The Manuherikia Falls Dam is a structure born of the distinct conditions of Central Otago. Water has dominated the affairs of humans in the area - from the earliest days of travel when it impeded progress by its flow or shortage, to the gold rush when it was needed to win the gold and feared for the occasional floods which destroyed walls and races and swept away tents and occupants, and the farming era, when the possession of water rights, sometimes inherited from the miners, was essential for making the strong Central sunshine grow a crop.
The regulation of the Manuherikia was a long-contemplated project. To reduce the threat of flooding and instead put those floodwaters to use when there was no rain would make a massive difference to the downriver farming economy.
The only problem, of course, was the cost. Initially, it was in the boom years of the 1920s when it seemed feasible to build a dam where the river began its course down a rocky gorge.
PUBLIC WORKS STATEMENT
THE MINISTER’S PLANS. EXPENDITURE OF OVER 4 1/2 MILLIONS. (excerpt)
An extensive programme of Central Otago irrigation works is outlined, including the Upper Manuherikia, which involves a dam costing a quarter of a million, though a supply will be available from the old mining race before the dam is completed. -Evening Star, 28/10/1924.
Mr F. W. Furkert (Chief Engineer, Public Works Department) and Mr J. R. Marks (District Engineer) made a flying tour of the works in Otago this week, starting from Dunedin on Tuesday morning, and returning last night. They looked at the Taieri flood protection constructions; they inspected every undertaking of importance between the Taieri and Tarras. Mr Furkert spoke in particular, before leaving this morning, as to the importance of the proposed Manuherikia Falls dam. The site is fixed, and the area that it is to command is surveyed. The location of the dam is three and a-half miles from the point where the road to Oturehua and St. Bathans crosses the river, not far from the Hawkdun Station. The dam is to be the biggest in the South Island, and one of the most capacious in the Southern Hemisphere, and it will enable all the country between St. Bathans and Clyde to be irrigated from the Manuherikia River. -Evening Star, 2/1/1925.
The building of the dam was presumably too expensive in the mid-1920s. But the Great Depression made it feasible by setting up conditions for a cheap labour force.
Cabinet has authorised the Omakau-Lauder irrigation scheme, and the district engineer of the Public Works Department (Mr T. M. Ball) is awaiting details. This scheme means the construction of a dam at Manuherikia Falls, and it will irrigate an area of about 12,000 acres in the vicinity of Lauder and Omakau. It is understood that the navvy work is to be done by married men who were employed until recently on the South Island trunk railway construction. -Evening Star, 28/10/1931.
Manuherikia Irrigation Scheme
A gang of 110 men, who have been transferred from the South Island Main Trunk line, will begin work next week on the construction of a dam at the Manuherikia Falls, near St. Bathans, which will supply the water for the new Manuherikia irrigation scheme. After they have prepared the road which will give access to the site, the men will be concentrated on the building of the wall of the dam. The wall will be the type known as ‘'rock-filled,” an advantage being that a larger proportion of the total cost will be spent on labour than would otherwise be the case. The height of the wall will be 100 feet, but when a greater holding capacity is required the height can be increased to 150 feet without the sacrifice of any of the work already done. The dam will supply water for an area of approximately 14,000 acres in the Omakau, Lauder, and Matakanui districts. At a later stage more men will be transferred from the Main Trunk line and will be placed on race construction work near Omakau. There will be no vacancies for Otago men, as the employees are merely being transferred from one Government undertaking to another. The scheme is classed as a relief work, and payment will be based upon the relief rates of 12s 6d a day for married men and 9s for single men. The men have been given permission to leave their wives and families in the huts which they previously occupied in Marlborough. It is probable that the work will be continued during the winter months. -Otago Daily Times, 3/11/1931.
Mr T. M. Ball, District Engineer, Public Works Department, in the course of an inspecting tour last week, saw and gave further directions in connection with the preliminaries for the construction of the Manuherikia Falls dam which is to collect water to supply the intake at Becks and thus to irrigate the land between Omakau and St. Bathans. The site of the dam is two and a-half miles up-stream from where the Manuherikia River crosses the road leading to St. Bathans. It is to be a rock-fill dam, 100ft high, the idea being to afterwards raise it to 150ft when the demand warrants the heightening. The power house and plant used for making the Poolburn dam are to be shifted to the Manuherikia Falls and give the energy required for the new work. Fifty men are now forming the service road on which the necessary material is to be conveyed to the dam site, and sixty more are to be put on this week. The purpose is to store water in the summer, and thus to have a reserve so as to compensate for the lessened inflow when the stream is low. -Evening Star, 16/11/1931.
