / HERE Maps

Mullperiyar Lake W
The Mullaperiyar Lake and Dam from the west

Google Earth

Silver spade


Silver spade made by P. Orr and Sons, Madras, commemorating the start of construction work on the Periyar dam in 1888

Family heirloom

Mullperiyar tunnel


Map 5: The Mullaperiyar tunnel (section)

Diagram from Institution of Civil Engineers paper by Parker Roscoe Allen

Photographs by Sir John Pennycuick

Col. John Pennycuick's son Sir John Pennycuick visited the Mullaperiyar site, probably in the 1960s, and took several photographs (he was keen 'postcard' photographer), five of which are shown below (see also title photo). An article from an Indian newspaper describing the visit is shown on the page for Sir John.

Mullperiyar site
Another view of the Periyar Dam showing the Commemoration Stone
Mullperiyar site
View of the Periyar Dam showing its width
Mullperiyar site
Sluice gates of the Periyar Dam
Mullperiyar site
Another view of the Periyar Dam
Mullperiyar site
Cemetery near the Periyar Dam showing the graves of British officers and soldiers who died during the time of its construction


A certain mythology has grown up around Col. John Pennycuick and the Mullaperiyar Dam, not all of it positive. In addition to the three very precise accounts of the dam's construction1,2,3 (with which this website mainly concerns itself), there are many articles in the internet dealing with the man and his work, some with stories which are more or less apocryphal.6,7,8,iii For example, according to various accounts, the failure of the cross-dams in March 1889 (see above) caused the British-Indian government to stop the funds for the project. One version has it that Pennycuick was fined by the government. In both of these, Pennycuick had to use his own money (by selling property or jewellery) for the project to continue.5 While not impossible, this is regarded by family members I have consulted as unlikely.ii Certainly Pennycuick makes no mention of any this in his account.2

Hydroelectric power

In the 1890s hydroelectric power was in its infancy, but it was clear at the planning stage that the steep fall of water on the Madurai side of the tunnel (1,200 feet over a mile) was ideally suited for  driving power turbines, and the large volume of water in the lake would ensure a constant flow throughout the year.2 Pennycuick calculated that the cost-benefit balance of the dam, already favourable, would be improved significantly when the possibilities of hydroelectric power were harnessed.

The power station at Lower Camp, on the eastern side of the watershed, was built in the 1950s and 1960s. The capacity is now around 180 megawatts.5

Mullperiyar Dam
The Mullaperiyar Dam

Photograph: Sir John Pennycuick (son of the engineer)

One of the boldest irrigation projects in India,1 the damming and dividing of the Periyar river at Thekkady, causing water to flow to the other side of a watershed, was Col. John Pennycuick's enduring work, for which he is still revered in the Tamil Nadu region.

Research on the building of the dam is greatly helped by the availability of the original project descriptions by A.T. MacKenzie (executive engineer) and by Col. Pennycuick himself (Chief Engineer). In addition, Stuart Sampson has generously provided photos taken during the project (the 'Periyar Album').

The watershed

The Cardamom Hills in southern India form the watershed between the Arabian Sea and the Bay of Bengal, along which runs the border between two states of Kerala and Tamil Nadu (formerly Travancore and Madras) (see Map 1). Two rivers have their sources here: the Vaigai and its tributary the Suruli flow eastwards to the Madurai region, which, being in the rain shadow of the mountains, suffers acute water shortages in dry years; the Periyar flows westwards through dense jungle, where severe flooding is frequent, down to Cochi on the coast. What if the Periyar could be diverted eastwards across the watershed, reducing at a stroke the problems of water shortage and over-abundance...?

From its source just west of the watershed, the Periyar flows northwards for several miles, before it and the watershed turn and run westwards for about 10 miles; the river then turns north-westwards towards Idukki. In some places the river bed is only 200 feet below the watershed. If the Periyar could be dammed in this section, a large lake would form, raising the water level and filling various side valleys. From the valley nearest to the watershed, the water could be led off, through or under the mountains, and channelled down to join the Suruli and Vaigai rivers, and so to the Madurai plains. This simple and intriguing idea had existed for a long time, but was first investigated in the early 19th century, and came to fruition 100 years later with the Mullaperiyar Dam and Tunnel.

