Dams – Latest levels: Winelands and Cape Town
Latest report (updated 5th February 2018) on the main dams serving
Cape Town City and nearby Boland/Overberg towns
Continuing the improving trend, net outflows from the main dams declined last week to 7.2 M.cuM, or 0.8% of total dam capacity; vs the preceding week’s far higher 8.5 M.cuM. Combined dam levels dropped during last week from 26.0% of capacity to 25.2%.
During the same week in 2017, the main dams dropped by a far larger 14.2 M.cuM, falling 1.7% to 36.9% of full capacity.
For the first time, the water consumed last week was less than half of the (14.6 M.cuM) water consumed during the same week in 2017. This can be seen clearly in the following graph. Note also that I am showing estimated evaporation for the first time. At this time of year and at current consumption rates, roughly 1 week out of 5 every weeks of net outflow is actually lost to evaporation.
Current status?
Combined water stored in the 6 main dams fell to 223.9 M.cuM (139 M.cuM of easily accessible water) (last year, levels dropped to 328 and 243 M.cuM respectively over the same period).
How long will the remaining fresh water last?
Given that DWS has throttled agriculture’s water use for irrigation at or about the agreed 40% level, overall consumption is falling fast and it is becoming clear that we can survive through to winter if we save water and reduce collective consumption in the Metro below 450ML/day. In recognition of this trend, today the City of Cape Town moved its “Day Zero” date out to 11th May, i.e. by one whole month from where it stood last week.
Essentially we are aiming to reach the end of June with at least 110 M.cuM of water left in the dams. The sums are easy. If we collectively can drive net outflows (including evaporation losses) down to below 7 M.cuM per week then, even with zero rainfall, the water that we now have stored up in the dams together with that being transferred from the Kogelberg dam will last until mid-June, by which time some rains should arrive.
As can be seen from the progressive prediction below, with 224 M.cuM of stored water in storage at 5th February we came in slightly better than the 222 M.cuM predicted. Impressively, in January 2018 we ended up using only 48.6 instead of the 95 McuM used 2 years ago in January 2016.
I have not yet added anything in for the amazingly generous donation of water from the Groenland Water Users Association, concluded just recently. Essentially the Elgin and Grabou farmers have offered some 8 M.cuM of water to the WCWSS which will flow into the system during February and March through the Palmiet canal into the Upper Steenbras dam and on into the Metro water treatment system. This will amount to some two week’s supply for the Metro and allow us to safely reach mid-June, even if no rain falls whatsoever.
What actually is going on?
Now that agriculture has contributed all that it can, why is it that the heaviest remaining burden of reducing water consumption rests with formal households. It may seem harsh, but if we consider the overall water usage by sector in Cape Town it indeed makes sense that households should be called on to make extra water savings.
1) Of the, say, 550 ML/d of water that presently flows from the water treatment works into the system, some 26% comprises so-called ‘non-revenue water’. Around 15-16% is lost due to leaks and system failures. This is a world-class excellent result and by far the best in ZA. The remaining 10% does not generate revenue for a variety of reasons including free services, non-functioning meters, theft and so on. Thus; other than constantly improving break-fix, scheduled maintenance and enforcement to minimise losses, management has to focus on reducing demand across the other approximately 74% of water produced and distributed by the City, i.e. currently 410 ML/day.
2) Water consumption in informal settlements currently stands at around 4% in the metro. As these citizens have already been at Day Zero for years, queuing at stand pipes to collect their average of 40 litres per person per day. There is no justification for increasing this hardship.
3) City and state entities consume around 7.3%. As this is largely unchanged it indicates that these offices, hospitals, clinics, etc have been reducing consumption in line with the targets.
4) Business uses some 17.7%. This has been edging up from the 14.9% where it stood a year back. Clearly business use is ‘stickier’ especially where water use is part of a production process. We need to support continuity of business because that is where so many work and earn an income. However, we must add to our personal use any water that we do flush or consume at the office. So if we consume, say 12 litres/d at the office, that leaves only 38 litres for ‘honest’ use at home that day.
5) Formal households consume about 65% of the water vs some 67% a year ago. It is interesting that business + formal households have stayed at about the same combined percentage of around 82.5%. One implication is that some household consumption may have shifted to the office, factory or school (e.g. taking showers at the gym instead of at home). Nonetheless it is in the households that greater savings can be made without jeopardising our vital economy (more below).
We appear to have now passed the point of maximum water consumption.
DWS reports that most of the allocations to agriculture for all purposes (irrigation, animals and human consumption) are being closed off steadily as the agreed 40% limits are reached. According to user reports, releases into the Berg River have stopped. Vyeboom has been closed for some weeks and the valve releasing water into the Sonderend River has been closed for over a week (it will only be opened intermittently to boost supplies for domestic use). This graph issued by CoCT shows the situation during the last week of January. Further reductions will occur by mid-February.
City of Cape Town today acknowledged the reduced agricultural water use and amended its prediction of “Day Zero” to be 11th May 2018 (point red ‘X’ in the drawdown tracker chart below). Given that we are today at point red ‘Y’ (25.2% of capacity on 5th February) we are progressing perfectly down the edge of zone ‘E’ denoting the extra water made available by agriculture.
