The Waters of Table Mountain - Part 3

Streams and ravines 

It is one of the many joys of hiking Table Mountain to chance upon a burbling stream, a secluded pool or a cascade pattering down on solid rock from up high. The atmosphere that these features create acts as an effective medium through which we connect with nature. Few sounds instil as much serenity as the trickle of water on a mountainside or the clicking of frogs beside a backwater pool. Add to that the geological drama and floral extravaganza on display on Table Mountain, and you understand something of the mountain’s appeal.

Table Mountain’s waterways are in a constant state of fluctuation. Parched streambeds in summer transform into gushing torrents in winter. Few perennial streams occur on the mountain. Some of the ravines that carry water throughout the year include Platteklip Gorge (lower reaches only), Disa Gorge, Window Gorge and Skeleton Gorge. Even these often end up half-dry by late summer (February / March), their water reduced to an underground seep, only to burst into life again in June at the onset of winter. Some hiking routes leading up ravines become treacherous and nigh on impassable during the winter months, when sections are transformed into foaming streams.  Skeleton Gorge is such a route; graded A (technically the easiest grade), it feels more like a C-grade after a winter storm.

Mountains are known to be the birthplace of rivers. Table Mountain with its flat summit catches a lot of rain that drains down the many ravines dissecting the mountain. The mountain’s proximity to the sea barely allows its streams to grow into fully-fledged rivers. During the winter months, a single deluge can transform a placid stream into a raging torrent. Runoff is fast and furious due to the steep terrain, and there is little water retention; less so in summer, when the mountain is parched and acts as a sponge. Hiking Table Mountain in winter, one has the privilege of tracing streams right to their source, where they start their journey to the sea as seeps near the summit. Hundreds of seeps merge to form a stream, in turn joining other streams and swelling into torrents that thunder down the mountain. 

I often get asked about waterfalls on Table Mountain. These only really come into being during winter, when Table Mountain receives 70% of its annual rainfall. Well-known and conspicuous waterfalls include Hell’s Gates in Disa Gorge, the cataract in Skeleton Gorge at its junction with the Contour Path, Blinkwater waterfall, Grassy waterfall and Fountain waterfall, taking the names of the ravines in which they occur. Grassy waterfall must rank as one of the longest and strongest on the mountain, as it can easily be seen from a kilometer away, appearing as a white ribbon on the eastern slopes. Located high up the mountain in an inaccessible area, no one bothers to make the arduous trek to its base. (Watch this space: I plan to make the trek this winter and get some pictures)

A detail often remarked on about Table Mountain’s water is its amber color. Streams in the Western Cape are often referred to as blackwater streams, as the amber color takes on a black appearance in deep pools. The color is caused by chemical compounds, called polyphenols, leaching out from dead leaves. Plants on Table Mountain produce polyphenols as defense against herbivores, as it makes the leaves unpalatable. The presence of polyphenols only affects the water’s color, not the taste. And it’s perfectly safe to drink. Some streams on Table Mountain filters through clay soils, allowing the polyphenols to bond chemically with the surfaces of the clay granules, ridding the water of its amber hue. A good example is the Platteklip Stream, whose water emerges crystal-clear at a point just above the Contour Path in Platteklip Gorge.

Which brings us to the existence of subterranean streams on Table Mountain. I know of three places on the mountain where water mysteriously emerges or disappears; and no doubt more such places exist. One is the Platteklip Stream, mentioned above, lifeblood of Cape Town up until the 1880s. Obvious along the gorge’s lower reaches, the stream disappears a short distance above the Contour Path, never to be seen again. Even in high winter, with water flowing down all the ravines on the mountain, the middle and upper reaches of Platteklip Gorge remain virtually waterless. In the Valley of Isolation on the Twelve Apostles, a small cave allows one to see water flowing through the mountain – east to west – its outflow still a mystery. 