A brief feasibility study was carried out by Capt. James Caldwell in 1808, but as it involved a cutting 100 feet deep through the watershed, he dismissed it as impracticable. Following the change of administration in the middle of that century, the idea was revisited in 1862 by Major J.G. Ryves of the Madras Engineering Corps. He made detailed investigations of the region over five years, submitting a proposal in 1867 for an earthwork gravity dam 162 feet high, and cutting. (A gravity dam, which relies on the sheer weight of the dam wall to hold the water in, is built of stone, concrete or earth, the latter being flatter in section. Modern dams, such as that at Idukki, further downstream on the Periyar, have much thinner concrete walls, curved vertically and horizontally to withstand the water pressure.) Major Ryves's plans were delayed, but also given renewed urgency, by the terrible famines of 1876-77, and in 1882 Maj. John Pennycuick of the Madras Engineers was given the task of preparing a detailed proposal.1 (See side note for details of other proposals.)

Silver spade


"In commemoration of the Turning of the First Sod in the Periyar Distribution Works on the Plains of Madura, Col. John Pennycuick RE, 1888"

Family heirloom

The plan

Pennycuick's extraordinarily detailed proposal, submitted in 1882 and covering over 16 pages of MacKenzie's book,1 was for a concrete gravity dam 155 feet high (plus 5 foot parapet). (This is 150 feet above the surveyed 'datum line' - the actual depth of water at the dam wall is 18 feet more than that.) A large lake, about eight miles long, would be formed by the dam, and from the end of the northernmost inlet, a cutting and tunnel would lead through the watershed (see Map 2). After exiting the tunnel, the water would flow down a steep gradient to Lower Camp (where a hydroelectric power station could be situated - see side note below left), and from there along channels to join the Suruli river.

The plans were approved in 1884, and the go-ahead for construction given in late 1887. Preliminary work began that year, and construction at the dam site itself began in 1888, commemorated by a beautiful silver spade presented to Col. Pennycuick (see photos above and left).


The dam site was in the middle of uninhabited jungle, presenting serious challenges from the outset. From April to June the dangers of jungle fever were too great to allow any kind of work, leaving a 'construction season' of nine months (July-March). This was further restricted by the SW and NE monsoons (July-August and November-December), making work on the river bed impossible, and other work slow. The nearest road was 7 miles away, the nearest farm 20 miles and the nearest railway 80 miles.

The first season (1887/88) was spent building a road to the construction site, and accommodation for the workers and engineers. In addition, a canal was built to transport materials to the dam, following the line of a small river (the Mulya Panja) which flows from Thekkadi into the Periyar upstream of the dam.3 Pennycuick travelled to England in early 1888 to order machinery for stone crushing and tunnel boring. Work on the dam and the tunnel started in late 1888.

Periyar foundations


Foundation enclosure from N, ca. 1890

The stone piers of the coffer dam can be seen on the L and R banks

In order to build the dam, water had to be diverted from above and below the site. Pennycuick's original proposal was for a small temporary stone dam upstream of the main foundations, with tunnels through the rock of both banks to channel the water past the main dam site. Another temporary dam downstream would prevent the water flowing back into the foundations. Tunnels through the rock were however rejected on grounds of cost (by the "professional advisers of the Government" as Pennycuick puts it - some heavy Scottish irony?) and had to be replaced by a bypass channel on the R bank. (This 'interference' was the cause of most of the difficulties in constructing the foundations, and many of the interruptions afterwards.)

Building the temporary stone dams proved much more difficult than envisaged, as the river bed contained a deep, wide, long chasm, not seen by the surveyors. The first such temporary dam, started in the latter part of 1888, was washed away by unseasonable floods in March 1889; the by-wash channel built for it, seen in the plan of the Construction Site (Map 3), was then abandoned.

Rebuilding the temporary stone dam would have been impossible before the end of the season, so Pennycuick decided to replace it with a 'coffer dam' consisting of wooden shutters placed between masonry piers, across the stream and along the R bank in a ¬ shape, linked to two cross-dams and a L-bank by-wash in a square U shape. The stone piers were completed by the end of March, and survived the summer monsoons.

