Dams – Latest levels: Winelands and Cape Town (7Aug)
Latest report (updated 7th August 2017) on the main dams serving
Cape Town City and nearby Boland/Overberg towns
As predicted, good rains last week in the Wemmershoek and Berg River dam catchments caused both dams to recharge well, helping the overall net inflows to reach 13.0 M.cuM for the week (1.5% of capacity). Combined total water stored rose to stand at 29.0% of capacity.
Last year the dams levels rose by 51.1 M.cuM (3.5X more) during the same week to reach 53.5% of capacity due to heavy rains at that time.
The year-on-year comparison shows that net water used in 2017 is now 118.8 M.cuM higher than that used in 2016, the difference being due to much higher rainfall at this time in 2016. We are starting to fall seriously far behind.
[Why since 1st November? that was when level 4 restrictions were imposed].
Current status?
There is now 257 M.cuM (172 M.cuM of easily accessible) water in the dams (last year same time this stood at 478 and 393 M.cuM respectively).
So: we now only have less than half as much water than we had last year to meet our needs .
The situation is becoming very alarming. Rain is simply not arriving as it usually does at this time of year. August will be absolutely critical. Unless very heavy rains arrive there is not much else to hope for this winter. And according to current NOAA/CPC climate forecasts, only 10-20 mm may be expected in the mountain catchments this coming week, and less than 10 mm the week after. So it is now increasingly probable that we not will reach 300 McuM of total water stored in the 6 main dams by the end of 2017 winter.
How many days of water are left?
At the low winter usage rate estimated at 6.2 M.cuM per week, theoretically we now have 28 weeks supply on hand at current consumption rates.
But the consumption rate will soon start to rise as the summer factors and agricultural irrigation start to kick in. Unfortunately, in my opinion it now appears that we could end up with a total of less than 300 M.cuM in storage at the end of winter. Without a reduction in the summer consumption patterns, it would mean the water then being exhausted by early- to mid-January 2018.
If things continue like this clearly the authorities will have to act yet more vigorously to curb consumption.
If we are to make it through to early winter 2018, all forms of water consumption will have to be reduced more sharply. It can be done but it is going to be rather unpleasant!
Read here what steps we believe authorities need to take to ensure sufficient potable water is available until winter of 2018.
Farmers will face very difficult decisions already within 3-4 weeks when their irrigation programs would normally start up. Indications already are that irrigation water allocations may be reduced by 30% or more. It will not be easy for producers to decide which 30% of their trees to starve of water. And the point is this: once water is withheld, blossoming and fruit setting will fail; so even if it later rains well, there will be no fruit left on those trees to use the rain this coming season. One cannot put the blossoms back on the trees – once the flowers have fallen the season is over for those trees.
So many farmers will have to confront “zero water day” within a few weeks. Read more here about what the consequences for these important food producers can be.
What ought households to be doing?
You should now start to plan to deal with further sharp reductions in water availability. I expect targets to soon be reduced below 50L/person/day. It is also possible that at some stage water outages will start to occur.
What to do? My advice remains the same as it has done now for over a year; make your household more water-resilient;
- Practice getting by using far less water (read my suggestions on how to).
- Install some means to harvest and store rainwater so that you have additional flexibility and control.
But please do something as soon as you can – extra restrictions are sure to come into place soon.
What are the authorities doing now?
No useful information is coming from CoCT other than the usual exhortation to reduce consumption. In absolute fairness they do not control the weather and few would have forecast so deep and prolonged a drought. But, to date there has been little visible effort to mobilise the wider population in a positive manner.
We are just told that the City is considering recent RFI responses but without giving any indication where they may be leading or what relief any of the proposed measures may bring.
And the long-promised operational plan for possible “Zero water” conditions is yet to be published.
It is hard not to become angry that, in the face of what may turn out to be one of the most severe natural calamities to face a modern city, the City of Cape Town is failing dismally to take it citizens into it confidence, leaving speculation and anxiety to grow in the vacuum.
Will the weather help?
It is now all about the weather. If it doesn’t rain solidly in the catchments over the coming 3-5 weeks then the crisis will be upon us and survival will become the name of the game.
So what weather is on its way?
One cold front will strike the Cape around midnight on Thursday night and bring some 20-30 mm of rain through till Friday evening,
Again we may expect Wemmershoek and Berg River Dams to be the main recipients.
This NOAA/CPC chart shows the cumulative amount of rain that may be expected between 11th and 12th of August.
Nothing more than 10 mm of rain is forecast for the week after that.
As can be seen from this chart, the heavy rain is once more moving through some 600km south of the Cape.
What else may we expect?
It seems that late August will bring several bouts of rain to SW Cape.
- 10-15 mm rain across 21-22nd August
- 20-30 mm of rain over 27-28th August.
- 30-40 mm of rain during the 1st week of September.
after that through September just short spells of light, occasional rain are forecast.
So at best, August and September may bring just normal average rainfall. This is unhelpful when in fact it is “near-floods” that we need.
Unfortunately, El Niño which had indicated a flicker of hope that a La Niña might start to develop, seems to be persisting in neutral range. So hopes of help from that quarter now seems to be fading as our southern winter starts to come to an end.
The latest historic rainfall chart for Cape Town Airport produced by UCT (find it here.) indicates that this 2017 rainfall is now the worst for the past 15 years covered by their chart. It is somewhat depressing to see how the rainfall built up far more quickly in 2016 that it has this year.
How much rain has fallen in the dam catchment areas? Last week the good rains boosted the mountain dams, much as it did the previous week. All are benefitting somewhat from rainfall run-off while Steenbras Upper also benefitted from water transferred from Rockview dam.
Sadly, July 2017 brought less than average rainfall across the whole system. And one can now see that, apart from Steenbras Upper, the different dam levels are in fact little changed since the end of April. All hopes now rest on a strong rainfall pattern during 2nd-half August and first-half September.
In Summary: fresh rains and net inflows continued, yielding 13.0 M.cuM rise in the dams levels, up from 27.5% to 29.0% of capacity. Further rains this coming week may help. Dam levels are becoming disastrously low. Constant water savings is essential.
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.
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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