Maori who lived in the general area in precontact times named the stream on which the Lower Karori Dam sits. The name Kaiwharahara refers to eating (kai) the black berries of a bush (wharawhara, or astelia banksii) which grew in its valley up from the harbour. Maori are therefore assumed to have used the stream for fishing, gathering, recreation, and as a water source and access way, but the dam site is remote and no signs of habitation there are known.
After European settlement the stream banks were used for farming. From 1869 gold deposits found along the stream led to prospecting, with mining starting in July that year. At least five companies tried their hand, driving mine shafts into the hill east of the stream. The Baker's Hill Co claim was just upstream of today's dam site, and the Golden Crown Co just downstream.
The Lower Karori Dam was completed in January 1878 (not 1874 as has been popularly believed) but was the culmination of a number of attempts to bring water to Wellington over the previous decade. It would be the earliest water works dam to be built by a municipality. Water works dams built by other municipalities appear in the early twentieth century, for example Auckland City Council built a series of timber dams in 1901 and Petone Borough Council built the Korokoko dam in 1903. Earlier examples of water works dams, such as those at Ross Creek, Dunedin (Register No 4922) from 1867, or in use in mining, were privately built.
Since being designated the capital in 1865, Wellington had grown apace. Significant development of the infrastructure was planned and the population was expected to increase rapidly, with immigration schemes already bringing them in. The population would grow from approximately 5,000 in 1865 to 18,000 by 1874.
In 1867 the Wellington Town Board started planning a water supply scheme for public use. At this time the public were relying on 'minor streams, wells and water collected from roofs' for their water supply. The Town Board had already appointed a Board of Works to oversee any municipal works authorised by the city in 1864, and later that same year the first Town Engineer, [Robert] Mixer Skeet (1832-1894) was appointed. Skeet considered two streams should be tapped for a water supply, the Te Aro (or Waimapihi) Stream in Polhill's Gully (now Aro Valley), for residents in southern Wellington, with the Kaiwharawhara Stream supplying the Thorndon Ward. This latter would be tapped near Baker's Hill (an early name for the area where Raroa Road now crosses above Karori Tunnel). No constructional plans were drawn up because the estimated cost of the work was deemed too high for the city to afford, and factional politics prevented any agreement. Another confusion that dogged these plans was that the Kaiwharawhara Stream was not within the Town Board's boundary. Commenting on these proposals, another engineer George Aicken (a Town Commissioner) suggested a 20ftdeep reservoir of four acres should be built to provide storage for 1214,000 people, a population the town was expecting.
Skeet's successor as Town Engineer was Nicholas Marchant (18361907), who took over in October 1867. Marchant, who would best known for his work on Karori water works, retiring as City Engineer just two months after the dam was eventually finished, picked up the current proposals for a water supply and dam. Realising the financial difficulties attendant on the city funding this scheme, he invited private interests to suggest a publicprivate partnership. Such as had been successful in Dunedin where a private waterworks company had built two water supply dams (on Ross Creek, Register No 4922) for the town, and levied rates to pay for the work. In Wellington an engineer with considerable experience in railways construction in the United Kingdom, Robert Mudge Marchant (no relation) submitted a proposal similar to Dunedin's. He proposed bringing water from the Kaiwharawhara Stream down its right bank until adjacent to Northland Hill, which would be tunnelled to bring the supply through to Tinakori Road and beyond. In a stormy meeting in August 1868, however, ratepayers soundly rejected this proposal.
At this point the Town Board was offered surplus water from a small Provincial Government scheme that had laid pipes from a spring on Tinakori Road, along Hill Street (involving a tunnel) to a tank beside the old General Assembly (site today of the General Assembly Library building). This was used for firefighting, as well as supplying Her Majesty's warships from Browns Wharf. The Town Board declined to buy from this supply, believing that the source would be inadequate for Wellington's growing population and the Government Tank leaky. This spurred the Town Board to push ahead its efforts to develop their own supply.
