If you're travelling on
the B1 road about 20km north of Tsumeb on the western side you will
see Lake Otjikoto. Its only a few meters from the main road and it's a
well worth while visit. The owners have geared-up for tourism, so
additional to the attraction of Lake Otjikoto there is a menagerie,
shop, restaurant, and a good selection of Stromatolites.
The Formation:
The deep turquoise waters of the lake add a bit of mystery. It's only when
you realize that the whole surrounding area of ground is acting as a roof
covering a massive underground Karst Lake, and that the area where the lake is,
being about the size of a football field is just a small section of the roof
that collapsed in, that you begin to wonder when the next 'accident' will occur.
The above right is an impression of the shape of the
known area of the lake bed. It is over 50m from the lake surface to
the peak of the debris cone that was formed by the collapse.
The
triangular area of Grootfontein -
Otavi -
Tsumeb comprises of dolomite rock
some 700 million years old. There are many occurrences where the ground
water has percolated through fractures within the rock formations. The
carbonic acid in the water over many years dissolves the rock and forms
cavities. Gradually these form to become large underground caves filled
with water, as 'Karsts'. The on-going dissolution of the rock eventually
causes the roof of the Karst Cave to collapse. The conical debris mound
that lays on the lake bed is referred to as a Dolinen. Both Otjikoto and Guinas
have excellent examples of Dolinen.
The Size: The visible part of the 'lake' is +-100m in diameter
having a surface area of 7075 sq m. The depth varies from 62m at the
side, 7m in the centre and in some places leading off from the side
depths of 100m have been recorded. The dimensions and size of the
underground cave is not known, but it is thought that the water storage
area is 4,000,000 cubic meters of which the Government allow 1,3 million
cubic meter to be extracted per year. Ancient Karst lakes, such as this, are
often just part of a huge underground water system interconnecting with
other 'cave' lakes, some of which may also have a section of the roof that
has collapsed-in, such as Lake Guinas, which is about 20km distance from
Otjikoto.
The Discoverers: The first Europeans to
'discover' Lake Otjikoto (in 1851) were Sir Francis Galton - Fellow
of the Royal Society and his English-Swedish companion Charles John Andersson - Galton wrote of their experiences at lake Otjikoto in
his book, "The Narrative of an Explorer in Tropical Southern Africa"
that was published in 1853.
"May 26th: Without the least warning we came
suddenly upon that remarkable tarn, Otchikoto. It is a deep
bucket-shaped hole, exactly like Orujo, but far larger, for it is
400 feet across; deep down below us lay a placid sheet of water,
which I plumbed leaning over from a cliff above, to the enormous
depth of 180 feet, the same depth within five or six feet at four
different points of its circumference. The water could be reached by
a couple of broken foot-paths, to the top of one of which the oxen
were driven to drink out of a trough, and a line of men handed up
bambooses of water from one to another to fill it. There were small
fish in the water; it is curious how they got there. I was told that
fish were also to be found in the fountain head of Otjironjuba, but
I did not see them. There were infinite superstitions about
Ochjikoto, the chief of which was, that no living thing ever got
into it and could come out again. However, John Allen, Andersson,
and myself, dispelled that illusion from the savage mind, by
stripping and swimming all about it, under the astonished gaze not
only of the whole caravan, but also of quantities of Bushmen who
lived about the place, and who came to greet the Ovampo, with whom
they are the best of terms.
Although the Ovampo live on the borders of a great
river, yet none of them had ever been seen swimming. It appeared
that alligators were so numerous that the natives feared to venture
in. Chik had been extremely friendly up to the present time, but now
began to look with some suspicion upon us; the fact of our having
swum about Otchikoto alarmed him - it looked like magic. Again my
Damaras were always teasing the others by saying that we were
cleverer than the Ovampo - a fact which these would not admit; but
now it was proved beyond doubt, and the whole eighty-six females
sang songs about us; one matron improvised, and all the others
joined in a shrill chorus, like "tirri-tirri-tirri." The self esteem
of the Ovampo had certainly been wounded. Chik at first ridiculed
guns. He had seen guns in Benguela, but they must have been
worthless affairs, and badly handled, for he laughed at any
comparison between them and arrows; however, by degrees he became
frightened at seeing what they could really do. There was a duck
swimming about the water, not more than sixty yards off, but it
looked very much further, as things below one always do, and I shot
him very neatly with my little rifle: and again, the next day,
Andersson, was shooting some birds on the wing for specimens, and
Chik became so frightened that he would not pick them up. We had
great fun at Otchikoto; there was a cave there full of bats and
owls, which we swam to and explored. The place swarmed with doves,
and every now and then a white hawk swooped in amongst them. The
Bushmen captain fraternized with me, and we interchanged smiles and
small presents."
