How much water is stored in our dams?

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A very empty Theewaterskloof Dam in 1997.  This dam has filled only three times since it was built.

Cape Town has no more dams that can possibly be built.  Our rivers are damned.

The title of this article may very well be titled: where does all of our water come from?  This question is posed as I hear it said all too often that the City should build more dams.  Well there are no more dams that can possibly be built.  And it is no use raising dam levels either.

Cape Town has six major storage dams.  These are in order of size: Theewaterskloof 480,  Voëlvlei  160,  Berg River 120, Wemmershoek 70, and the two dams on the Steenbras River Upper and Lower of 33 and 31.  These numbers after each dam refers to million kilolitres (cubic metres) of water thus Theewaterskloof is 480 000 000 kilolitres and is bigger than all of the rest of the dams put together, yet the yield is relatively small in that it seldom fills.  It should be noted that there are several dams on the Table Mountain area amounting to .3 of 1% yield to the city and not taken very seriously in terms of volumes, the levels are not reported very widely.

The Table mountain dams, 90 years ago accounted for all of the needs of Cape Town.  After the last of them was built in 1927, the city guarded water supply incredible jealously, making it illegal to have and fill a “water butt”.  The excuse they used was that these bred mosquitoes, and perhaps they were right, but they lied about the real reason which was to maximize their new facility and perish the thought of using water from one’s own water tank.  And then in 1953, the first large dam was built – Steenbras Dam, which was heralded as water for the future, and no more dams would be needed in the foreseeable future.  That is quite silly really as all of the rest of the dams (excepting Berg River) were built in the next 30 years and still we have run short of stored water!  That is categorically not true either as over the past two years thanks to “day zero” Capetonians have reduced demand for water to less than a quarter compared with what they were using in 1996.  This proves unequivocally that the best way to create more water in the dams is to use less, or put in another way: the comparison between supply management and demand management is that demand management works far better.

It was not very funny at all when just before the turn of the century,  Cape Town City Council was forced to implement a demand management policy – something they really didn’t want to do, and part of the order from the commander-in-chief   Kader Asmal the then Minister of Water Affairs  was that the city must appoint a Demand Management Officer.  They complied because they wanted the Department of Water Affairs to approve of the building of Skuifraam Dam later to be renamed as the Berg River Dam.  Well the trick up the sleeves of the city when appointing Charles Chapman was to muzzle him.  He was not allowed to speak to the media.  That was fine really as anything he wanted to say he simply mentioned this to me, and I spoke or wrote to the media and the knowledge was made public.  It did not take long for the Council to cotton on to what was going on, and in a response to my comment, I was vilified by Cllr. Davie Erleigh (the one who jumped parties) who claimed that “Mr. Taylor has an agenda” whatever that was supposed to mean and about which he did not elaborate.

The point is however that the city does not like demand management of water and every time they are forced to implement this as a means to stem supply, they say they lose revenue which thanks to new tariffs is quite untrue.  After all if the city has belt and braces both the supply of water and unfettered access to new and or change tariffs, then any losses of revenue can be made up very quickly which is indeed what they did.  The fact that they may lose political support through these new tariffs remains to be seen.  Though judging by the losses in the May 2019 the DA lost ground, a portent of things to come?

A vast dessert with a mirage in the distance?  No, just an empty Theewaterskloof dam.  This area is very windy.  Would it not make sense to build a gigantic wind farm over the vast surface area of the dam while we have a chance in that the dam is empty?

Some people have called for dredging our dams.  It is true that the vast surface area covered by the dam is very shallow, but to remove millions of cubic metres of soil and rock is highly costly and totally impractical.

Jeremy Westgarth-Taylor

Water Rhapsody

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