In 1869 another private venture got under way, returning to tap the Te Aro Stream and reticulate its water. This was by John and William Beck, contractors who had been involved in the Government Hill Street scheme two years earlier. Following the precedent set by the Wellington Gas Company which had ordered pipes for manufactured or 'town' gas supplies, the Becks started by imported their water piping. They had not, however, sorted out their permissions and the Town Board declined consent, in order to protect commercial users of the stream (brewers and bottlers mainly). It is possible that the Becks had started their weir or intake on the stream, from which to divert part of the flow.
The Town Engineer Nicholas Marchant believed the Kaiwharawhara Stream to be the best for a water supply, and spent the next few months measuring its flow. The stream was chosen for its clean water (other streams that originally supplied potable water were being increasingly compromised when also used as sewers). The site was selected because of its elevation (allowing the water to flow by gravity). The Town Board had been promoted to a Borough Council under the Municipal Corporations Act 1867 (though the promotion had been delayed by ratepayer unease over the cost of some of these water works schemes). He took the best aspects of preceding proposals to formally suggest in March 1871 a dam on the stream at Baker's Hill, a tunnel from that point under Baker's Hill to the head of Aro Valley, and at the other end of the tunnel a distributing basin. The pipes which the council had purchased from the Becks, would be used to reticulate throughout the city, starting down Aro Valley.
The site chosen for the dam was favoured because it 'little exceeds two chains in width [44 yards, 40m] at the top and depth of 60ft [18.2m]'. These dimensions were important because it meant that a relatively narrow dam could impound (or store) a useful volume of water. This scheme was costed at £17,358. A Wellington Waterworks Bill was drafted in June 1871 to authorise a loan (of £25,000) to pay for it. This bill also listed the owners whose land would have to be taken before starting the work (and a lengthy period of haggling began over valuations). The Bill gave the mining companies there, who were prospecting for gold, a twoyear breathing period.
The only other issue was arranging jurisdiction over the stream with the Provincial Government. This was handled through a Municipal Corporations Waterworks Bill, which was passed in 1872 and in which the Crown vested the water rights with the corporation.
A waterworks committee had been formed by Wellington City Council in December 1871, and this committee selected all contractors, and oversaw ordering of materials and the progress of work. Another civil engineer, John Blackett (18181893), was contracted to consult in 1872, and a works overseer appointed the following year. The first work contract was the tunnel through Baker's Hill. Ebenezer Short won the tender, started in February 1872 and had it blasted through in eight months. The next work was the distributing basin at the head of Aro Valley (on the corner of today's Raroa Road and Mt Pleasant Road). The Becks were interested in this job (having already considered such a reservoir in the valley) but another contractor, Saunders & O'Malley won it. Their tender of £3,749 was cheapest and they started work early in 1873. The contract for laying 22km of pipelines was also let, in April 1873, to Collie & Co.
The distributing basin was itself a huge and slow job. It was a boatshaped concrete basin, with the ‘bow' facing into the hill through which the tunnel was cut. Built in a small valley nestled up the side of a bigger valley (above Holloway Road), it required very deep foundations (90ft or 27m) for its ‘stern'. A wet winter and a slip of earth into the excavation slowed the project. These works and rising prices of labour and iron consumed more money than intended. By early in 1874 much of the loan raised for the water works had been spent. These financial constraints had ‘rendered it necessary to abandon the large reservoir [on Kaiwharawhara Stream] for the present' (the NZ Mail reported on 17 January 1874) and instead to double the capacity of the distributing basin (to 1 million gallons). Enlarging the basin had been aided by the large slip on the site during earlier work. A water supply would still be achieved without the dam, and to do so a small weir was placed across the Kaiwharawhara Stream to divert a flow into the tunnel. This filled the distributing reservoir and after the reticulated pipes were checked for pressure, the houses of Wellington (that had signed up for connections) started receiving piped water from early May 1874. The Wellington Independent reported that when water was first sent from the distributing basin down the pipes that ‘the full force from the reservoir was flushed through the mains to their extreme range as far as the lower end of Tinakori Road, and the pipes with one exception proved equal to the pressure'. ‘The want of an abundance of water' was a thing of the past, Nicholas Marchant said. The distributing basin filled the role of the dam reservoir for four years. When the dam was built, the basin carried on in the role of a service reservoir.