What now should happen to the consumption pattern is that as residential savings build up and evaporation eases, point red ‘Y’ should start to follow the dotted white line curving away toward point “I”, around end-June or early-July. This was made more sure by the announcement this week of the donation of 8-10 M.cuM of water by the Groenland Water Users Association which, once it is transferred to Steenbras dam, should on its own achieve half of the target savings denoted by the blue zone ‘H’.
So, as I have proposed before, it now seems reasonable to set ourselves a ‘Success-Target‘ of the dams being at or above 11% of capacity i.e. around 100 M.cuM of water stored, by end-June 2018. At the moment we are 95%+ probable to achieve this outcome; and we should be able to do so even without any rain falling in between. This, in turn, would enable the City to delay implementing the disaster plan stage-2 of collection/rationing at least until end-June, provided households reduce their water consumption over the coming 4-5 months as requested.
Given that some notice (assume three weeks lead-time) is necessary to start the “Day Zero” program rolling, an announcement may not be necessary until early June; if at all.
What are the authorities doing now?
The new metro leadership team has adopted a far more transparent communication strategy and, instead of hinging on fear, is instead encouraging water saving in order to avoid possible disruptions.
The Minister of Water and Sanitation has apparently proposed that an unused desalination plant lying at Umgeni Water in Durban now be transferred to Cape Town and be installed at the V&A site; costs for account of the City. It remains to be seen how this gratuitous intervention may play out.
Oddly, Dept. of Water and Sanitation is actively discouraging potential water donors in Gauteng from sending potable water supplies to Cape Town. Seems they are worrying about running out of water on the Highveld, again??
Enforcement continues. Regrettably scenes of violence and intolerance have started to occur at the Newlands spring site. So those water outlets will now be relocated to the nearby swimming pool area where crowd management and vehicle access will be easier.
Planning of the Points of Distribution continues but no details have been released yet. It is to be expected that, given the reducing water usage and possibility of avoiding “Day Zero” the City will correctly wait until the last possible moment before committing to these expensive installations that would serve no other purpose.
DWS continues to work on the extra pumping facilities at Voelvlei and Theewaterskloof dams. Voelvlei should be operational by end-February and TWK by some time in March.
The City is progressing with its initial two temporary desalination plants which are now about 68% complete and due to commence producng fresh water in March ramping to full production by June.
Drilling into the Cape and TMG aquifers is proceeding. News is that the initial yield from the boreholes on the Cape Flats is better than anticipated.
See details of Cape Town’s planned interventions to produce fresh water here.
Learn about water savings efforts by other Cape municipalities – read more here.
Hear me interviewed on Bok Radio here about the overall water situation in the western Cape
Do visit the City of Cape Town website to see additional graphically presented information regarding the water situation – very helpful.
1) See the full water status presentation here and
2) Check out water usage for your property and of neighbours, friends, using this interactive map.
What ought you to be doing?
1) If you can, enrol on your municipality website and submit water readings electronically.
2) Check your security of outside taps, tanks and pools.
3) As I advised before there seems to be no need for any urgent buying; wait at least until April.
4) Remain up-to-date with suggestions advice and tips from others. I suggest that you join a group like the Water Shedding Western Cape Facebook group. Check the website where Dani Nieckau is posting all the hints and tips, all in one easy to read place. Click this link and have a look.
5) Change to extreme water saving, e.g. from short 2-minute, 20-litre showers to brief wetting down and sponging sessions using perhaps just 1 litre each time – water use can be cut by as much as 25% per day. Also, laundry water collected and used for toilet flushing achieves further significant weekly savings.
6) Take care of Hygiene; importantly wash/clean hands regularly, especially working with grey water.
7) Be ‘water warriors’ at place of work. Cut own consumption and seek ways to help others save.
Will the weather help?
Somewhat unseasonally there is a deep powerful low pressure system on its way, developing out of the antarctic circum-polar circulation. Yesterday it was passing the tip of South America and is forecast to strike the SW Cape on Friday 9th February in the afternoon. At the moment the predictions are for general rains for about 12 -18 hours bringing 15-20 mm to most areas and all the dam catchments, with Steenbras possibly getting 30mm.
Hopefully this rain will also help to replenish the Groenland dams from which the donated water will be flowing to Cape Town.
Here is the rainfall chart for the dam catchments for the period since 1st April 2017.
January 2018 was a lean mean month with virtually no rainfall, anywhere in SW Cape.
In Summary: outflows exceeded inflows by 7.2 M.cuM and combined dam levels fell to 25.2%.
Here are the levels of the six main dams serving the Cape Town/Overberg/Boland area.
Here are some of our updated thoughts of possible implications of “Day Zero”.
Plan ahead for possible water outages; here are points that could help.
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
Read about South Africa’s desalination policies and initiatives.
Click here to see Winelands Weather forecast of possible near-term rain.
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.
Views expressed in this article, and comments in response, are those of the writer and commenters alone and do not necessarily reflect the views and opinions of ShowMe, nor is any warranty hereby given as to suitability for any purpose of a reviewed enterprise or as to the quality of offered advice, products, services or value. Copyright ShowMe Paarl. All rights reserved. Copy only with prior permission.
2 Comments
You must be logged in to post a comment.
commentking
Big Fan of the weekly analysis. Would it be possible to insert a higher quality image for the weekly dam drawdown tracker?
tombrown
Hi Dylan.
At the moment we are working with a diagram butchered several times in PowerPoint. I hope to get a clearer version up within a few weeks.
Regards, Tom.