Deaths
MONK. — On October 31, 1932, at Manuherikia Dam. Mary Ann, dearly beloved wife of John Frederick Monk ; aged 54 years. Funeral at 2.30 p.m. on Wednesday. 2nd inst., at Omakau Cemetery. Otago Daily Times, 1/11/1932.
A start has been made upon a dam, 153ft in height, across the Manuherikia River, near St. Bathans, which is known as the Falls dam. This dam will form a reservoir that will conserve 40,000 acre-feet of water for irrigation, in the Manuherikia Valley, of land lying between Lauder and Omakau. At the present time about 100 men are engaged in its construction. The dam is of the rock-fill type, with a concrete impervious up-stream face. This type was chosen as one that is simple and economical to increase in height at a later date, and one in which much the greater part of the expenditure is upon labour, so that men put off other public works could obtain employment and not help to swell the ranks of the unemployed. The base of the dam is being made only sufficiently wide at present for a dam 103ft in height, but the other works are of such dimensions as to allow for a dam 153ft high if experience shows that it will be profitable to extend the area irrigated. A diversion tunnel 600ft in length and 17ft in diameter is needed to dewater the foundations, and the driving of this tunnel is now well advanced. The clearing of the dam foundation is completed, and two quarries for rock have been opened up and a start made on the rock-filling of the dam. Electric power generated from Diesel engines is used for the plant required on the works. To coincide with the completion of the dam, a sufficient number of men are engaged upon race construction between Lauder and Omakau, so that it will be possible to irrigate 8,000 acres here immediately the dam is ready to supply water. There are thirty miles of main race to make, and three miles are completed. In addition to ninetyeight married relief workers, fortyfour single men are employed in race cutting under the Unemployment Board’s scheme of camps for single men. -Evening Star, 23/11/1932.
Diesel engine foundations, still visible on the flat below the Dam. Also visible are scraped areas, presumably for accommodation, concrete foundations for power poles and non-native flowers and other plants of the kind planted by people staying in an area for a while.
UNEMPLOYMENT
MARRIED QUARRYMEN WANTED WORK AT MANUHERIKIA DAM.
There are at present vacancies for married quarrymen at Manuherikia Falls dam. These men will be placed on contract, and will be able to earn 10s to 12s per day. There will be continuous work for the right men, but it should he noted that there is no accommodation for a man’s wife or family. Some are required to hold quarrymen’s certificates, but any men with quarry experience and who are used to working compressed air tools will be sent. Applications should be made to the Government Employment Bureau. -Otago Daily Times, 21/1/1933.
GELIGNITE EXPLOSION
ACCIDENT AT MANUHERIKIA
THREE MEN INJURED
While working on the west quarry at the Public Works dam at Manuherikia, near Oturehua, yesterday afternoon, three men, all belonging to Dunedin, were injured by an accidental explosion of gelignite, and all were subsequently admitted to the Maniototo Hospital at Ranfurly. The injured men are: —
Kenneth Cameron, aged forty-five years, of 21 King Edward street, South Dunedin, seriously injured.
John Scoles, aged thirty-four years, of 17 Grosvenor street, Kensington, deep cuts about the head and face.
John Pauley, aged forty-six, of 27 Richardson street, minor injuries.
All three injured men are married. The accident occurred about 1.45 in the afternoon, and it is surmised that on the face of the quarry, where a gang of fourteen men were scattered about, a charge of gelignite had previously been laid, a plug of which had apparently slipped into a crevice in the rock and remained there. When this was touched by Cameron’s pick the explosion occurred, and Cameron received serious injuries to the head, arms, chest, legs, and right eye. Scoles received deep cuts about the head and face, and Pauley suffered minor injuries.
Dr Scrymgeour, of Omakau, was quickly communicated with, and arrived soon afterwards, ordering the despatch of the three men to the hospital at Ranfurly.
Inquiry from the Maniototo Hospital this morning showed that Cameron’s condition was still very serious. Pauley and Scoles were both suffering from shock, but their condition to-day was satisfactory.
It is stated that this is the first accident that has occurred in the quarry at Manuherikia. -Evening Star, 25/8/1933.
