Cape Water and Dams Report

(Wolwedans Dam. Now 75% full. Photo : DWS)

 Dams – Latest levels: Winelands and Cape Town

Report nr. 119 (updated 27th August 2018) on the main dams serving

Cape Town City and nearby Boland/Overberg towns

Excellent widespread rains caused combined levels of the main dams to rise by 19.2 M.cuM (2.2% of capacity) last week. Total water in storage climbed from 59.8% of capacity to 61.9%.

During the same week last year, levels rose by 15.9 M.cuM (1.8%) to 33.9% of capacity.

Useful rains, but nothing special. This graph shows current (Jul-Aug) rainfall continues to be in the same general range as that received in 2017. As we move through the second half of winter, it seems that any hopes of all the dams becoming fairly full is starting to wane. The 4 smaller dams have done well but Theewaterskloof and Voelvlei, although better than 2017, are lagging well behind.

As expected, rains this past weekend caused the stored water level to exceed 550 M.cuM for the first time in two years. So, given that there will be quantities of run-off and snow-melt water still on its way to the dams, I expect that we may well exceed 65% by August month-end.

Putting it into context!

The 4 smaller dams are filling quickly and have on average just exceeded 90% of their capacity. There is every possibility of all four filling and spilling before end of winter. Efforts are being made to transfer water from Berg River to TWK, but at the maximum pumping rate only around 2.5 M.cuM can be shifted each week. Overflow water may therefore soon start heading for the sea.

This highlights the urgent need for the planned additional Berg River transfer facility whereby surplus water coming down the river from the upper dams will be intercepted and pumped up to Voelvlei dam. It is expected that, in good rainfall years, some 20 M.cuM of extra water will thereby be retained in the bigger Voelvlei Dam and kept available to the WC Water Supply System. Hopefully this improvement, now approved to be undertaken by DWS, will be functional by winter 2020.

Augmented water supplies i.e. the difference between the water drawn from the six main dams (471 ML/day) and that consumed from all sources (513 M.cuM) this week stood at 42 ML/day.

(Graph tracking overall use and production of extra water through the augmentation efforts)

Read full report on status of Cape Town’s augmentation efforts here.

How well are we actually doing overall?

The CoCT graph of the combined level of the 6 main dams shows good improvement last week.

Our large inland irrigation dams improved further, with Brandvlei Dam reaching 45.1% and Kwaggaskloof Dam up to 44.4% of capacity. Clanwilliam Dam remains full and spilling and the lower smaller Bullshoek Dam is now over 99%.

Further east the situation is not good. Little of the recent winter rains has penetrated beyond the Langeberg mountain range and towns such as Barrydale, Ladismith, Calitzdorp and others, as well as their surrounding farming communities are in serious trouble. Rainfall in the Klein Karoo area has generally been only one third of normal (anyway fairly low) levels; the area is now experiencing it 4th successive year of drought. And, as much of this has fallen as light intermittent rain, the water has tended to evaporate before it could penetrate the soil. Some parts of the Klein Karoo have received less than 90 mm for the entire year to date (by comparison, Dwarsberg received this much rain in one day last week). Many of these farmers have been forced to sell their livestock and there is a general shortage of feed.

Read more here about a charity that provides help to these needy farmers.

It will be appreciated if you help with donations to cover some costs of distribution this animal feed,

Will the weather help?

Last week the South Atlantic High moved away sufficiently to permit that cold front to penetrate inland and bring good rainfall to all the dam catchments. This improved the overall situation substantially from that prevailing a week earlier. Here is the chart of rainfall received at the dams.

Click here to see ShowMe Winelands Weather forecast of possible near-term rain.

What rain ought we to now expect?

1) A cold front bringing 25-40 mm of widespread rain is forecast to move  across the Cape on 4th and 5th September. This chart shows the potential rain area.

The extent of this rain will be somewhat dependent upon the pressure dropping over the land to permit the front to penetrate into the catchments.

2) Scattered showers are expected occasionally, with 5-10 mm forecast for around 21st September.

3) In general the long-range forecast for September and October does not indicate much rain.

El Nino is continuing to emerge, perhaps a little more slowly and more weakly than originally anticipated.

This NOAA/CPC chart shows the variety of different forecasts that go into producing a combined (so-called “ensemble”) view of how ENSO might develop.

The dark blue line represents the expected outcome. At this time the El Nino (warmer sea temperature) condition is confidently expected to arise, albeit not to such an extreme level/duration as occurred last time.

Nonetheless it points to a probably dryer inland summer season and a possibly delayed start to Cape rainfall next winter.

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What are the authorities doing?

Cape Town City met DWS on Friday last week during which it proposed a relaxation of the water restriction levels, which would in turn “pave the way for the associated relaxation of the restriction tariffs“. The proposal envisaged a reduction in urban restrictions from 45% to 40% and in agricultural restrictions from 60% to 50%. This proposal was supported by the other municipalities in the Western Cape Supply System. DWS has undertaken to respond with a reply by Friday, 31st August.

I have been advocating for some time that if combined dam levels reach 65%, then an easing of restrictions back to level-5 (87 L/p/day) together with a stepping down of the tariff would be justified.

My justification for this is that instead of it being allowed to all spill and flow away to the sea, it is better to supply this ‘surplus’ fresh water to users and to earn more revenue from increased sales, thereby also providing residential and business users with a reduction in costs through the then lower applicable tariff which would also apply. Users are likely to continue to use water conservatively and save costs, but easing restrictions would ease the pressure on older users through possibly reduced physical handling of grey water and permit larger families more generous usage per person.

A word on reported City of Cape Town water revenue ‘surpluses’.

Some commentators recently argued that surpluses are being generated by CoCT through the sale of water at high tariffs, burdening consumers; and that these extra earnings are being squandered.

I have looked into the matter with CoCT Water & Sanitation Dept. and understand it to be as follows.

1) The City is selling more water than budgeted, so it is generating more revenue than expected.

2) However, in the Water and Sanitation budget, the tariffs are not set to recover the full cost. R1.2 billion is subtracted from the cost first which is expected to be covered by transferring income from rates. In other words, the budgeted water revenue would not cover the full budgeted cost of producing and delivering the water. This is a form of subsidy of the water costs by ratepayers. The fact that the invoiced revenue is now exceeding the budget means that water income is closer to the cost (without subsidy) than expected, but this will only be confirmed once invoices turn to cash.

3) To the extent that water revenues may now exceed budget, once this revenue turns to cash income then such surpluses may be used to reduce that R1.2 billion subsidy so that there is less support required for W&S from the rates account.

4) Thus, even with an apparent surplus to budget being earned on the sale of water, the whole cost of water delivery is in fact not covered and some subsidisation from rates is still needed.

5) So, in fact it seems that the consumer is not being burdened as fully as would otherwise be required. And there is no surplus to be squandered.

6) As the water crisis eases, the intention is that the Water and Sanitation operation will return to a situation where its costs are fully covered by its income. That is not the case at the moment.

Summary: Combined levels of the six main reservoirs serving the Cape Town/Overberg/Boland area rose from 59.8% to 61.9% of capacity.

Watch me answer the often asked question: “why do you write this report?“

Read the full City Cape Town release about Water By-law amendments here.

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

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 with a background in Finance and IT; and now a fruit farmer, with a passion for the weather and climate.

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