Cape Water and Dams Report
(Bullshoek Dam. Now 100% full. Photo : DWS)
Dams – Latest levels: Winelands and Cape Town
Report nr. 122 (updated 8th October 2018) on the main dams serving
Cape Town City and nearby Boland/Overberg towns
Inflows to the dam catchments tapered off last week, giving a small net inflow of 2.1 M.cuM (0.2% of capacity). Total water in storage rose slightly from 75.5% to 75.7% of capacity.
Last year, the same week saw levels drop by 2.0 M.cuM (0.2%) to 37.2% of capacity.
Here is our chart of weekly net changes in the combined amount of water stored in the 6 main dams (click the chart to see a larger image).
September produced more good inflows from which all the dams benefited. However, during this past week the level of several dams fell as the net outflow patterns of summer commenced. Interestingly, the Steenbras dams fell the most; a draw-down that makes good sense given that they may benefit from the rain forecast for next week. The overall water stored may be expected to peak by 3rd or 4th week of October as the winter rainfall period ends.
Looking ahead, I am comfortable that my outlook of water consumption for this coming summer season reasonably comprehends the newly eased restrictions. We can now wait until early November before making any adjustments – that is when DWS will decide the new water allocations to be applied for the 2018/2019 hydrological year.
(Here is our model projecting the amount of water likely to be stored in the dams each month)
Putting it into context!
It seems that the SW Cape dams will end winter at a collective level around 75% of capacity, which equates to some 675 M.cuM of water. Based on past averages it seemed that the best we could have hoped for was to reach 65%, but this winter nature delivered the water accurately into the catchment areas and so we have enjoyed the best recharge of the dam levels in the past 10 years.
In fact, the net recharge could end up at around 490 M.cuM, almost 55% of capacity in one winter season. True, the reduced rate of water usage will have helped but usage tends to anyway tumble in winter, especially when good rains fall.
Nonetheless, despite this being a very gratifying result and great relief to all, it is understandable that after the fairly traumatic past few years – particularly the very worrying February/March period when “Day Zero” threatened – it is natural for many to favour continued restrictions and to feel anxious as soon as the dam levels start to fall.
I recommend that we all relax somewhat and start to enjoy the good water supply that we now have. It is a peculiarity of the system that the authorities now need to switch emphasis from saving to consumption, and to encourage usage to rise again. Why? Water must be sold to cover the high cost of maintaining and expanding the water distribution system as well as financing the augmentation initiatives. Importantly for us all, as water supply/distribution costs are relatively fixed, the more water that is sold the lower the tariffs (price per kilolitre) can be thereby reducing everyone’s cost of water, no matter what one’s personal level of consumption/saving may actually be.
We, the consumers, need to remember this recent painful lesson and to ensure that each of us is more careful with water in future. We have shown that we can get by using surprisingly little water and should therefore incorporate these methods in our future daily lives by adopting water-wise living practices and grey water re-use. Doing so could see us all getting by with, say, 150 L/person/day instead of the 250 L/p/d that we were accustomed to consuming before. If we did only this it would save us the equivalent of a full Voelvlei dam of water every year. Vitally, such permanently reduced demand would mean that the more typical annual winter recharge of 250-300 M.cuM into the dams would be sufficient to hold our water reserves at acceptably safe levels.
For their part, the authorities seem to have learned much about effective management of the system and of how best to reduce wastage and failures. Importantly, the absolute need for various supplementary means to produce extra water seems to have now been wholly accepted, and it may be expected that various large scale augmentation steps will be implemented over the coming 2-5 years. Additionally, the water and sanitation departments will need to be more watchful and to react sooner to indications of approaching lower rainfall patterns.
A vital effort is being made by climatologists to better understand what actually happened to cause this water shortage and how to better recognize the onset of such conditions in future. To the extent that it is possible to do so, this should result in improved mitigation strategies that may be implemented earlier, both to stave off potential disaster and also to better manage and ameliorate the impact of inevitable restrictions on the various users, particularly the agricultural irrigation sector.
The augmented water supply this past week was 45 ML/day. Consumption from “all sources” was 546 ML/day while water drawn from the main dams stood at 501 ML/d. The trend lines have been good since early-2018, but obviously relaxation of restrictions will now cause a trend reversal.
(Graph tracking overall use and production of extra water through the augmentation efforts)
Read full report on status of Cape Town’s augmentation efforts here.
How well are we actually doing overall?
The CoCT graph of the combined dam levels demonstrates the situation very well. We must now be at or very near the peak level that will be achieved this winter.
Inland, the Brandvlei Dam stands at 61% and Kwaggaskloof Dam is at 59% of capacity (being irrigation farmers dependent upon these Breede dams ourselves, we have already been advised that we should receive our full allocation of irrigation water this season). Inexplicably, DWS did not at least issue guidance to the BRD and TWK irrigation users in SW Cape as to what their situation would be. Clanwilliam Dam remains full at 100% with Bullshoek Dam also back to 100%.
One area that remains very stressed is the Klein Karoo, where the drought is tougher than ever and entering its 4th year. Four of their dams are empty, six are less than 7% and three are only 15% full.
Will the weather help?
Here is our chart showing cumulative rainfall for the month-to-date as was recorded at the dams.
Click here to see ShowMe Winelands Weather forecast of possible near-term rain.
What rain ought we to now expect?
Rain is predicted for 13th-15th October, although likely concentrated along the Overberg, south coast and adjacent land areas. The Antarctic oscillation is forecast to be negative at that time meaning that the south Atlantic high pressure zone could retreat equator-wards, allowing space for a low to develop and bring in 15-25 mm of rain. This should particularly benefit the two Steenbras dams.
Apart from occasional scattered light rain, not much else is to be seen in the forecasts except for a system that may arrive during 1st week November, bringing 15-20 mm of general rain on the 4th/5th.
