Dams – Latest levels: Winelands and Cape Town
Latest report (updated 6th February 2017) on the main dams serving
Cape Town City and nearby Boland/Overberg towns
Combined water stored in the six main Cape dams fell to 36.9% of overall capacity (down from 38.5% last week).
Net outflows from the six main dams during this past week increased to 14.5 Million cuM vs the prior week’s reported net outflow of 13.2 Million cuM. While back down to pre-holiday season levels the increase of water consumption this last week over that of the previous week disappoints.
The deterioration happened just as tighter level-3B restrictions came into effect on 1st February. Hopefully, the beneficial effect of the new restrictions will show up as a reduction next week.
This accelerated rate of consumption, if continued and heavy rains do not fall in the catchment areas, will exhaust the water in the main dams around the end of May, 2017.
Year-on-year the total water used since 1st November is 21.5% less than for the same period last year. Since level-3 restrictions were imposed, we have collectively consumed some 28 McuM less water than last year and in the process have ‘saved’ around two weeks worth of water; which could prove critical if we are to last through until the next heavy rains arrive. But more savings would help.
What are the authorities doing?
Level-3B restrictions were implemented by Cape Town Municipality on 1st February 2017.
Read here about the new level-3B restrictions and what it may mean for you.
According to News24, Mayor Patricia de Lille has started a routine of personally calling businesses, hotels and government departments to check on their water usage, the City of Cape Town said on Monday. She had contacted several major commercial consumers to inform them that their water consumption was extremely high, and at a level the city could not afford.
“I am advising them to reduce their consumption immediately,” De Lille said in a statement. She urged all residents to use less water. Warning notices would be issued to the metro’s highest domestic, commercial and government water users. Level-3B water restrictions were implemented on Thursday, allow the City to now issue fines of up to R5 000 to residents contravening water restrictions.
Looking ahead.
How long will the water currently stored in the six main dams last? At present usage rates, approximately 114 days (about 16 weeks) until 30th May.
Will the weather help? The long-range forecast still shows a spell of unstable weather at the end of February but the likelihood of good rains seems to have weakened. There will probably still be some rain but it is unlikely to be very extensive. Let us hope that this changes.
Occasional rain only is predicted for March; like February, March is a typically dry month with an average of less than 10mm of rain in the Boland.
The long range forecast for April is starting to indicate various bouts of rain. This would be typical for that time of changing weather patterns and is probably the earliest time at which we can expect useful rains. According to statistics, however, rains in the Boland and mountains tend to come later than they do on the Peninsula. And to help the dams, the rains must fall in the mountains.
And, as an official of the Breede-Gouritz water Management Area reminded me last week, even if good average rains fall this winter it could take the dams three to four years to recover. So restrictions may well be in place for several years to come.
Your comments and concerns.
Many remain concerned about apparent abuse and waste of water. In Cape Town you may report instances to the municipality on Email: waterTOC@capetown.gov.za Telephone: 0860103089 (choose option2: water-related faults) or SMS: 31373 (max 160 characters).
Some of you wonder about desalination plants and why they are not being built? Well, some smaller units have been built, e.g. at Mossel Bay and Lambert’s Bay (read more about ZA’s desalination initiatives here). There may be some justification to build a smaller plant to produce some of the water needed for Cape Town but the cost would be high.
Some readers repeat low cost figures for Israeli water production but the fact is that desalination is an expensive and complex process. We are not experts, but to put this into context; very roughly, at cost rates derived from other similar projects, our calculations are that a desalination plant big enough to produce the 1.1 McuM per day of potable water consumed by the SW Cape area would incur a capital cost of some R11 billion. Additional power generation capacity would be needed and this, on the scale of the new Medupi power station, could cost capital R9 billion [the alternative solar power generation would need about 9x “Jasper” (the recently commissioned ZA Solar power facility) and that could cost almost R20 billion].
So the two plants alone could cost around R20 billion, take 7 to 10 years to build and make operational, and could perhaps incur another R2 billion per year for the operating costs (a big part being fuel for power generation).
‘Surely solar power would use no fuel’ I hear you ask, but solar energy is only available some 8 hours per day while the desalination plant would need to operate 24/7; conventional electricity is needed.
What if we built a plant just big enough to provide 20% of our water needs to help see us through in dry times. It would cost us ‘only’ R4 billion.
Well, we have already saved more that that (21.5% in fact) just by reducing consumption at a small cost, relatively speaking. If we really tried hard we could save 30% or more and completely avoid having to spend the equivalent R6 billion to build a new desalination plant to produce that water.
Our conclusion.
We believe that the lowest cost and fastest way to improve the situation is a combination of:
* Reduce consumption consistently 20+% by implementing simple grey water re-use systems.
* Install roof rainfall capture to tanks in all suitable households and industrial sites.
* Install sustainable water abstraction from the Cape Flats aquifer for backup in drought conditions.
In our assessment, the key factor is that the Cape usually gets decent rains every year, but that it does not always fall heavily in the main dam mountain catchment areas. Therefore the best system should be one that captures and stores the water where it does fall, i.e right where people live. And the Cape aquifer, which also gets replenished every winter, can be sustainably used as an emergency reserve for very dry times.
If we did this, the demand for fresh water could drop by as much as 40%-50% and the water stored in the main dams then would last for up to 4 years instead of the current 2 years in times of drought.
In Summary: outflows exceeded inflows over the week – stored water volume fell from 38.5% to 36.9% of capacity. The water usage rate climbed versus the previous week.
Here are the levels of the six main dams that serve the Cape Town/Overberg/Boland area. Also shown is the total water storage level of all the dams in the whole greater Western Cape.
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).
Read about South Africa’s desalination policies and initiatives.
Read new level-3B water restrictions here.
Read about a D-i-Y household rainwater harvesting and storage system here
Read our water-wise landscaping and water-wise gardening suggestions.
Click here to see Winelands Weather forecast of possible near-term rain.
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