Cape Water and Dams Report
(Poortjieskloof Dam. Now 65% full. Photo : DWS)
Dams – Latest levels: Winelands and Cape Town
Report nr. 117 (updated 13th August 2018) on the main dams serving
Cape Town City and nearby Boland/Overberg towns
A better week. Weekend rains in the catchments saw total combined levels to rise by 16.2 M.cuM (1.7% of capacity). Overall water in storage climbed from 56.7% of capacity to 58.4%.
In the same week of 2017 the dam levels lifted by a similar 15.3 M.cuM (1.6%) to 30.7% of capacity, over 30% for the first time last winter.
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With the restatement of the dam level forecast model (see below) I have assumed that level-6B restrictions will remain in place until end-October 2018 and then be relaxed back to level-5 (87 L/p/d) and that 20 M.cuM per month will be released for agricultural irrigation purposes across the summer season (Oct-Mar) plus 10 M.cuM pm on the ‘shoulder months’ (Sep and Apr). Lastly I have assumed a slightly below-average annual rainfall pattern but with a historically normal distribution pattern across the months.
This indicates that we would end October with around 556 M.cuM of water in storage (62% of capacity). That would meet our goal of exiting winter with water stored at more than 60% of capacity.
Of course this could change quickly if more good rains arrive. But until that happens we should not assume that the drought is finished with us yet.
(Here is our model predicting the amount of water likely to be stored in the dams each month)
Putting it into context!
A very significant milestone was reached this past week: extra water produced by the various augmentation initiatives reached 50 ML/day for the very first time. Well done Cape Town Water & Sanitation Department for attaining this important goal.
The simplest way to visualise this is that one glass out of every ten glasses of water that you drink now comes from the augmentation effort while the other nine glasses of water still come from the dams.
Seen another way, 50 ML/day across a population of, say, 4 million people amounts to 12+ litres of water per person per day. So should all our dams run completely dry, a most unlikely scenario, then at least there could be enough water produced to ensure that we could all survive.
Looked at on an annualised basis, 50 ML/d translates to 18 M.cuM of water; more than one month’s supply for water for all the SW Cape municipalities at current water consumption levels.
Of course we must also keep this in perspective – rainfall for the first two weeks of August delivered to the dams the same amount of water as all our augmentation efforts would produce in a year. For some years to come, we’ll remain reliant upon rainfall as our principal source of fresh water.
What progress is Cape Town making towards augmented ‘resilience’?
Progress appears to be steady. Groundwater sourced from the aquifers should see the total contribution of extra water gradually climb, week by week, to 60 ML/day.
Augmentation will take it’s next significant step up when the pilot recycling plant at Zandvliet comes into production; expected to add about 10 ML/day to the total supply at that time.
The goal remains for extra water production to reach 75-80 ML/day by December 2018. At that stage one and a half glasses out of every ten glasses of water will be coming from augmentation.
This graph shows how the production of extra water has grown steadily since early 2018 and the trend lines evidence that although overall consumption remains static in the 500-520 ML/d range, the extra water produced is resulting in a direct reduction in the demand for water from the dams.
(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?
As may be expected, the CoCT graph of the combined level of the 6 main dams shows a useful improvement last week. Our expectation is that the spells of rain forecast for the rest of August will boost us above the 60% level.
The two large inland Western Cape irrigation dams, Brandvlei and Kwaggaskloof have now both passed 40% of capacity, promising eased water supply conditions for inland irrigation farmers. Clanwilliam Dam is full and spilling.
Will the weather help?
One general problem at the moment seems to be that while the South Atlantic High has moved away somewhat allowing the cold fronts to approach the land, the systems that have arrived so far in July and August have tended to be weak/shallow, lacking penetrating strength. Additionally, because they are skirting south around the High, the approach angle was more from the south and south-west (instead of the preferred approach from the north and north-west). As a result these weak systems have tended to be deflected away by a stable high pressure zone over the land and dropped their rain south of the mountains and over the sea instead of pushing through to the larger dams behind the mountains.
Our chart of rainfall at the dams shows August month-to-date as being well behind the averages. There is a small hope that the prevailing flows will deepen and strengthen toward end-August and that more energetic, thundery weather will bring late rains.
