How much water is stored in our dams?

How much water is stored in our dams?

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

Cost of Desalination of Sea Water in Cape Town.

Cost of Desalination of Sea Water in Cape Town.

Desalination plant Picture this scar between your home and the sea.

While doing some work for an informal settlement in Stellenbosch I came across some fantastic research.  A Zimbabwean woman Rejoice Melisa doing her Ph.D at Stellenbosch on treatment of Acid Mine Drainage (AMD) she had concentrated her efforts on producing desalinated water from this toxic water not by Reverse Osmosis (RO) but by freezing the water to create ice which is removed as a slurry in the form of pure but frozen  water.

The freezing process of sea water too removes the salt.  When I queried the energy cost of the process of purifying the water through this desalination process, she boldly informed me that this was a seventh of the cost of flash evaporation and condensation.  I was not provided with any details of the comparison of the desalination cost of her freezing and thawing method against the cost of RO.

MONEY

When one considers the cost of building a RO plant, turn your eyeballs into Dollar signs.  Based on other plants globally for the supply of water to just over a million people the cost of building that size of RO plant will be upwards of 120 billion Rand.  That is just the start!  The cost of electricity is around 10 kilowatt hours per kilolitre.  This means that for Cape Town  at say 200 000 kilolitres per day the electricity energy would be 2 million kilowatt hours per day or 2000 megawatts, the size of a medium sized power station.  Clearly we do not have the money  in the form of capital or the energy from ESKOM for this.

We await a court ruling as to whether Cape Town City will be allowed to get some power from IPP’s (Independent Power Producers).  If not then please abandon all prospects of building a desalination plant in Cape Town.

This though is only the money.  What about environmental concerns as well as history in Cape Town of desalination plants.  What have we learnt?

Cape Town has built four such plants, only small ones, but they wanted and tried to build more but were stopped from doing so as those living nearby objected strongly to this and simply asked to see the EIA (Environmental Impact Assessment) of which of course there was a blissful ignorance.  In other words no such impact assessment was carried out.

Just as well for us that the City did not know what they were letting themselves in for by only having four built for many reasons but the best ones are these.

  • Day Zero never happened. The power of demand management through whatever means saw Cape Town through.
  • All of the desalination plants that were completed ceased to work. This was for various reasons but chiefly some failed thanks to an algal bloom in the water, and the one in the Waterfront found that there was too much sewerage effluent from the Citie’s own pumped outfall sewerage lines for them to cope.*
  • The Department of Water Affairs gave them a licence for only three years for these desalination plants and time is running out.
  • Every one of the temporary desalination plants built in the drought in the Garden Route area have all been abandoned and are now dysfunctional. Cape Town is not alone in this, but have we not learnt our lesson?

It was fascinating to hear how the Mayor – now Minister of Public Works boasted about how a well-run city will “never run out of water”.  She was right of course but it was more thanks to a very diligent and compliant population than from the City.  The citizens came to the party big time.  Every house I visit still today has grey water buckets for flushing toilets.  If ever I requested to use the toilet, I would be told sternly “not to flush” which was one step further yet in the old adage “if its yellow let it mellow, and if its brown flush it down”.  That used to be using municipal water , but now the flush is done with grey water.  In this line, I came across a very endearing ditty: “in this land of sea and sun, we do not flush for a number one”

Now we have Councillor Xanthea Limburg promising that we will get permanent desalination plants.  Best of luck Councillor, but I don’t know where you are going with this given our history of

Rather like energy, those ways that make lots of money (water and energy) they want their pound of flesh.  On this topic they have turned very nasty if one uses too little water or energy.  These two however are inextricably linked.

Water and Energy are inextricable linked.

Environment.

Environmentally, desalination of sea water is a long fuse but  big explosion.  Those in the Mediterranean and around the Arabian Peninsula all pour brine into the seas which have no current action to remove the brine and mix this into an ocean.  The brine is super saline water that needs to be discarded, and the pure water is the water that is used in the pipelines for drinking purposes. Even in fast moving current action, the brine is denser than sea water and sinks to the bottom of the ocean and fills undersea valleys where everything will eventually die forming new desserts under the sea.