A second Wellington Waterworks Act, passed in August 1874, authorised a second loan of £25,000. It was stated expressly to be to ‘extend the pipes and construct a reservoir on the main stream'. Marchant restarted work on his plans in September 1874. The following year in May he was authorised to proceed and called for tenders from contractors. J Saunders (presumed to be the same as built the basin) was successful with a quote for £17,195. Saunders was contracted for the work in October 1876 and got under way the following month. He was asked not only to maintain the flow of water coming in through the tunnel from the weir, but to increase it, such was the rising demand from the city. He built temporary works to this end, which probably involved raising the height of the weir or in some other way increasing the offtake from the stream.
Little detail has survived of how Saunders built the dam. It certainly overlaid the original weir and tunnel entrance, and allowed for the prescribed overflow to continue down the stream (via another exit from the tunnel). There is some evidence underneath the dam that the original culvert from the weir to the tunnel entrance was by this stage encased in an arch of bricks, which was then buried as the dam was built up. This brick tunnelling extends from hard rock out to the base of the valve tower, suggesting the original weir may have been at or near the site of this tower.
The dam was to be a puddled clay core dam. The technique of clay puddling in dam building was first used in Britain in the 1760s, in widespread practice by the 1820s, but still used well into the 20th century. To prepare for the clay core of the dam, a trench was built across the valley on the line of the dam. This went down to at least solid rock, and may have gone further. Into this trench was thrown a clay and sand mixture, the clay to be ‘of good and approved quality, well worked with water and passed through the pug mill to free it of stones and rubbish. The use of pug mills to process the clay was relatively new when Marchant used it. Great care to be taken after it [the puddle, was] placed to preserve it from the effects of sun, air, wind, cracks and other flaws.' Working the clay was called ‘puddling' and usually involved barefooted labourers working it with water and their feet. This puddled clay core would provide the waterproof element in the dam wall. As it built up, it was sandwiched between embankments of stony earth in front and behind. Fine material was added immediately adjacent to the clay core, with intermediate material and finally coarse stony material as the outer layer. Each of these layers was progressively sloped closer to the horizontal, leaving angles approximately 1in2 or 3 at the exterior. The upstream shoulder was then covered with a concrete lining about sixinches thick, as wave protection.
Other examples of puddled clay core dams in New Zealand include the Ross Creek No 1 (1867, water supply, Register No 4922), Hochsetter (1877, mining), Druggans (19001902, mining). Bob Offer, a qualified engineer and an expert on dams in New Zealand has noted that the Lower Karori Dam has some features that distinguish it from other puddled clay core examples, in particular the Ross Creek dam that preceded it. These features include:
It is the tallest use of a puddled clay core in New Zealand.
The use of three zones of material on the upstream shoulder, extending from fine material next to the core and moving outwards via intermediate and then to coarse.
The use of a pug mill for processing some of the clay core material.
The use of concrete on the upstream slope, in a thin facing, as wave protection.
The diversion of the line of the off take to ensure that it passed through the right abutment rock and not the dam (contrary to the principal drawing'.
Offer went on to comment that ‘given the innovations used in its construction the dam deserves to be described as a landmark in New Zealand's dam building history'.
Modifications were made to the dam as it was built, so the plans are not exactly as it is now. The cross sections pay virtually no heed to the undulating country on which the dam was set. The bridge to the valve tower was launched from the nearest point, the lakeside rather than the dam crest. The plans show the dam built to a height of 71ft (21.9m), presumably taken from the bed of the stream at the weir. In later investigations, however, Nicholas Marchant said he lowered the top (without specifying by how much), and brought the front or upstream wall 29ft (8.8m) closer to the clay core, to suit the ground. This had the effect of reducing the volume of material needed by the dam and was probably occasioned by the contractor having to make extra excavations for the puddle trench. After digging a bigger trench Saunders placed an extra 1700 cubic yards of puddled clay in it, and an extra 8,000 cubic yards of earth in the dam filling either side of it. In the end his extra expenses brought the dam's total cost to £19,500, and the whole system to £80,000 (and equivalent of $10 million today).
