Dams – Latest levels: Winelands and Cape Town
Latest report (updated 15th January 2018) on the main dams serving
Cape Town City and nearby Boland/Overberg towns
Water consumption last week dropped marginally to 9.6 M.cuM, 1.1% of total capacity; vs the preceding week’s 10.6 M.cuM. Combined dam levels dropped from 29.5% of capacity to 28.4%.
During the same period in 2017, the main dams dropped by a hefty 15.5 M.cuM, with the dams sinking by 1.7% to 42.0% of full capacity.
The graph of the weekly change in stored water, 2017/18 versus 2016/17, is starting to show a steady consumption pattern that is substantially less that the same periods in 2016-17.
Current status?
Combined water stored in the 6 main dams fell to 252 M.cuM (167 M.cuM of easily accessible water) (last year, levels dropped to 374 and 289 M.cuM respectively over the same period).
Notwithstanding the steady drop in dam levels, as may be seen below, in my opinion the probability of “Day Zero” happening this autumn are diminishing.
How can that be? Well there are two main reasons:
Firstly, water savings by households and businesses seem to be starting to have a distinct impact. Consider this: in the first half of January last year, SW Cape water consumption was some 40 M.cuM while in the first two weeks of January 2018, the consumption was 20.2 M.cuM, barely half that of same time last year.
At a personal level, the ‘coarse average water use’ is around 144L/pers/day. But if one then deducts the amount used by businesses as well as the so-called “non-revenue water”, i.e. that lost through leaks, unmetered use, theft, etc, then the coarse average drops to around 95L/pers/day. So it appears that we, the ordinary folks, are actually doing a pretty good job? Or are we? To be fair we ought to add back the showers taken at the gym, use of toilets, basins and tea at the workplace. So a fair actual average consumption is possibly more like 110L/pers/day – do you agree? So further savings can be achieved by being as thrifty with water at the office or factory as we are at home.
Secondly, savings in the agricultural sector are starting to play their part. Remember that the agricultural allocation has been cut by 60% (vs the 40% reduction for households and businesses).
Now, while flows of water to irrigation may still seem high relative to the reduced allocation (dotted line), this graph issued by CoCT shows that the rate of consumption is starting to flatten. DWS advise that growing numbers of users are being switched off, so the heavy line should flatten more and more indicating when the ceiling of agricultural allocation has been reached.
Some readers feel that water to farmers could be cut even further but the drought’s impact is already causing lower product quality and 20-30% financial losses. For farmers, “Day Zero” has already arrived.
One important point to remember about farming is that one cannot grow half a peach or quarter of an apple. It is all or nothing. So there is no point to drag out the water supply, but better to give what is available at the full normal rate so that the best use can be made of it and at least some crop can be produced before the valves are closed. In the end more or less the same amount of water will be consumed, but this way the outcome for the farmers can be optimised.
DWS states that there may be a small (10%?) overshoot in agricultural water use. Why? Well some of the irrigators with early crops had in the normal course of events already exceeded their 40% in the months before the new restriction was introduced. That water, naturally, cannot be recovered. Also there are some losses during water distribution which will need to be absorbed.
As one sees from this graph from CoCT, the outcome is that agriculture is consuming only slightly less water than the metro at the moment. However, expect that to start to alter sharply as agriculture draw-down diminishes over the coming 2-4 weeks.
Of course the drought is hammering the farms and rural communities. Farm employment dropped in 2015/2016 by 35,000 (-14%) from 250,000 to 215,000. Last year (still to be published) will have seen a similar drop, worsening the situation still further.
In summary: the SW Cape agricultural industry has been placed under enormous pressure in order to ensure that sufficient water is kept in reserve for the residential and business sectors. Is this fair on agriculture? Yes; irrigators pay less for their water (their cost of raw water is around half of that charged to the municipalities); and that, in turn, is because cities pay for a higher committed level of water security of 97% whereas for agriculture the water security commitment is only 71%. It is at times of stress like this that the parties finally receive the value that they pay for.
What should you be doing?
Do beware of misinformation, and worse, disinformation (“fake news”) that will surely be finding its way on to social media. As suggested last week, be sceptical and double-check any unexpected or sensational items, particularly any information that deliberately angers or upsets you.
Two recent examples “false news” items;
1) a FB post stated that a sluice gate at TWK dam was faulty, not fixed and wasting huge amounts of water. What rubbish. It’s a valve releasing water for towns downstream which get water from TWK.
2) a news item this week stating the dam levels had fallen by over 3%. It was just a typo, should have been 1%. It’s unlikely that dam levels would ever drop by 3% in one week (unless a dam burst).
But both items generated a bunch of heated, sometimes very derogatory comments. Don’t be fooled. If uncertain, ask your FB water group for confirmation. Expert members will help you out.