Another unique aspect of Table Mountain’s water is its presence on the upper plateau (the actual tabletop). For much of the year, large parts of the summit plateau are waterlogged. The eastern table is known for its bogs, and even features a lakelet, or small natural pool. About a meter deep during winter, it gets topped up by the moisture-laden Tablecloth cloud-formation during the long, dry summer months, when at times it dwindles to barely more than a marsh pit. As for swimming possibilities, it’s too cold to enjoy in winter and too shallow in summer, but fun and invigorating to wallow in on sultry spring days, when the water level is fairly high.

Last but not least are the springs of Table Mountain – those rare places where a seep or drip can be found even in summer, when the mountain bakes under a torrid sun and the heat shimmers off dust-dry watercourses. Several springs exist on Table Mountain – and no one can profess to know the whereabouts of them all. Back in the early days of mountaineering, hikers and climbers relied on springs for their water supply. In the 1940s and 1950s, some were graced with small ponds to pool the water for convenient drinking. Nowadays, hikers and climbers carry their own water, only resorting to springs when their own supply run dry. 

The history of Cape Town and its people is entwined in the streams that flow off Table Mountain. The city has the mountain to thank for its existence. As hikers and climbers, we continue to draw sustenance from Table Mountain’s streams, sometimes to quench a thirst or revive the body, but more often to drink in the vitality and peace it brings to the surroundings.

The Waters of Table Mountain - Part 2

Table Mountain’s reservoirs

Up until the mid 1880s, Cape Town relied on a single Table Mountain stream for its water supply: the Varsche River, a confluence of three smaller streams that drained the northern slopes and the Saddle (the neck linking Devil’s Peak with Table Mountain). The drought of 1880 drove home to the town-planners the stark reality that the city needed more water, and fast. John Gamble, incumbent Colonial Hydraulic Engineer, revived an earlier idea that a tunnel be driven through the Twelve Apostles to capture the water of the Disa River, a strong perennial stream that drained much of the Table Mountain massif. 

Work on the 700-meter tunnel started in 1887, as did the construction of a pipeline several kilometres long, stretching from the tunnel exit in Slangolie Ravine on the Twelve Apostles to the Molteno Reservoir in the city center. But even before the tunnel’s completion, it became clear that more should be done to secure a steady supply of water. That’s when they decided to dam the Disa River.

Work on the Woodhead Reservoir began in 1890. Located on the Back Table – also known as the lower plateau, an extensive and undulating area behind (south of) the tabletop summit of Table Mountain, or upper plateau, and about 300 meters (1000 feet) lower down – the reservoir spanned the Disa Gorge along its middle stretches. The construction was a major undertaking: long lines of porters toiled up Kasteelspoort, a ravine on the Twelve Apostles that offered easy access, laden with building material. To assist in the task, a small open-skip, steam-driven cable car was strung up in 1893, with its lower terminus above Camps Bay and its upper terminus 650 meters higher on the northern edge of Postern Buttress. From here a small locomotive – carried piecemeal up the mountain – conveyed material to the construction site about two kilometers away. A small town sprung up on the summit, complete with its own bank, post office and shop. The dam wall, constructed from sandstone blocks quarried on the mountain, measured 252 meters across and 44 meters high, with a base thickness of 19 meters tapering to 3 meters at the top. But in 1898, only a year after its completion, it became apparent that the city’s water demand had outstripped supply – again. 

A second reservoir was promptly built a little upstream from the first, completed in 1904. Named the Hely-Hutchinson, its masonry wall measured 528 meters, while its water surface covered an area of 16 hectares. During all this time, the Wynberg municipality (a suburb of Cape Town and a separate municipality) had been labouring away at its own reservoirs on the mountain, three in total (Victoria, Alexandra and De Villiers), located further south on the Back Table, tapping a tributary of the Disa River. 