If the energy for desalination in South Africa must come from far afield as the coal powered power stations in Mpumalanga and or near the Botswana border, the amount of carbon dioxide produced only to make water will be an ironic joke.  If however the city is able to persuade ESKOM to allow them to buy clean energy which ESKOM does not supply, then it may start to make sense even though very little.

To compare costly desalinated water at say at cheapest R30 per kilolitre for the City Councial and deliver this water at present rates of under R20 per kilolitre makes no sense whatsoever.

*Cape Town City put out the specifications for the temporary desalination plants.  The specification read that there would be a variance of 10% in water quality.  It was found that the quality varied by 400% causing the contractors to change filter cartridges every 8 hours instead of every 2 months.  Naturally the City disputes this. And it looks like the whole issue will end up in court.  Meanwhile the plant is not operating at all nor is any water being produced.

Like this as your neighbour?  Possibly the largest desalination plant in the world.

Australia:

There has been massive anger in Australia over desalination plants dotted around the coast.  Protests drawing hundreds of people objecting to the plants sprung up all over the coastline.

If Demand management works so well, and Cape Town has proven that it works so well that demand for water is around one third of what it used to be, why then invest in the high fruit when low hung fruit is readily available?

Nasty nasty Cape Town City Council.

Nasty nasty Cape Town City Council.

Water has made the city nasty.  Since 2017 when day zero was imminent, Cape Town City has turned very nasty over water.  Here are listed some instances of how bad they really have been.

2015:

This was a year in the beautiful and placid Hout bay of the time. Plentiful rain had fallen, the dams were full and the beautiful Fynbos on the mountain ranges surrounding the valley was verdant.  Not so fast.  Poverty had come to the village.  Corrupt politicians and government bureaucrats deprived the local fishing community of their permits to catch fish and turned to illegal means to make a living.  Drugs like TIK (methamphetamine) was cheap until everything that could have been stolen from the addicts own home dried up. Crime was rife and the lure of a brass water meter on the street of each house was temptation turned into a reward of money for scrap.  Water could be seen under huge pressure (water pressure in Hout Bay is 16 Bars in places) early each morning from almost every house in a single street.  Like a river this would run down the road.  So bad it was that the City ran out of water meters.  They simply connected the supply pipes without meters directly to the houses. What happened from here on was the nasty bit.  When realization hit the city and eventually it did sink into their dumb heads that in order to make the little water in the dams go further people would need to use far less water.  In came restriction levels one after another.  2, 2A, 3,3A, 3B, 4, and 5.  All of this happened in a matter of 7 months.  Cape Town citizens responded.  Some did not want to and they got punished.  However the response overwhelmingly was compliancy.  Nobody watered their gardens with municipal water any more, gathered up grey water for flushing toilets, and used whatever was left over to pour into thirsty pot plants. Radio stations called for tips from their listeners and the talk of the town was Water… Water Rhapsody installed more systems to conserve water than ever before.  These were mostly Rainwater harvesting methods for household use as many of our clients already had our grey water systems to irrigate gardens.  Besides which the precious greywater was mostly used for flushing by means of buckets.  Pools were filled from rainwater tanks and pool backwash systems were in huge demand.

The city took more than two years to replace these stolen water meters and carried on charging the same volume of consumption as the prior to the new restrictions despite that the poor and naïve consumers of water without water meters without any means of proving their low usage carried on paying for water with bills of over R2000 per month despite their careful use of the precious resource.  The city during the crisis months allowed 300 litres of water per day far less than they were charging for the estimated readings from previous years. I personally saw the readings (before and after) new meters were installed.  The new amounts despite the massive rise in water rates amounted to not more than R36.00 per month.  The city in a display of unique unfairness refused to countenance any pay back of what should have been in excess of R47 000.00.