In November 1889 the spaces between the piers were closed with wooden shutters and sandbags. The inevitable leakage from this structure had to be diverted from the main foundations by the two cross-dams. These were made of wooden trestles, sunk in the river and then filled with earth. It was quite a job to fill these completely so they were watertight, and even so, they had to be watched constantly for sudden breaches, and then repaired. (This was the context of Pennycuick's quote shown below about arrack, a locally distilled spirit.3) They were completed by mid-December 1889.

"Had it not been for the medicinal virtues of arrack, it is difficult to see how the Periyar Dam would ever have been built."

A few days later disaster struck again: the top dam and part of the bottom one were washed away by heavy unseasonal floods, which also took away two of the masonry piers. This time Pennycuick and his workers were able to rebuild the cross-dams without serious loss of time, and in late January 1890 water could be pumped out of the completed structure, albeit with considerable leakage. The whole foundation area was now encased in a wooden wall, with an additional outer wall upstream of it, similar to a letter g on its side (see above photo of the foundation enclosure).

Periyar foundations


The main dam wall from S, March 1892

There was now just time to construct the outer walls of the main foundations before the end of the building season. These masonry walls, some 25 feet thick, were begun at each bank, working towards the centre. Closing the gap in the middle was accomplished by dropping bags of cement and concrete into still water, the main flow having been diverted. This work survived a small flood in February with only minor damage, and by the end of April the foundation walls stood at about 20 feet high. Pennycuick later described the period between December 1889 and April 1890 as "the most anxious, difficult and exhausting of any that had come within his experience".3,iii

Periyar dam wall 1894


The main dam wall from N, February 1894

In the middle of the wall is an access shaft for the tunnel (see text)

Work on the foundations and then the dam walls themselves recommenced in June 1890. After a time, the R-bank by-wash was superseded by a system of vents to channel the river water through the slowly rising dam walls. The vents were replaced in 1892 by a small tunnel, with an ingenious sluice system for controlling the rate of flow. This tunnel was used successfully until March 1895, when (helped for once by unusually dry weather) it was blocked off, allowing the reservoir to fill. A temporary 'escape' (or weir) was built on the L bank, lower than the main R-bank escape, allowing the dam to be raised to its full height.

The main 'escape' is on the R bank, with a height of 144 feet, i.e. 11 feet below the top of the dam. On the L bank there was a small 'saddle' between the dam and the side of the valley. Originally it had been planned to have an escape here as well, but the rock on the south side was unsound, so the saddle was closed by a small masonry dam similar to the main one (the 'left-bank extension') joined to a small earthwork dam.

The dam was essentially completed in the autumn of 1895, and water was sent though the tunnel to Madurai for the first time. See below for details and photo of the opening ceremony.

Periyar dam wall 1895


The main wall of the dam from below (SW), October 1895

A number of ingenious devices reduced the labour and power required on site for building work. Concrete was made using stone-crushing machines driven by belts from a water turbine. The mortar was made of 'Kunkur' limestone (transported up from the Madurai valley using a wire ropeway three miles long, also driven by the turbine) and locally sourced 'surki' (burnt clay or powdered brick). Stone from the tunnel was sent down to the stone breakers by a tramway. Food for the workers (several thousand, according to Pennycuick!) was brought from Thekkady to the dam site by water where possible.

Periyar watershed cutting


The cutting between the lake and the watershed tunnel, from N, August 1893

The cutting between the reservoir and the tunnel was along a side valley to the north, the Mulya Panja, where the supply canal also ran. The 'sill' of the cutting, i.e. the point at which it started to slope downhill towards the tunnel, was 113 feet above the river bed, 31 feet lower than the weir, providing a considerable head of water to ensure a consistent flow. On the Madurai side of the watershed, another cutting leads to a natural ravine and so to the Suruli river.1 This is canalised for much of its length, and 86 miles downstream, a channel 38 miles long completes the irrigation distribution system. In India small village reservoirs are linked together for collecting water in the monsoon months, for use in the dry part of the year. The Periyar project tapped into this network of reservoirs on the Madurai side of the watershed, thus increasing the irrigation potential of the scheme.ii

The tunnel

Pennycuick carried out the surveying for the tunnel himself using a tacheometer, to a high degree of precision: the tunnel faces bored from each end met to within two inches, and the length was accurate to 24 feet (over 5,704 feet). The principal engineer on the tunnel construction was Parker Roscoe Allen, whose paper is printed after Pennycuick's in the Institute of Civil Engineers report.2,4 Work was started in 1888, the same year as the dam, from the exit and from a shaft 130 feet from the entrance (see Map 5 - shaft 1 is slightly L of centre). Below this shaft was a complex sluice gate system, which together with gates at the entrance to the tunnel, would allow a constant flow of water (to a future power station) even when the gates themselves were under repair. A second shaft (slightly R of centre in the diagram) was sunk in about 1892.