Dam construction took from November 1876 until January 1878. On 24 January 1878 Nicholas Marchant declared it complete and ordered the filling to begin the following morning. It served water to Wellington for the next 124 years.
As part of the dam a valve tower was built to allow access to the water inlet valves (it was and remains connected to the eastern shore by a bridge). Though it was finished with an octagonal structure and capped with an ornate neogothicstyle roof, with which to keep the weather out, the valve tower was an integral part of the dam through which the caretaker could control the outflow of water. A photograph dating from the building of the dam shows how integrated the valve tower is into the dam structure and suggests the structure was completed before the dam was filled in January 1878.
The original design of the dam included two overflow channels, or byewashes, which were completed soon after the dam was filled. ‘Byewash A' was in the east near the valve tower bridge with ‘Byewash B' at the dam's western end. A byewash was merely an overflow, which controlled how and where excess water flowed over the dam crest. Their major benefit was that they prevented scouring of the dam's vital earth filling. The little bridge over Byewash A features in many early photos of the dam, and a spillway from this overflow, comprising of four distinct construction types, remains. A timber section of this spillway has been replaced in the past, but the current timber section is sympathetic to the original design. A precast concrete pipe and concrete culvert have replaced other parts of this spillway. The western spillway, understood to have been entirely comprised of timber, was replaced by concrete works in the 1940s.
Also seen in early photos of the dam (at least by 1880) are two buildings, the boat shed and caretaker's cottage. The boat shed was built just upstream of the dam. The building can just be seen in the photo of the dam about to be filled, suggesting that it was built at the same time as the dam itself (between 18761878). The Sanctuary's interpretation suggests that the building was erected to house the Governor General's boat with the reservoir stocked with trout for him to fish in. By the 1920s it was described as a tool shed and it has also been an office and store. Buttresses were added on the south side, reputedly added after it was blown over in a gale in the 1920s. Until the 1990s it was partitioned into two rooms at which time it was restored, and given a new foundation. The caretaker's cottage was just downstream of the dam (it was where the car park is now), but was removed in 1959, presumably to make way for the contact tank, work on which started soon thereafter. Staff, numbering up to four caretakers, were thereafter accommodated in the nearby streets.
The Karori Reservoir, as the area became known, became a destination for tourists and a subject of many commercial postcard photographs. It was intended from the start to be an attractive recreational facility, with the downstream slope of the dam grassed, trees planted and boating permitted (initially).
Low pressure from Karori water and an inadequate supply led to other water supply dams being constructed to supply Wellington, starting with the first Wainuiomata dam in 1884. After this, comparisons were able to be made with Karori water which at times was deemed ‘inferior in quality' and colour. Some of this was due to the catchment around the Karori reservoir being used by a dairy farm and sheep run, which was described as ‘thoroughly dirty'. Only when a second dam was also contemplated in this catchment, in 1906, did the city acquire the catchment (mostly from farmer AB Fitchett) and prohibited any farming or hunting near its shores.
The second or upper Karori dam was built in 1908. Its only effect on the original dam was a change in name, to the Lower Karori Dam. Functionally it augmented the capacity of the lower dam by keeping it full rather than supplying water to users directly. A small pipe (8inch, 200mm) was laid from the upper dam to bypass the lower dam, running down the eastern or right bank. This required a break pressure tank being built at the lower dam (to reduce the pressure of water before it entered the water supply system). Modifications were required when a major new source of water, from the Orongorongo River, was brought to Karori in 1926. The 21inch pipe for it came up to the dam over the eastern end, and required an outlet be built by the bridge to the valve tower. A ceremony here on 23 December 1926 officially turned on water from the Orongorongo project. The OrongorongotoKarori main became known as the ‘OK' main and significantly boosted the water coming through the Karori dam facilities. Other aspects of renewal of the dam's facilities occurred in the mid 1920s. Two plans dating from 1924 show a new bridge to the valve tower and a culvert replacing the small bridge that carried the roadway over the eastern byewash.