But Cape Town’s water woes did not end there. In 1905, the city became aware that demand yet again threatened to outstrip supply. After considering several alternatives and ideas, the city decided that Table Mountain’s water was utilized to the hilt and that more dam-building would not solve the problem. Instead, it undertook to obtain water from the Steenbras Dam, situated about 80 kilometers outside Cape Town. 

This set the tone for future efforts to increase Cape Town’s water supply. The chain of mountain ranges northeast of Cape Town stretching from Somerset West in the south to Ceres in the north offered extensive catchment areas that awaited exploitation.

Currently, Cape Town has six supply dams, the most recent addition being the Berg River Dam, opened in March 2009 and boosting the city’s water supply by a whopping 20%.

Table Mountain’s reservoirs are still in use, contributing around 5% of the overall supply. In the 1950s, the Woodhead Tunnel began to cave in and a new tunnel was built a few hundred meters to the north, exiting on Woody Buttress on the Twelve Apostles. This enabled the Woodhead and Hely-Hutchinson reservoirs to remain in use. 

Nowadays, all that remain of the construction site are bits and pieces of the upper cable car station, a few concrete floors where the village once stood and a few huts, one of which belongs to the Mountain Club of South Africa and another to the Cape Province Mountain Club. A third hut serves as a museum – the Waterworks Museum – where the old locomotive is on display along with various artifacts used during the construction. The museum and old cable car station makes for interesting asides when hiking in the vicinity.

(Part 3 of The Waters of Table Mountain takes a closer look at the streams on Table Mountain from a hiker’s perspective.)

The Waters of Table Mountain - Part 1

In my next three blogs I will briefly trace the story of Table Mountain’s water, from the role it played in the establishment of Cape Town to its coming of age as a city. The final instalment will deal with the occurrence of streams on Table Mountain, their significance to hikers and the part they play in shaping the mountain. 

Part 1: Early Days

To the Cape’s indigenous people – the Khoi-Khoi pastoralists and the San hunter-gatherers – the area now occupied by central Cape Town was known as Camissa, Place of Sweet Water, as anyone who has drunk from Table Mountain’s streams would attest to. When Portuguese explorer, Antonio de Saldanha, climbed Table Mountain in 1503 (the first European to do so) to get his bearings, he was delighted to find a strong stream flowing down the ravine (now known as Platteklip Gorge) by which he had gained the summit, more than enough to water his fleet. The bay at the foot of the mountain, present-day Table Bay, became known as Aguada de Saldanha, Watering Place of De Saldanha. Dutchman Wouter Schouten, who tasted the water on the mountain in 1665, had this to say about it: “We found it quite sweet and exceptionally pleasant in taste... Our heavenly liquid now tasted better than ordinarily does the most exquisite drink in the world.”

It was the water running down Platteklip Gorge that induced the Dutch to settle at the foot of the mountain in 1652, building the first structures of an outpost that became the bustling metropolis of Cape Town, Mother City to South Africa. Table Mountain gave rise to five streams, known by the Dutch as the Varsche (Fresh) River, draining the north face (front); the Liesbeek River, rising on the eastern slopes; the Diep and Spaanschemat Rivers, both flowing southeast; and the Disa River, emptying in Hout Bay south of the mountain. It was the Varsche River that sustained the Dutch settlement. Carrying the waters of the Platteklip Stream – and bolstered by two tributary streams, the Silver Stream and Capel Sluyt – the Varsche was soon channelled by the Dutch to water their fruit and vegetable gardens. 

As the settlement grew, so did its water needs. By 1849, water was so scarce that Cape Town’s street services ground to a standstill. Three reservoirs were built – in 1851, 1860 and 1881 respectively; the latter still in use – to solve the city’s water problems, but they failed to quench the thirst of the ever-increasing population. Desperate times called for desperate measures, and in the early 1880s the decision was reached to drive a tunnel through the Twelve Apostles to tap the waters of the Disa River, whose huge catchment ensured a perennial and substantial supply. 