Click here to see ShowMe Winelands Weather forecast of possible near-term rain.
What rain ought we to now expect?
1) All the main dams benefited from rains last weekend. More general rain is forecast to fall over 16th-17th August. The on-coming system is not deep and it is not carrying much water, so the expectation is for 20-40 mm in the Dwarsberg area and only 10-20 mm of more widespread rain.
2) 30-40 mm of rain is expected in the mountain catchments between 22nd and 23rd August.
3) 15-20 mm is predicted to fall generally across end-August.
4) At longer range, two good spells are predicted for September; 60-80 mm across 5th-8th and 30-40 mm across 28th-30th.
ENSO is holding on/about the neutral level with a slow upward tendency. Other NOAA charts show the ocean warming is building in the west Pacific and indicate El Nino will probably start to take hold in September.
What are the authorities doing?
There is not much to report here this week. The focus remains on rolling out pressure management systems and implementation of augmentation efforts. In nautical terms: ‘steady as she goes’.
What is the citizenry up to?
As many will have read, a fresh initiative has started under the leadership of Dr. Anthony Turton in conjunction with the Facebook group, Water Shortage South Africa. They have announced several actions to focus on and try to turn around the increasingly calamitous pollution problem that is developing in the Vaal River and other inland river systems. These include:
1) seeking Constitutional Court clarification of aspects of chapter 3 of the constitution, in particular seeking to enable DWS and COGTA to impose stricter performance standards on the many municipalities whose water treatment and sanitation activities seem to be failing precipitously.
2) breaking through the curtain of “impunity” behind which so many state employees appear to operate hopelessly ineffectively and yet apparently without any sense of accountability or fear of consequences for failure.
This initiative is asking for moral and financial support from interested citizens.
Read more about this “Water Lions” initiative at https://www.watershortagesa.com/
Watch Dr. Turton being interviewed on SABC Focus and read about the problem in more detail at https://www.thesouthafrican.com/dr-anthony-turton-vaal-river-fix-r800bn-r1tn/
If you wish to contribute to this cause, visit https://www.watershortagesa.com/donatewaterlion
How might the developing inland water crisis effect us here in the Cape?
While we can be very grateful that our elected representatives and appointed water and sanitation management officers in the Western Cape and its municipalities have not permitted a similar dereliction of duty to arise in this province, we need to keep a close eye on the up-country situation. If the water and sanitation services in those areas continue to fail at the current tempo then we have a number of possibilities to fear.
– spread of disease and illness,
– accelerating decline in economic well-being and increase in unemployment,
– security failures and societal disruption,
– ‘refugees’ fleeing what could become intolerable circumstances and threat to life.
If this came to pass it would effectively mean that those municipalities had negligently and utterly unnecessarily directly caused a “Day Zero” condition to happen to them.
These and other factors could see people from other parts of the country stream towards the Cape, seeking safer living conditions, employment and simple refuge. With the next election due in 2019, such an issue could become a bitter fight, with populists seeking, fairly or unfairly, to turn circumstances to their advantage.
If on top of this an overall water shortage returns to the interior – as the possible near-term return of El Nino seems to be signalling may happen – then an inland drought could morph into a wider crisis. Combine this with threatened land expropriation, concomitant land invasions and persistent lack of effectiveness of our security services, and the situation could become rather ominous.
I don’t wish to be a ‘prophet of doom’ but one only has to read up about what has happened under somewhat similar circumstances in Venezuela that have turned that once prosperous country into an absolute ‘basket case’. We have to guard that something similar does not happen here.
Summary: Combined levels of the six main reservoirs serving the Cape Town/Overberg/Boland area rose from 56.7% to 58.4% of capacity. Some useful rain is expected toward end-August.
Watch me answer the often asked question: “why do you write this report?“
Read the full City Cape Town release about Water By-law amendments here.
Read here about Cape Town’s reduced water and sanitation tariff increases.
Plan ahead for possible water outages; here are points that could help you.
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
Report instances of piping failures and incorrect use to municipalities.
In Cape Town the contact details of the 24-hour Technical Operation Centre are: Email: waterTOC@capetown.gov.za Telephone: 0860103089 (choose option2: water-related faults) or SMS: 31373 (max 160 characters).
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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