Clients of Water Rhapsody using our Grand Opus Rainwater Harvesting Systems which supply rainwater from roofs to feed into water tanks, pump, and filter this water to whole households in an attempt to live normally and get-off-the-grid during the rainy season.  Any harvested rain as well that falls in any of the months outside the rainy season is a bonus to them and should have been a bonus to the Cape Town City Council as well as all of these systems must have been a relief to their stressed water supply.  Not a bit of it… they were grievously peeved if anyone should have no reading whatsoever on their water meters for three months.  They automatically despatched an inspector who would open a tap somewhere on the premises and if the water meter did not operate this was enough for them to erroneously conclude that the water meter no longer worked.  They were conscientiously blind to the fact that a demonstration of our system showed that the water in any tap was harvested, tanked and pumped rainwater.  They simply went to report that the meter was faulty, and despite no water for the forthcoming months was demanded from the council were given the same short shrift treatment as those poor folk in Hout bay.  Imagine their frustration at being told to pay huge estimated bills having spent a small fortune precisely to avoid this.  Water Rhapsody Clients simply had to pay these bills without any recourse to and safety from the law as if they did not pay were threatened that their water would be cut off and would need to pay a re-connection fee.

Water meter readings

Brass water meter-out with the old.  Want to read the meter?  Read only the white numbers as these are the kilolitres.

It gets worse can you believe?  At some later date, the city workers would duly arrive to change the water meter.  This was one of the new high tech models, designed more than just measure the volume of water.  This device measures the water on a daily basis and is also an automatic cut off device set to close off the water once a daily allowance set by the city is reached.  These though too can fail.  Some of our clients refused to allow this new meter to persuade them to use municipal water and so the city would come every three months to put in yet another “broken” water meter.

Best advice I give to my clients is: use at least one unit (kilolitre) of water from the council every month and pay the R18 for that to avoid the compounding stupidity of those who adhere to the adage of “none so deaf as those who will not hear”

I have been doing what I do to get people to use less water and become mostly self-sufficient from the council supply.  Each time there is a perception of a drought perceived or real, the volume of work goes up exponentially.  This is really stressful when I am simply unable to get to help everyone in time.  To add insult to injury, the Cape Town City in an effort to get everyone to use less water have a raft of ways to just that.  These include water restrictions and water tariffs.  In a meeting with the City in the period of the impending “Day Zero”, we were told by the city that we must “gear up”.  Fine was my response, but questioned what would happen to restrictions once rains started to fall.  I recall well that the answer was that they would never go below restrictions 3B.  I accuse them of lying about that and have witnesses aplenty to vouch for that.  By the end of March 2019 restrictions were already lowered below that mark.  Good men have lost their jobs thanks to the brazen lies from the council officials.

In with the new –  Water meter depicted with automatic shut off device giving the city the ability to shut off water if a daily allocation has been reached.  This new water meter will pass on any unused water to the next day but will not pass on any carry over at the end of the month. The unused water is lost to the consumer.

Cape Town’s Aquifers

Cape Town’s Aquifers

We have three substantial aquifers.  These are the aquifer under Table Mountain, the Cape Flats and what is known as the TMG (Table Mountain Group) Aquifer, which is not the same as the first.  We know that the Cape Flats Aquifer gets recharge every year, but as for the other two, very little is known.

The late Bryan Davies who was one of the beautiful people who were instrumental in the tart up of the FWRU (Fresh Water Research Unit) at UCT and who was highly vocal about his objections to any abstraction from the TMG Aquifer.  His logic was simple:  we do not know when or how long the recharge of the aquifer will be, and where if any recharge is to come from.  If this is to come from rivers, this will then deplete the rivers and any abstraction from our dams for use in the city and farming will be reduced.  Take that!  He believed that the source of the fossil water in the aquifer came from the last ice age.

The quality problems relating to the extracted water from the TMG aquifer are mostly some iron and manganese which both of which leave a bitter metallic taste to the water.  This may easily be removed by oxidising by aerating the water which will most likely happen anyhow as the water may be allowed to flow over some rocky or sandy areas before arriving in a river which leads to a dam, and then water from the dam is chlorinated and flocculated and sent into the pipelines for use in the City of Cape Town.