As can be seen from the above, the streams flowing off Table Mountain, especially the Varsche River, played a central role in the birth and development of Cape Town. Sadly, the city has shunned its erstwhile lifeblood. The last remaining Dutch canal, the Heerengracht, was covered in the late 1850s; and the outbreak of the Bubonic Plague in 1901 saw the last stretch of open watercourse go underground, never to be seen again. the Varsche River now flows beneath the city, confined to stormwater tunnels and drains, its sweet water going to waste in the sea. A new initiative is currently underway to put the water to use. 

The Varsche’s main source, the Platteklip Stream, still cascades down the lower stretches of Platteklip Gorge (it being subterranean higher up) above the city center and makes for an impressive sight when in full spate. It is one of only a handful perennial streams on the mountain, swelling to a torrent after winter rains and dwindling to a seep in late summer, when its crystalline waters serves as a welcome refreshment to many an overheated hiker.

(Part 2 deals with the building of the reservoirs on top of the mountain in the 1890s.)

'The one who is afraid of the sun'

I’m not really into frogs. I love their croaking – especially in misty conditions on the mountain, when it lends an air of mystery to the landscape – but otherwise I am not particularly impressed by them. That all changes when it comes to Heleophryne rosei, commonly known as the Table Mountain ghost frog, one of 19 frog and toad species on the mountain.

So what makes the ghost frog so special? Primarily, its distribution: it lives only in the swift-flowing sections of seven perennial streams on Table Mountain (all on the south and east side), nowhere else on earth. That’s an area of about eight square kilometres. One of only two vertebrates endemic to the Cape Peninsula (the other also a frog), the ghost frog can truly be called a child of Table Mountain.

Heleophryne (Latin for ‘the one who is afraid of the sun’) rosei is one of the most ancient frog species, having split off from its closest ancestors more than 160 million years ago. Its solitary evolution on Table Mountain spans millions of years and gave it the niche habitat of swift-flowing streams by endowing it with suction pads on their toes, tiny skin projections that grip like Velcro, flattened bodies and highly webbed feet. Even the tadpoles are adapted to life in the fast lane, possessing sucker-like mouthparts that prevent them from being swept away by the current.

One of the coolest things about ghost frogs is their translucent belly through which the innards can be seen. This together with its scarcity and secretive nature accounts for its name. In fact, you’re almost more likely to come across a real ghost on Table Mountain than one of these guys. Two decades of hiking the mountain and I’ve only ever chanced upon one. They spend much of the day underwater, ensconced in crevices, only emerging at night to feed on insects.

So how will you recognize one? If you find yourself along a fast-flowing stream on the south or east side of Table Mountain at dusk – or at night with a headlamp – and you come across a frog five to six centimeters long with enlarged toes and a striking skin coloration (pale green with purple spots) perched streamside on a mossy rock, then you’re most likely looking at a ghost frog. Congratulations. However, non-breeding adults occasionally do stray from streams and venture into bogs and caves.

Sadly, the ghost frog is set to become even more elusive, and might even face total extinction. Tadpole numbers in Skeleton Gorge (one of its habitats) have dropped by an estimated 50% since 1980. Not surprising that it’s listed as Critically Endangered. With an area occupancy of less than 10 square kilometers and a continuing decline in the extent and quality of its habitat, extinction is a very real possibility. In fact, it has already become extinct in some parts of the mountain. The main threats are the spread of invasive alien (non-indigenous) vegetation, frequent fires and reservoirs (affect the consistency of stream-flow). Furthermore, poor forestry practices also contribute to the clogging of streams.

On a brighter note, Table Mountain National Parks is committed to the eradication of alien plants on the mountain – an ongoing programme that will benefit not only the ghost frog, but many other native plant and animal species.

We at Hike Table Mountain actively involve ourselves in the fight against aliens (of the terrestrial kind!) through the cutting down of cluster-pines (saplings), one of the most invasive aliens on the mountain. Please feel free to contact us should you wish to join our next outing.