Woodhead Reservoir carved in stone
Woodhead and Hely Hutchinson dams table mounatin

WOODHEAD DAM

 

History of water at the Cape since the European invasion

 

When the Dutch East India Company established the European colony that was to become Cape Town in 1652, the invaders drew water from the stream flowing down Table Mountain's Platteklip Gorge. They called it Varsche River. It provided the settlement and passing ships fresh drinking water.

Table Mountain, 1634 showing Platteklip stream flowing into Table Bay
Sketch of Table Mountain dated 1634 showing Platteklip Gorge & stream flowing into Table Bay

In 1660 Jan van Riebeeck, the governor, installed irrigation furrows, and dug deeper into the stream-bed. It soon became a canal, or a 'gracht' that flowed down to the Table Bay jetty.

 

There, a small dam was built to make it easier to fill water casks. Ten years later a cistern was constructed. Soon a network of canals crisscrossed the growing town, the remnants of which are still apparent in some Cape Town street names like 'Heerengracht' and 'Buitengracht.'

 

Windblown dust and dirt from the settlement rendered the water undrinkable. Willem Adrian van der Stel piped water from the foot of the mountain to a fountain in town. A well in Greenmarket Square augmented the town's water supply.  

 

With the 1806 onset of British rule a reservoir was built in Hof Street. It held 250 000 gallons (946 352 litres) Supply infrastructure grew with a main pipe down Long Street.  Water was also pumped from underground springs.  Most household water was carried from public fountains by slaves.  

 

By 1840, with Platteklip having dried up, a new reservoir was needed to harvest winter rain.  

 

Despite better understanding of the role of water-borne disease, the town by many accounts was filthy. Finances were not made available to curb the stench of open sewers and the illnesses that spread from them.  

 

In 1880 the 40 million gallon (150 million litres) Molteno Reservoir was completed. It remained empty while the region was gripped by drought. Water released to households came every second day for three hours.  Two years later when eventually the rains fell, the reservoir burst. The city's water supply remained in crisis.

 

Initial Plans for Woodhead Dam 

 

John Gamble, a young Oxford trained engineer was appointed to advise on irrigation and water supply in the colony.  He set up a system of weather stations and water gauges throughout the Cape. Identifying the back plateau of Table Mountain as the best catchment area, he planned to pipe water off it down through the western flank of the mountain known as the Twelve Apostles, and along the base into Cape Town city's Molteno Reservoir.

 

Gamble left the colony before action was taken. The plan was revived by Thomas Cairncross, the newly appointed City Engineer in 1891. Water from the Disa Riva, flowing from the Back Table, was diverted into the new Twelve Apostles pipe.  

Disa Stream, Table Mountain resevoirs view from Disa stream
Disa Stream flows into the Hely Hutchinson and Woodhead Dams

By the late 1880s it was realized that a dam would have to be built on the mountain to satisfy Cape Town's demand for water.  A young Scott, Thomas Stwart, the engineer behind several Cape water schemes, including a reservoir behind Table Mountain at Constantia Nek, was commissioned.

 

He planned to dam the Disa River that feeds the gorge river that flows into Hout Bay.    

 

View from Woodhead Dam into Disa Gorge
Disa Gorge

Construction of Woodhead Dam

 

Material was lugged from Kloof Nek along the Pipe Track. A cable way was rigged up Kasteelspoort to haul heavy gear, coal and cement that couldn't be taken up by porters scrambling up the ravine.

 

At the top rail tracks were installed to the building site.  Mules pulled laden trolleys along them. Accommodation for five hundred workers was set up, as well as a bank, post office and a football field. Scottish machinery, stonemasons and quarrymen were brought over as there had never been an undertaking of this sort done in South Africa. Local labourers who provided the basic grunt work found it difficult to understand their accent.    

 

In 1894 foundations deep into the mountain were excavated.  Sir John Woodhead, Cape Town's mayor laid the last stone in 1897.

Last Stone Laid at Woodhead Dam by John Woodhead 1897

More Dams for Cape Town needed

 

With Cape Town's booming population it was soon realized that a second dam would have to be built. Stewart regathered the team to build the Hely-Hutchinson (named after the governor of the Cape) and three smaller dams. Instead of mules, a locomotive was brought up and assembled, and called the Mount Meg. It is still on the mountain housed in the museum near the Hely-Hutchinson.     

 

The Hely-Hutchinson, after a delay because of the Anglo Boer War, was completed in 1904. It was already apparent that new far bigger dams, beyond the city, were now going to have to be built. 

MCSA Journal article: Woodhead Dam, Table Mountain
photo: MCSA Journal 1896, p.12. Article on Woodhead Dam.

Mountain Club of SA Journal article 1897

Wrtten text of Mountain Club of South Africa 1896 article about Woodhead Dam
Text of MSCA Journal 1896 p13, on Woodhead Dam

In 2008 the dam was included on the American Society of Civil Engineers list of Historic Civil Engineering Landmarks.

Worker adjusting the flow from the Woodhead Dam into Disa Gorge, 2017
Adjusting flow from Woodhead dam into Disa Gorge, 2017
mechanics on the dam wall of Woodhead Reservoir
Mechanism on the dam wall of Woodhead Reservoir

What lives in Table Mountain's Resevoirs?

The Woodhead Dam as well as other reservoirs and lakes in fynbos-land have little in the way of noticeable life.  

Tannin, and chemicals that make the fynbos unpleasant-smelling to browsing animals, leach from decomposing plants. That turns the mountain water acidic. The water in Table Mountain reservoirs is, says The Fynbos Guy, "basically, weak carbolic acid. There is freshwater life but it's highly specialised, with much lower biomass than 'normal' wetlands."

frog-in-Disa-Stream, Table Mountain National Park
Resident of Disa Stream, that feeds Hely-Hutchinson and Woodhead Dams
Woodhead Dam, an International Historic Civil Engineering Landmark; photograph taken from Hely-Hutchinson Dam wall. Machinery originally used in it's construction visible, right, at sight of small museum.
Woodhead Dam from Hely-Hutchinson Dam wall. Machinery originally used in it's construction visible, right, at sight of small museum.

Material for this post comes from the book Megastructures and Masterminds  by Tony Murray