The quality of water continued to get more attention. The city's first chlorination plant was begun at the Lower Karori Dam in 1929. The addition of chlorine in safe quantities killed off micro organisms that could carry disease and taint the taste and smell of water. A plan shows a small chlorination plant and bottle store up on the dam crest, at its eastern end. A leak in the dam was fixed in 1930, in which a small section of puddle clay core about 12ft (3.6m) deep and similar width was replaced.
The distributing basin at the head of Aro Valley appears to have been decommissioned in approximately 1929 with correspondence from concerned rate payers regarding damage to trees and the danger of the reservoir to children appearing from this date, suggesting that the area was no longer being actively managed. The pressure of the water's flow was instead controlled via a breakpressure tank. The distributing basin was not filled in at this time and subsequently in 1942 the local fire service sent a deputation to the Mayor asking that it be kept filled with water as an auxiliary fire supply. After an inspection of the basin was conducted and repairs in concrete to a crack in the floor made this proposal was agreed with the proviso that the fire service could fill it with no more than 8ft of water (approximately 330,000 gallons) and a fire plug was cut in to enable this. It is not yet known when it stopped being used for this purpose but it was finally filled in 1963 using spoil from the Terrace parking building and the vicinity to make way for a yard storing council pipes. It continues to be used for this purpose.
In 1935 a local pumping station was built at the Karori dam to feed Karori users (no doubt required by the exceptional height above sea level of the Karori service reservoir, 844ft (257m) up Wrights Hill Road). This 1935 pumping station is the only ancillary structure (apart from the caretaker's cottage and the 1929 chlorination plant and bottle store) to have since been removed. It was a building of approximately 8m x 4m, of timber construction on a concrete foundation (with a smaller valve out house immediately to its north). These were sighted to the north of and below the level of the northern tunnel exit, and beside the eastern spillway's confluence with the Kaiwharawhara stream. After the larger pumping station was built in the 1950s for the Kaitoke scheme this pumping station was decommissioned. The exact date of its demolition is not known, but its foundation can still be seen.
The catchment feeding the Karori dams was augmented in 1945 by pumping water from Long Gully, a branch of the South Karori Stream, over a ridge behind the upper Karori Dam. This supply was discontinued when another major source, the Hutt River, was brought to Karori. Planning for this started in the 1940s, and was completed in 1957. The Hutt River or Kaitoke system was another runoftheriver intake (like that on the Orongorongo River) and used the Karori dams for its storage. It also introduced a backpumping capacity for when the river water was too low or turgid to be drawn, and so a large pumphouse was built at Karori in 1956, below the Lower Karori Dam. This allowed water to be pumped back up the 30inch pipes to the Hutt River, supplying users en route. In preparation for the arrival of the Kaitoke supply a long tunnel was built in the late 1940s in the rock beyond the western side of the dam to allow the water to be introduced well up the lake. Later another pipe introduced water from Kaitoke directly into the lower Karori reservoir, via a 30inch pipe laid over the dam crest, by the western byewash. The long tunnel was used as a bypass tunnel allowing untreated water from the Upper Karori Dam to discharge into the stream below.
The 1950s work modified the area downstream of the dam considerably. Within a few years several new buildings and structures were added, and the ground significantly recontoured for their platforms and access roads. Another tunnel was driven from behind pump house to the existing tunnel intersection under the carpark.
In the 1950s a numbers of dwellings for water supply workers were also added to waterworks reserve in the area. A letter from the City Engineer to the Town Clerk at the time of erecting these dwellings notes that notes that it was ‘desirable to house waterworks employees in small groups in locations preferably on waterworks property where best use can be made of existing transport and telephones and where they can assist in trespass and vandalism'. Three of these dwellings, two built in 1954 and one in 1956, were situated off Disley Street above where the tunnel from 1872 runs beneath ground (on Pt Sec 1 Upper Kaiwharawhara District marked A on SO 32281 and Pt Sec 10 Owhiro District marked A on SO 32922). In 1969 garages were added to two of the buildings off Disley Street. The Disley Street dwellings and garages remain on this site today.