How long will the remaining fresh water last?
The water consumption across the entire SW Cape as supplied from the main dams remains at gratifyingly low levels. So much so that I have revised my predicted net use for January down from the previous 63.6 M.cuM to 42.4 M.cuM. If this eventuates, it would mean that we could end January 2018 with a combined 230 M.cuM of water still stored across the system.
Clearly, people are doing what they can to reduce water consumption. So, take a bow all you water warriors; you are doing a great job. But don’t relax – keep saving and encourage others to do so.
Unless something completely unexpected occurs, it seems that we can be increasingly confident that the existing water supplies stored in the dams will last us through to June. It also indicates that the authorities should be able to defer implementation of the rationing/collection stage-2 of the disaster plan (forgotten? read details of the three stages here) until June. And by then the extra water production should be starting to ramp up, supplemented by early winter rains.
What are the authorities doing now?
City of Cape Town reported that the amount of water it drew from the dams jumped sharply by 7% to an average of 598 ML/day (from 559 ML/day) while the water used from ‘all sources’ climbed to 618 ML/day. This is an unwelcome change as it means the metro’s water consumption for last week was 15% above it’s revised allocation. No reason has yet been given for the jump. Seeing that total SW Cape consumption declined from last week, it is unclear why the metro bucked this trend.
The good news is that water generated by the City was 20 ML/day from its own facilities. This amount of extra production should gradually climb as additional augmentation initiatives come into production, hopefully rising more quickly after April.
Regarding ground water abstraction, we are informed that drill rigs have moved onto location on the Cape Flats and have commenced drilling and encouragingly are encountering the anticipated underground geology. Some concerns have been expressed about the dangers of over-abstraction and of allowing salt water to contaminate the Cape Flats aquifer. Expert advice of geohydrologists is being followed to only abstract water in sustainable volumes while using fresh water barrier techniques – like at Atlantis – as needed to alleviate salt water ingress risk.
One very positive aspect of using ground water is that its quality is similar to that from the dams and therefore the disinfection and purification task can be handled by existing water treatment works, which should have plenty of spare capacity in hand. As the survey findings are so positive, funds are being diverted so that this project can proceed with speed to “harvest this low-hanging fruit.”
Other projects are not cancelled and the temporary desalination plants at Monwabisi, Strandfontein and the V&A Waterfront continue to progress. Others are on hold until a full assessment can be made of groundwater potential. The point is simply that groundwater is less expensive to process and therefore, according to Peter Flower, Director of Water Matters at CoCT, more fresh water can be produced for the same expenditure than with desalination.
DWS is also active with two emergency programs.
1) There is a problem at Voelvlei Dam in that the point where water is abstracted for the Swartland is no longer covered in water when the level falls to below 12%. To remedy this R15m is being invested to install pumps that will lift water from the deeper part of the Voelvlei dam to this abstraction point.
2) A similar problem exists at TWK Dam where the abstraction point for the tunnel through to the Berg River no longer operates. DWS is standing ready with material and equipment on hand to create a berm at the road bridge enabling water to also be lifted from the deep side of the dam so that it can supply the abstraction point to the Cape Town side once that dam level falls below 14%.
In both cases, the intention apparently is to be able to draw the dams down to levels of around 6% if necessary.
That said, DWS has found that when dams fall below a certain critical level, the temperature of the increasingly stagnant water rises, promoting algae growth causing fish to die and rot. Consequently the last of the water can thereby become toxic and unusable.
The extended window for public submissions is now closed and we await the outcome of the public participation process regarding the proposed “drought charge”. Based on comments posted on social media, it seems that public opinion is firmly against imposition of more charges, and especially any that are progressive tax-like charges based on property valuations. Did you have your say?
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.
Lastly, City of Cape Town has done much to add additional graphically presented information regarding the water situation in the City and across the SW Cape. This is 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.
Will the weather help?
The cool La Niña now seems firmly in place. Looking forward, expert opinions feel that it could now continue through our winter.
However, the favourable cool La Niña may not be as helpful as in the past; I was astonished to recently learn that the average low temperature of La Niña is today often hotter than the warm El Niño used to be some decades ago. Such is the effect of climate change.
There was some very light rain over last weekend, but unfortunately little or nothing fell in the catchments – typical summer weather.
More widespread rain should fall from midday 21st to evening of 22nd January, 10-15 mm in the Voelvlei catchment, as much as 20 mm falling near Theewaters, Wemmershoek and Berg River Dams and 30-50 mm falling at Steenbras. While this won’t recharge the dams, such useful rain should hopefully offset evaporation during that week.
There are no other significant weather systems forecast through to end-February.
In Summary: outflows exceeded inflows by 9.6 M.cuM and combined dam levels fell to 28.4%.
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 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.
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