Cape Flats Aquifer:

 

 

 

 

 

Contractors drilling for water in the Cape Flats

E-Coli: The Cape Flats aquifer has many and different problems.  Many of the older previously outlying areas from the city centre (now sprawling suburbs) had sceptic tanks which allowed the digested human faecal matter to run into soak away trenches otherwise known as “French Drains” for decades.  This provided a natural feed of recharge for the aquifer but with very poor quality water naturally loaded with E-Coli.  Those coliforms are still there, and are waiting for new hosts.  Drink this raw water and expect tummy problems of a very serious nature.  This water may very well kill one especially a baby.

Cape Town sewers are thousands of kilometres underground through the Cape Flats.  No wonder then that there have been regular spills of the raw stuff into the aquifer.  The water in the aquifer moves around one meter per day so in a matter of a few years has moved several kilometres carrying its contaminated company.

Add to all of this old pit latrines, and it would be fair to say that the Cape Flats Aquifer is polluted!

Salinity:  one must never forget that the sea once covered the Cape Flats area.  Parts of the Cape Flats are super high in salty water and the deeper one drills for water in this aquifer the worse is the salinity.

Iron: it is quite astounding how the quality of groundwater differs from place to place and water in a well point or borehole only a few metres apart may have such differing iron content in the water.  Iron rich water may be crystal clear when extracted but allowed to oxidise the iron turns brown and stains everything.

Clay:  some boreholes extract water loaded with fine clay.  The clay forms a colloid and does not easily settle.  Used for irrigation the cleaves of plants get covered with a creamy coloured liquid and dries to a powder when dry.  This water is useless to anyone who has this quality water.

All mixed together:  High salinity often goes hand in hand with iron. This mix is toxic to plants and will kill them.  Any thought of using any of the water with a combination of problems in homes will find the mix very difficult to overcome.

Despite these problems, Cape Town City are drilling boreholes all over the Cape Flats with the intention of using this water and blending it into the water supply of Cape Town.

Lastly the quality of ground water not only differs from place to place, but also remarkably from one season to the next.  The quality is typically worst just before the winter rains when the water table is lowest.

Table Mountain:

The biggest problem of the Aquifer under Table Mountain is the low pH of the water.  This acid water dissolves copper pipes and extended use these start bursting.  The water is difficult to balance and indeed resists balancing with normal practise, and most often needs dosing with strong caustic before the pH can reach acceptable and safe standards.  It must be borne in mind that that copper is a heavy metal and if water with a low pH is used, the copper dissolved in the water may reach toxic levels causing copper poisoning.

Falling Water Tables:

The aquifer at Table Mountain as now porous.  There are now thousands of people extracting water from this mountain the water table is in serious trouble all over the place.  Sea Point:  sea ingress.  Southern Suburbs:  table falling to levels where places no longer get any water at all.  Hout Bay:  water quality shows serious stress.  Constantia:  pH levels are falling needing constant upgrades to methods of balancing the pH.

Does it then make any sense to drill for water and extract this falling resource and ignore and yet throw away the rainwater that falls on one’s roof?  Rainwater is far safer easier and cheaper to harvest that ground water.  The only problem it falls when one thinks one cannot use the wonderful stuff that falls from the sky.  This should not be seen as a problem as rainwater may be used as a supply to the whole household and thus for at least half of the year.  If the Cape Town City Council would only come to the aid of users of winter rainfall for household use,  to get some consideration for their rates for summer / dry season.  The city should in fact look at the entire years supply and divide the years supply into 12 months to get an average use and charge for water at that rate even if this is a slightly higher rate than on the normal monthly basis.  This of course will never happen because the city makes pots of money from the cash cow called water supply. The more water sold the better until we should run out of water which could well happen, and this time – really run out.

The City needs to be very cautious drilling and extracting water from our aquifers.  Constant monitoring the tables and the quality of the water will keep those in charge of this on their feet.

Jeremy Westgarth-Taylor