ENSO, which has remained neutral since April is now kicking in with sea surface temperatures rising above +0.5degC. The forecast is now 70% that a mild El Nino will prevail through our summer.
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What are the authorities doing?
As promised, the Metro and some other SW Cape municipalities eased restrictions to level-5 from 1st October. Individual water allowances rose from 50 L/p/d to 70 L/p/d and the tariffs declined, with the basic tariff in Cape Town reduced from R28.90 to R21.19 per Kilolitre. Rules for use of water are unchanged. Further gradual easing is expected once DWS revises allocations at end-October.
The Metro W&S department hopes that many users will continue to save water and therefore benefit from the reduced tariff. Those who do elect to make use of the increased allocation should be aware that if that increased use takes you up over 6 KL per month on to the second tariff step, although this step-2 tariff is also reduced, it nevertheless still costs more than step-1 does. Therefore not only will you pay more for the extra volume of water used, but all that used above 6 KL/month will be priced at R34.43/KL (reduced from R46.00/KL). This is still higher than the previous tariff of R28.90 that applied to your consumption when on the first step.
Read the City of Cape Town press releases here for background and details of reduced tariffs.
DWS announced that work has started on raising the wall of Clanwillam Dam by 13 metres. This will reportedly roughly double its capacity (presently 122 M.cuM) and will allow for up to an additional 5000 ha of irrigation farming in that area. Preference will be given to new equal-opportunity growers. This investment will have no direct bearing on water supply to the SW Cape municipalities.
Unfortunately it is understood that due to a shortage of money, DWS will not commence the planned Berg River – Voelvlei diversion which was expected to augment effective storage for SW Cape by up to 20 M.cuM. It is not known when this project will now begin.
It has been announced that Department of Environmental Affairs has allocated R1 billion in financial support to Western Cape to be used for drought relief, feed stock for animal herds, restoration after fire damage and funding of water production augmentation projects.
Now that we have saved ourselves from immediate disaster, what next?
It has been stated that our goal has to be ‘resilience’ that will lie in the diversification of water sources making SW Cape municipalities less dependent upon rainfall for its future fresh water supplies.
Why ‘resilience’? Well the expectation clearly is that unpredictability of weather is likely to increase as climate change progresses; our systems will need to be flexible and resilient enough to deal with the probable challenges arising therefrom.
We have just collectively experienced how relentless the weather can be, and how powerless we are to influence it over the short-term. We could only react to circumstances with which we were confronted and hope that nature would relent before disaster struck. And in the end it did relent and the rains came, but it was when we were just 2 months before plummeting into an apocalyptic abyss. It would be extremely irresponsible for us to allow ourselves to end up in a similar situation again.
Debate on what to do next is likely to blast on unabated, with views and opinions flowing freely about the possible causes and many forms of potential mitigation being considered. In the process there are two key underlying threads that will need to be borne in mind throughout:
1) Demand, influenced by local population expansion, water usage practices, changing lifestyle expectations and location/delivery limitations.
2) Supply, confined to primarily surface water captured in and supplied from our main dams, supplemented in time by other variable sources of fresh water and means by which extra potable water can be produced and delivered.
Getting the outcome right will, of course, be of great importance because without a dependable supply of fresh water in the volumes required at bearable cost levels, growth will be stifled and economic activity in the area will stagnate.
This challenge confronts the entire nation, but the Western Cape is unique in that its climate is diametrically different to that of the rest of the country and its unique situation and setting offer potential solutions not available to all other parts of the country. Therefore it is essential that we seek to develop appropriate local solutions and fight for the right to implement them in the measure that we believe is appropriate and to the extent that we are willing and able to afford. We have the necessary skills and resources available but can we secure the right and marshal the support needed to succeed with our efforts?
In pursuit of our agreed objectives there will be two key institutional wild cards with which we will need to contend. Without their cooperation, success will be very elusive.
1) DWS; has the right and ability to assist or hinder us to access and deploy most of our available water resources. DWS’ actions are likely to be guided politically and limited financially.
2) Eskom; access to a reliable and competitively priced supply of energy will become pivotal as soon as we pursue supplementary sources of water where the energy is not provided by nature. Without their support we may not be able to save ourselves, but perhaps they may start supportively only to later unpredictably and uncontrollably fail along the way for other unrelated reasons, thereby bringing any commenced initiatives to a grinding halt.
Also, It is suggested that we need to philosophically treat water as a (unlimited) flux (= a flow) and not as a stock. I prefer to think of it as both.
Relatively simple to capture, surface water is straightforward to store and access when needed. The greatest challenge is that nature tends to deliver it in large clumps that sometimes make it awkward to handle, channel and get to storage; and additionally not well synchronised with demand. But nature does the “heavy lifting” and so costs are minimised. On the other hand, produced water can be ‘made’ and supplied smoothly as needed and doesn’t need significant storage facilities. However, the ‘production’ of fresh water is far more complicated and costly, especially in large volumes.
So while ‘produced water’ may be more dependable in supply, its higher cost makes it unlikely that we will ever depend solely upon such water sources.
In the end the water supply equation is likely to comprise many components, each contributing its own benefits and costs, hopefully resulting in a suitably balanced and cost-efficient outcome.
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Summary: Combined levels of the six main reservoirs serving the Cape Town/Overberg/Boland area rose from 75.5% to 75.7% of capacity. More rain is expected mid next week.
Read about Cape Town’s Augmentation fresh water production program here.
Read our Indoors Water Savings Ideas here.
Read our Outdoors Water Savings Ideas here
Read about a D-i-Y household rainwater harvesting and tank system here
Tom Brown.
Retired international businessman with a background in Finance and IT; and now a fruit farmer, with a passion for the weather and climate.
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