Periyar tunnel shaft 1


The entrance to shaft no. 1 of the tunnel, March 1892

At the back of the picture are the pulleys for raising and lowering men and materials

The tunnel was blasted out using explosives packed into holes bored with pneumatic drills. The compressors for the drills were powered by water turbines connected with driving belts, or in the case of the second shaft which was not near water, by wood-fired steam boilers. All the equipment had to be transportable by cart on country roads. Using four drills simultaneously, a pattern of some 40 holes was bored in the rock at specific points and angles, which were then filled with explosive and blasted, four at a time. After the debris was cleared the next set of holes was drilled. Work progressed at about 4-5 feet per day. The debris was taken away in small railway trucks hauled by winches, bullocks or manpower.

Periyar opening ceremony


The opening ceremony, 10th October 1895

At the centre cutting the ribbon: Grace Pennycuick

To her left (in black): Lord Wenlock

Left of photo (in white): Col. John Pennycuick

(further details on request)


In October 1895 there was an opening ceremony attended by Lord Wenlock, Governor of the Madras Province.2 The ribbon to open the sluices on the tunnel was cut by Grace Pennycuick, seen in the middle of the photo here with a determined look on her face.

The few remaining items (parapet, R-bank tower etc.) were added afterwards, and the whole project was completed in early 1896. Later that year Pennycuick left India for retirement in England.

The human cost of the whole project was sadly considerable. Hundreds of workers died during the construction: many were washed away in floods while countless others perished from malaria and cholera.5

Pennycuick's hut


Pennycuick's hut at the construction site


Col. John Pennycuick is still held in high esteem in the region, on both sides of the border. Statues of him have been erected, and visitors mentioning their family connection are garlanded with flowers. According to Tom Gibb, a journalist and film maker related to the Colonel, this veneration is not only due to his engineering accomplishment, but also to the central importance of water in Indian society and religion, and of God as the giver of water: humans who provide water receive something approaching deification.ii

The Mullaperiyar (or Thekkady) Reservoir is now a national park and tiger reserve.10

The politics

In recent years the Mullaperiyar Dam has unfortunately become the centre of a dispute between two federal states. While it is not the purpose of this website to discuss Indian regional politics, the basis of the dispute can be outlined briefly.5

As is often the case, the watershed through which the Periyar has been diverted forms the border between two states: originally Travancore and Madras, now Kerala and Tamil Nadu (see Map 1). The reservoir and dam are in Kerala; the water for irrigation and hydroelectric power flows into Tamil Nadu, who also operate and maintain the dam and the Lower Camp power station.

In 1886 an agreement was negotiated between the government of Madras (under British control) and the Maharaja of Travancore: the British would lease the 8,100 acres of land for the reservoir and dam for 999 years at 5 Rupees per acre per year. This agreement was renegotiated between Kerala and Tamil Nadu in 1970. The 'rent' was raised to 30 Rupees, and the charge for electricity was set at 12 Rupees per kWh. The validity of this agreement has since been called into question, as has the power of the government of India to intervene in disputes between states.

The dispute centres on the level of water in the dam. At various times it has been 152 feet, 142 feet and 136 feet, the last of which seems to be the current level. A higher water level means more hydroelectric power and more water for irrigation for the state of Tamil Nadu; the state of Kerala contends that this makes the dam unsafe. General safety concerns have also been raised about the age of the masonry and whether the dam is resistant to earthquakes. A survey even looked into the question of building a new dam.

In 2012 a committee appointed by the Supreme Court of India reported that the dam was structurally, hydrologically and seismically safe.5 But the argument has not died down, and indeed flared up in August 2018 when heavy rains necessitated releasing water from the dam, causing flooding downstream.

Mullperiyar Reservoir


The Mullaperiyar Reservoir

Photo: Rameshng, Malayalam Wikipedia (CC)