Dams – Latest levels: Winelands and Cape Town
Latest report (updated 29th January 2018) on the main dams serving
Cape Town City and nearby Boland/Overberg towns
As hoped, net outflows from the main dams declined last week to 8.5 M.cuM, or just under 1.0% of total dam capacity; vs the preceding week’s far higher 12.7 M.cuM. Combined dam levels dropped during last week from 26.9% of capacity to 26.0%.
During the same week in 2017, the main dams dropped by a far larger 11.3 M.cuM, falling 1.3% to 38.6% of full capacity.
It seems that my assessment last week was correct, in that having spiked, water consumption then fell back into a more normal range as everyone settled down to being back at work or school and businesses restarted. Of course, visitor numbers also started to decline last week.
Most encouragingly, water consumption this last week was only 75% of the 11.3 M.cuM of water consumed same time in the previous year; so the pattern of our using far less water in 2017/18 than was used in 2016/2017 continues.
Current status?
Combined water stored in the 6 main dams fell to 231.1 M.cuM (146 M.cuM of easily accessible water) (last year, levels dropped to 344 and 259 M.cuM respectively over the same period).
How long will the remaining fresh water last?
Continuing to save water and to reduce consumption clearly remains of paramount importance.
According to my caculations, the average water consumption in Cape Town has recently been just under 100L/person/day. If we can successfully now halve that to 50L/p/d then it is increasingly likely that the remaining water supplies can be stretched out to late June by which time the annual winter rains should have started (dams started to recharge during 1st week June in 2017) and the production of fresh water by the different augmentation initiatives will also have commenced.
If savings at this rate are achieved, it would probably mean avoiding the imposition of the “Day Zero” rationing/collection system altogether; a very worthwhile goal given the huge disruption and potential for unrest and job losses that could arise under Day Zero conditions.
A sign of how the supplementary water production is building up was visible last week in that the Metro used 556 ML of water from the main dams vs 580 ML consumed from ‘all sources’. This clearly signals gradual growth in augmented water production – the recent 18ML/day has increased to 24 ML/day. So, over 4% of all the water currently consumed in Cape Town is no longer coming from the dams. This figure is expected to steadily increase, first when the three small desalination plants come on line and then more quickly as the water extracted from the aquifers starts to flow into the system.
Here is the table showing my prediction of overall water consumption from the 6 main dams over the months ahead. I have readjusted my prediction for January back up slightly and it now seems that we will end January with some 225 – 230 M.cum of water in the dams with only some 50 M.cuM of dam water having been consumed this month vs the massive 81 M.cuM of water used in January 2017. Therefore, even if we receive virtually no rainfall in the dam catchments over the coming autumn months, it will be at the earliest some time in June before we would get to the point where the authorities would have to implement stage-2 of the Disaster Plan; i.e. “Day Zero”.
What actually is going on?
We appear to have now passed the point of maximum water consumption. The following three charts produced by Cape Town City tell an interesting story.
1) Agricultural irrigation allocations are rapidly closing as gazetted limits are reached. DWS estimates that between 75% and 80% of the irrigation schemes supplied by Volevlei, Theewaterskloof and Berg River dams will have closed by end-January. Most of the rest will close during first two weeks of February with only some residual allocation still due to the later apple and pear farmers. It is assumed that any irrigation allocations to farming areas within the metro boundary from the metro-owned Steenbras and Wemmershoek dams will similarly be shut down.
These two graphs show the effect. The upper graph is for the week ended 15th January whereas the lower graph is for last week ended 14 days later. In that short time agriculture irrigation closed down by 17%. It may be expected that further sharp reductions will occur over the coming two weeks. Conspiracy theorists have been taunting the agricultural industry and suggesting that such reductions would not occur. Well here is the proof. The farming communities are under enormous pressure and deserve our gratitude and respect.
On this third chart taken off CoCT’s “water dashboard” it may be seen how agricultural use of water is slowing as it approaches the cut-off line. Some small overshoot is expected but the dotted line showing actual water use should soon ‘flat-line’ at or near the horizontal “Usage Target” line.
2) Personal water consumption continues to fall and my calculation is that average use is already below 95L/p/d, including an average allowance of some 10L/p/d probably being consumed at the workplace and at school. Now the challenge is to get down to 50L/p/d. This is absolutely not easy but is very do-able. It is noteworthy that as one cuts back there tend to be ‘step-function’ decreases in water use; e.g. if one changes from short 2-minute, 20-litre showers to brief wetting down and sponging sessions using perhaps just 1 litre each time, then water use can be cut by as much as 25% per day. Similarly, when laundry water is captured and used for toilet flushing further significant once-off savings occur.
3) It seems that businesses are not saving as well as the residential sector, and could perhaps do more to reduce consumption. Of course this is more difficult if they are to maintain steady production. However, over the past two years water consumed by business and industry, while certainly dropping in overall terms, has risen from 14.9% of the total water used to 17.7%; whereas over the same period residential use, formal and informal, has dropped from 71.3% to 68.9% (government and other miscellaneous uses have remained at around the same proportion of 14%).
4) I remind you of my chart from last week in which I set out to show how the different effects are likely to combine to stretch out supplies and to delay the arrival of “Day Zero”. The problem of simple statistical expressions could be seen in the fact that the nominal date for “Day Zero” has over the past week gone from 22nd April to 12th April and now, by my calculations, should be back around 24th or 25th April. Why is this so volatile? Well the CoCT team simply take whatever the water consumption rate was during the past week and extend that into the future on a straight line that assumes that specific weekly consumption rate will then run on unchanged week after week until the available water is consumed. Clearly this is not accurate, particularly while the agricultural use is changing so quickly. Following the CoCT system, the effect will be that each week as the usage declines, the straight line extension of that usage will move to the right and the date of “Day Zero” should usually shift outwards.
