Cape Dams Levels – weekly report (008)

 ShowMe Winelands

Cape Dams Levels – weekly report nr. 008

as at 17th December 2018

                                        [De Bos Dam. Currently 61% full.  Photo: DWS]

It is all proceeding much as anticipated. The small amounts of rain over the past few days brought little change to the main dams, although the cooler weather may have moderated evaporation a bit.

Net outflows from the main SW Cape dams rose week-on-week to 11.0 M.cuM, 1.2% of capacity, while combined water in the 6 dams fell from 613.5 M.cuM to 602.5 M.cuM; i.e. from 69.0% to 67.7% of overall capacity. During the same week last year the total volume stored fell by a similar 10.1 M.cuM (1.1%).

As the number of visitors increases we may expect weekly net outflows to climb towards 15 M.cuM.

Here are the levels of the 6 main main dams.

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Use of water from the dams by the Metro residential and business users also did rise to 560 ML/day, probably reflecting a tentative increase in use and relaxation of savings by some residential consumers. What it also seems to indicate, though, is that many residential users have stuck to their previous water savings practices.

This increased use is good, as the new lower tariffs in effect since 1st December actually assume that average usage will rise to 650 ML/d in the Metro. But if overall usage does not rise to around the budgeted levels then a revenue shortfall may result. So if the usage does not increase sharply – as it may well do when the wave of visitors arrives – then we may expect further relaxation by the authorities of usage limitations (e.g. permit watering with hoses and the topping of pools) to be announced by end-January, 2019.

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The graph below charts weekly water consumption shown by the net change in the water stored collectively in the main dams. It can be seen that weekly net outflows from the main dams are tracking very similarly to the net outflows during the same weeks in 2017. Agricultural irrigation use is climbing, as it must at this time of year, but residential water use remains very subdued.

The people of the SW cape are to be congratulated on this wonderful outcome and for removing excess demand from the system. If this pattern is maintained out into the future then it will provide the authorities with valuable breathing space to bring new water production facilities into existence, while allowing business activity to climb and agriculture to resume its important contribution to regional economic activity and job creation.

                                                          [click on the graph to see an enlarged version]

Read here about the revised Cape Town water restrictions operative since 1st December 2018.

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There are no major weather systems predicted for the coming six weeks. The South Atlantic High is expected to move away allowing some light rain to penetrate on Boxing Day, bringing perhaps 2-4 mm depending upon which cloud you may find yourself under.

El Nino continues to form and may slow rainfall inland as summer progresses. I do have a small concern that it is predicted to persist into autumn/winter 2019 and that may delay the onset of our next winter rains. We shall see.

With most folks now on leave there are unlikely to be any material developments over the coming few weeks. It therefore remains only for me to wish readers a blessed, calm festive season and a safe, more prosperous and less stressful New Year than the year that we leave behind us.

Thanks to all of you who have commented regularly and intelligently on the many issues that we have examined this past year. You have added interest to my series of articles and your participation has been truly appreciated.

To remain fully informed you may like to check the following items weekly

• City of Cape Town weekly “Water Dashboard“, to be found here.
• Our 7-day & 24-hour weather report here shows probable rain in Boland dam catchments.
• SA Weather Services current Synoptic Chart here showing the currently developing weather.
• Look at our supporting current monthly report here.