Dams – Latest levels: Winelands and Cape Town
Latest report (updated 13th November 2017) on the main dams serving
Cape Town City and nearby Boland/Overberg towns
A dry week saw outflows exceeding inflows by 8.7 M.cuM, 1% of capacity of the 6 main dams (vs 5.8 M.cuM net outflow last week).
As a result, combined dam levels dropped to 36.5% of capacity. During the same period in 2016, total dam levels declined by 1.1% to 58.7% of full capacity.
[Why since 1st November 2016? that was when harsher level 3 restrictions were imposed].
Current status?
Total water in the 6 main dams fell to 324.2 M.cuM (240 M.cuM of easily accessible) water (last year this dropped to 522 and 444 M.cuM respectively over the same period). A steady fall in the total water stored may now be expected throughout summer.
The UCT model tracking rainfall at Cape Town Airport (see chart below) shows just how extreme the situation has become. At 141.4mm for 2017 year-to-date (red line), this year’s rainfall has been 31% less than the 206mm received by the same time in 2016 (brown line), the previously worst annual rainfall year across the past 40 years.
Obviously this lack of rain is why we are in so much trouble. Equally, this lack of rain gives the authorities very little scope to deal with the situation.
How long will the remaining fresh water last?
In our model the standard estimate of water remaining at the start of each month is shown in the yellow column. This is calculated assuming the same rainfall and consumption levels as happened in 2016 (blue columns). Based on the actual of 333 M.cuM that remained at the start of November 2017, the theoretical “zero water day” (pink) is estimated to occur around first week of March, 2018.
But as the authorities will likely aim to stretch existing water supplies out to next winter new restrictions may be implemented and water usage will surely be different this season.
My understanding is that the water supply modelling exercise by DWS is finished and that once final adjustments in allocations are agreed, new targets will be gazetted. It may be expected that these will drive household and commercial targets down by 40-50% below the average use over the past few years. Agriculture irrigation allocations may need to be cut by as much as 60%.
Using projected changes to allocations, I have recalculated what the then resultant amount of stored water could be (green columns) each month. This shows that the currently available stored water could see us through to June, 2018.
How are we doing in reality? Pretty well! Given where we stood on 13th November and with general rains still expected over the coming few days as well as next week, it looks like the total water stored at the beginning of December could be as high as 295 to 300 M.cuM. This would be considerably better than the conservative (green) 287 M.cuM calculated just 2 weeks ago (and far, far better than the earlier “business as usual” (yellow) estimate of 266 M.cuM), and would place us on a firm trajectory to survive through to next winter.
What are the authorities doing now?
Given that the Minister of Finance has permitted City of Cape Town to amend its budgets, the mayor reports that, while protecting funds for basic and emergency services, some non-water-related projects have been temporarily postponed and that R2 billion of funds have been re-prioritised to fund CoCT’s first seven additional water projects.
These are: desalination plants at Monwabisi, Strandfontein, the V&A Waterfront, and Cape Town Harbour; the Atlantis and Cape Flats Aquifer projects; and the Zandvliet water recycling project.
See chart below published by CoCT on 19th October 2017 outlining specific interventions planned. The City is now proceeding as fast as possible with “Immediate” and “Tranche-1″ items, aimed to produce 150+ML/day somewhere between Feb and May 2018.
What has already been achieved? To date the City has announced that the following projects have been initiated.
- Atlantis Aquifer abstraction improvements, already contributing 5 ML/d from November 2017
- Orangezicht Springs leading 2 ML/d to the Molteno reservoir from November 2017
- V&A de-salination plant under construction, intended to contribute 2 ML/d from February 2018
- Monwabisis and Strandfontein desal. plant scontracted to produce 8 ML/d from April 2018
- Refitting the Zandvliet water treatment plant to reclaim waste water is under way.
However, at an average of 582 ML/day, water consumption in the City remains too high and substantial extra savings are still needed.
Further afield, the Gamka dam in Beaufort West is dry (see heading photo) and the town is now reliant on those boreholes still operating. There are reports of security difficulties increasing with water being stolen from any external taps that still hold water.
Another worrying aspect that could pose a risk of almost unimaginable proportions are reports that Eskom is reportedly running out of cash. The Daily Maverick report (read it here) states that “without any further funding, Eskom will have about R1.2-billion of liquid assets at the end of November 2017 against a target of R20-billion, and will move into a negative liquidity position of approximately -R5-billion by end of January 2018“. To put this into context, Eskom holds deposits (effectively advances paid to secure electricity services) from commercial farmers which could in total – at a rough guess, for 35000 farmers – easily exceed R3.5 billion. If so, this would mean that as at end-November Eskom would have less cash in hand than it owes farmers in electricity.
Apart from the potential economic disaster, obviously no electricity = no pumping = no water!
What ought households to be doing?
False news and rumours may spread. Stay accurately informed. Join a reliable social media water information group such as FB group Water Shedding Western Cape.
Keep thinking about how you can cope if water supplies cease. The big task will be that everyone needing water would have to go and collect it from some nearby distribution point and then transport and carry that water home. Under these circumstances households will need to cut actual water usage as deeply as possible in order to make water so collected last as long as possible. For example here is a suggested way to cut water used for a shower to under half a litre.
Do create some form of household rainwater capture and storage facility of whatever size you can afford. More rainfall is forecast next week and you could easily capture and store some hundreds of litres as an emergency backup supply for your household. Drawing water from a convenient tank is so much easier than having to fetch and carry tens of litres of water home for household use.
Generally plan ahead for possible water outages; here are points that could help.
Will the weather help?
Occasional rain is expected each week through November, with heavier falls more inland on 14th/15th and then more generally on 21st, which could be accompanied by a thunderstorm. It is expected that this rain may benefit the Theewaters dam.
The recent colder, overcast weather probably also slowed down evaporation from the dams.
NOAA/CPC announced that a a La Niña condition is in effect. Expected to continue for 4-6 months, and benefit ZA’s summer rainfall area, it may also bring unstable and sometimes unseasonable wet weather to the Western Cape.
This chart tracks rainfall at the dams since April 2017. Last week was a very dry week with no meaningful rain falling in any of the dam catchments, so there is no change from last week. However, the coming 7-10 days could see useful rains falling, especially to the benefit of the Theewaters dam.
In Summary: outflows exceeded inflows by 8.7 M.cuM and combined dam levels fell to 36.5% of total capacity. The mountain catchments should enjoy rainfall run-off through the coming week.
This table shows the levels of the six main dams that serve the Cape Town/Overberg/Boland area as reported by Dept Water and Sanitation. It seems that combined water stored ahead of summer has now peaked and an accelerating drop in dam levels may now be expected.
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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