I prefer to properly comprehend the gradually changing water consumption patterns in my model and therefore my predictions of steadily falling weekly water consumption results in the boundary of the diagonally blue-lined area curving away to the right and indicating a “Day Zero” date falling between point ‘G’ in June and point ‘I’ in July, depending upon how well households can further reduce their water consumption over the coming 4-5 months.
I am often asked ‘what future water provisioning strategy should we be considering?’
My feeling is that we need to exploit all the natural strengths and opportunities offered by the SW Cape location and water-related features. This means adopting a balanced mix of water provisioning systems:
– maximise existing dams (raise walls where appropriate, complete the Voelvlei augmentation plan)
– implement rainfall capture systems at all household/business levels; provide cashflow support
– recycle waste water, with secondary distribution and suburb collection points (use spare garages)
– exploit aquifers on managed recharge basis using storm water entrainment
– establish desalination core capacity to ensure survival when all else fails; designed to run 24/7 for maximum economy, location and site designed scalable for a 7x expansion if needed.
What are the authorities doing now?
It appears that a new metro leadership team has been formed of Ian Nielsen, Deputy Mayor, and Alderman JP Smith, who together are driving the City of Cape Town water program.
Minister Nomvula Mokonyane of Water and Sanitation and members of her team have been spending time in the Cape interacting with various groups to support the City in resolving this huge challenge. They have brought with them a team of 25 specialist enforcement officers, the “Blue Scorpions” who are working through certain agricultural areas making sure of complete compliance with gazetted regulations and preventing over-abstraction of water from rivers in excess of agreed limits. Contravening farmers have been served with fines. Sadly, other than increased policing, the minister has not added any new idea or fresh initiative beyond that which was already being pursued by the CoCT/DWS team
City of Cape Town enforcement teams comprising metro officers, specialists of DWS and police have descended upon 14 suburbs from Fishhoek to Khayalitscha, inspected 77 operations and issued fines to 57 operators, mainly illegal car washes using municipal water. A rolling water use enforcement program is planned.
Cape Town has opened its Disaster Centre which will be responsible for coordinated management of the planned 200 PODs (Points of Distribution) around the metro. JP Smith advises that some of these will be large with up to 600 tap points. Some locations will also permit drive-throughs. Generally they are being sized to handle the highest envisaged volume of people in half the total available time. Support personnel and security forces will be on hand to assist, speed up collection and maintain security. It has been confirmed that the system will operate on an honour basis, that IDs will not be necessary and there will be no cash charge for the water. All persons will be entitled to collect up to 100 litres per day in combination for themselves and three others at 25L/day each.
186 POD locations are decided and the remaining 14 locations will be decided this week. Thereafter the city will publish details of the locations and maps of the sites. Special support arrangements will be made to assist the old and infirm.
DWS advises that the installation of extra pumping facilities to abstract water from the deep end of Voelvlei dam toward Misverstand Weir for Swartland users is nearing completion. The equipment is on hand and tested and will be installed as soon as the concrete work is finished. This is expected to be in production within a week. As soon as this work is complete the team will move to Theewaterskloof dam to build a similar construction enabling more water from the deep end to be abstracted toward the Berg River side of the mountains. Costs of these works are being borne by the Department. DWS indicate that with these new measures, both these large dams can be drawn down to around 6% of capacity, thereby freeing up many week’s supply of fresh water.
DWS has issued new instructions whereby people with boreholes and private water extraction points will have to measure water use from 1 February, and restrict non essential use such as gardening to 1 hour every Tues and Sat before 9am and after 6pm
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) Enrol on the City of Cape Town website to submit your water meter readings electronically. Now that tariffs have escalated so sharply, you will want to ensure that you do not get charged based on inaccurate estimates. Also checking your water meter regularly will help eliminate unpleasant surprises in the event of a leak.
2) Check your security. Consider installing locks on any easily accessible external taps. Theft of water is growing and may get substantially worse under Day Zero disruption and confusion. Consider also possible ways in which you may safeguard your swimming pool water.
3) Remain up-to-date with suggestions advice and tips from others on how best to save water and to deal with the many challenges and problems that will arise. Check the Water Shedding Western Cape Facebook group. Details of reliable suppliers are given there and searches of past posts will provide a wealth of guidance and ideas on almost any subject. Member, Dani Nieckau, has set up a website where she’s posting all the hints and tips from this website, all in one easy to read place. Click the link and have a look – some good ideas there!
4) Anne Schlebusch advances some well-thought reasoning about doing away with the “Day Zero” concept. Read about her ideas here. In fact other political quarters are also criticising the term, viewing it as divisive and fear-mongering. Perhaps it is time to come up with a new term. As it seems that we may well get through to winter rains and then the sunny uplands of strong flows of augmented water, perhaps we should refer to a new point in time as “Water Survival Day”, being that day when we are certain that we will never again have to implement rationing/collection systems.
Will the weather help?
The forecast for the coming 6-8 weeks is that the weather will remain sunny and hot through until March where some spells of occasional rain are predicted.
La Niña conditions are still in place. However, climate predictions is that La Niña will fade back to neutral during Autumn.
Here is the rainfall chart for the dam catchments for the period since 1st April 2017.
January 2018 has so far turned out to be a month of below-average rainfall.
In Summary: outflows exceeded inflows by 8.5 M.cuM and combined dam levels fell to 26.0%.
Here are the levels of the six main dams serving the Cape Town/Overberg/Boland area. As may be seen from this table, the four mountain dams still hold more water than they did this time last year.
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 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.