By April 1957 another ancillary structure was added at Lower Karori Dam. This is the small valve house on the 30inch main from Kaitoke (not to be confused with the valve tower and its neogothic roof). The test equipment could test the water for treatment purposes, looking at its alkalinity, colour and turbidity.
A circular 2.1megalitre contact tank was built at Karori in 1962. This was part of a new chemical treatment process at Karori (and other dams), allowing the chlorine 30minutes contact time with the water before it was reticulated. Fluoride was also added. After the dam was decommissioned in 1997 this tank retained a role as a service reservoir for the Aro area, and is known as the Aro Reservoir.
Also built as part of this treatment plant was the chlorine store (by the car park, and now known as the ‘Giraffe house' because of its two tall doors (about 4m high). When built in 1962 it replaced two smaller stores for chlorine bottles (each 1.8m square) sited on the dam crest by the boathouse. The new building housed taller and very heavy pressurised bottles of chlorine gas and required a gantry crane to lift them from delivery trucks into the store. Equipment in the store could also weigh the bottles, to see how full they were.
The backpumping capacity at Karori was increased in 1968, with the addition of a third pump. This pump house was extended at this time, with a 5x6m annex to the east. Another annex to the south, 5.5m square, was added in 1993 when the chlorination dosing system was changed to the ‘hypo' system. The dam's role in backpumping was lessened with the commissioning of pumping stations at Haywards in 1971, Te Marua in 1985 and Ngauranga in 1992. This chlorine annex added to the pump house was the last major modification to the Karori dam area until its stored water stopped being used for water supply in 1997. The Karori dam water supply functions were replaced with a water storage reservoir commissioned in 1997 above Ngauranga Gorge and the water supply pumping station and pipeline commissioned in 1992 in Ngauranga Gorge that linked the Wainuiomata water supply pipeline to the Te Marua water supply pipeline. The quality of water from Te Marua and Wainuiomata was superior to that from Karori. The dam has not been decommissioned as such, as it is still retaining water, however all Greater Wellington's functional pipelines were disconnected from the dam in 2000.
With a lessening role in supplying water, the Karori waterworks reserve was gifted back to Wellington City Council for the Karori Wildlife Sanctuary in July 2004. The Karori Wildlife Sanctuary ‘a worldfirst conservation attraction' that provides ‘a safe haven for endangered native birds and other wildlife' is run by a charitable community trust which was founded in 1995. The Lower Karori Dam forms an integral part of Karori Wildlife Sanctuary's visitor experiences.
In June 2007 the Prime Minister, Helen Clark announced that the Karori Wildlife Sanctuary had been granted $6.5 million dollars from the Significant CommunityBased Projects Fund towards a new visitor and education centre. As a result of this redevelopment some of the buildings associated with the more recent history of the dam will be demolished and the eastern spillway will be modified. However it is also anticipated that the new centre will increase visitor numbers to the Sanctuary, and by default the dams. In 200607 the Sanctuary received over 64,000 visits. A press release from the Sanctuary at the time of the visitor and education centre announcement notes that it is estimated the Visitor and Education Centre will attract 190,000 visitors a year.
The pump house is also in the process of being decommissioned by Greater Wellington. A new pump house was built (away from the fault line) on Chaytor St opposite Appleton Park, and partly commissioned in August 2006. When issues with the pumps intended for Kelburn users are fixed, this will be fully commissioned and the 1950s pump house below Karori dam will stop work finally, after half a century's service.
At its peak in the 1950-70s, the Karori Dam was the heart of a water supply network stretching as far north as Kaitoke beyond Upper Hutt (57km away), as far east as the Orongorongo River (in the Wainuiomata catchment) and supplied users as far north as Porirua with water of the highest quality. Karori remained the terminus for the much of the supply to Wellington, even when other sources were added up to the 1970s. Though water from neither Karori dam enters the watersupply system, water from other sources still flows under the Karori dam (the OK main pipes were relined in 200001) and out through the 1872 tunnel, which is still in use.