Manuherikia Falls Dam
The construction of the Manuherikia Falls dam, which will regulate the supply of water for the Omakau irrigation scheme, has been advanced another stage. The river has been turned into the diversion tunnel, and work can now be put in hand on the section over which the river previously flowed. The dam, which is of the rock-filled type, will be 100 ft high, and the cost will be in the vicinity of £100,000. The tunnel through which the river is now flowing is 10 chains long and 17ft in diameter. It is lined with concrete. Owing to the nature of the gorge the ordinary type of spillway cannot be constructed, but the tunnel through which the river is now being diverted will ultimately be used for this purpose, and the intake will be made in the form of a funnel leading into it. This is the type of spillway which is being constructed for the Hoover dam, on the Colorado River, the largest dam in the world. It is interesting to note that the new Manuherikia Falls dam, which is near St. Bathans, is only 28 miles distant from the Waitaki hydro-electric dam. The work will probably occupy another 12 months. -Otago Daily Times, 14/7/1933.
The construction of the Manuherikia Falls dam, which is to provide water for the Omakau irrigation scheme, is proceeding apace under the direction of the Public Works Department’s officers. The bulk of the stone filling has been placed, and the men are now engaged on making the concrete slabs for the front of the dam. The main race for the Omakau scheme is nearing completion, and the syphons that are to carry the water across the valleys are at present in preparation. One of those syphons will be a mile long. The pipes for this work are being manufactured in Dunedin by the Hume Pipe Company and McSkimming and Son Limited. -Evening Star, 3/5/1934.
IRRIGATION
UPPER MANUHERIKIA
HUGE DAM AT FALLS
WATER FOR OMAKAU BASIN (excerpt)
A £113,000 DAM. The main feature of the work, therefore, is the huge dam structure at the falls, behind which 8000 acre-feet of water will be stored. It should be explained here that an acre-foot of water is the amount of water that would be required to cover an acre of ground to a depth of one foot.
The dam, which is now rapidly approaching completion, will be 110 feet in height, and of the rock-filled type. It will have a maximum base width of 350 feet, and the length of the crest will be 520 feet, and its width 14 feet. The main bulk of the dam is composed of rock-filling, while the whole of the upstream side of the structure is faced with reinforced concrete slabs two feet thick, made up of 44-foot units, placed separately to allow for future settlement. Each unit will be joined to the next by means of waterproof copper strips. The lower edges of the bottom seaps rest firmly on a massive concrete cut-off wall. Between the two bottom rows of slabs there are 160,000 cubic yards of loose rock filling. Another feature of the structure is a huge reinforced concrete hinged block, designed to give flexibility to the face in case of a settlement of the rock filling. All the joints between the slabs are being filled with a special bitumen compound.
The dam will have a freeboard of 13 feet above the lip of its spillway, which is up-stream, with a circular lip 100 feet in diameter, diminishing funnel-wise to a shaft of 17 feet in diameter, connecting with a diversion tunnel of the same diameter, which discharges into the riverbed on the down-stream side of the dam. The diversion tunnel is 10 chains long and fitted with control valves by means of which the water may be released as required. After the water has been released through this tunnel it will travel 10 miles downstream, where it will be picked up at an intake near Blackstone Hill. the main race. It is here that the main race commences its 31-mile winding course through the country that will be served by the scheme. -Otago Daily Times, 28/7/1934.
IRRIGATION SCHEME
COMPLETION IN OTAGO
(By Telegraph.)
(Special to the "Evening Post.")
DUNEDIN, This Day. The Omakau irrigation scheme is approaching completion. It is expected that the Manuherikia Falls dam will be closed for the storage of water in a fortnight, and that the water will be turned into the main race about October 9. Farmers and orchardists in that region who need irrigation are therefore likely to have their wants supplied very shortly.
The whole scheme governs 15,000 acres. One section cannot be finished just yet, the Lauder section of 3000 acres lying above most of the country thereabouts. On that section, however, water rights are already acquired. The Falls dam is the biggest work of its kind in Otago. -Evening Post, 20/9/1935.
I imagine that there was a miniature gold rush along the newly and temporarily exposed bed of the Manuherikia where it was exposed by the filling of the Falls Dam. The Dam itself was only part of a wider scheme which takes water from the Manuherikia and sends it to farms in the area and which, since 2003, generates electricity.
Plans to build the dam higher for more storage have been contemplated since the 1950s.
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