Cape Town 90 days away from running out of water

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Simon Culling
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Re: Cape Town 90 days away from running out of water

Unread post by Simon Culling »

October has been rather dry up until mid month with just 3.2mm at the airport site up to the 15th. Not much respite in prospect this week as the forecast is dry until early next week - and warming up to around 30*C by then.

Incidentally, the mercury hit 32.4*C on the 8th at the airport site. The evaporation rate will now be soaring and it will be interesting to see how the reservoir levels fare through the upcoming summer.
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Re: Cape Town 90 days away from running out of water

Unread post by Simon Culling »

The total rainfall for October for the Cape Town Intl Airport site was just 5.2mm from the synops, which is well below average. They have had plenty of hot sunny weather as well, with the temperature at the airport reaching 36.0*C on the 22nd and 35.9*C on the 23rd.

Looking forward, apart from a few showers this weekend, it looks mostly dry although not as hot.

The link below is to a comment article in Nature magazine and is well worth a read as it could apply to many other cities in the world. Here in the UK, we have seen droughts in more southern parts in the last 50 years that led to water restrictions, and the next one will be harder to deal with as we use more water per person nowadays, despite improvements in the water efficiency of domestic machines.

https://www.nature.com/articles/d41586-018-05649-1
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Re: Cape Town 90 days away from running out of water

Unread post by Simon Culling »

The rainfall total for November for the airport site was just 8.5mm from the synops, which is again, well below average. The linked reservoir level report indicates other locations in and around Cape Town received between 5-27mm which is around a third of the LTA. Reservoir levels peaked in mid-November and are now falling as consumption edges up slowly.

https://resource.capetown.gov.za/docume ... levels.pdf
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Re: Cape Town 90 days away from running out of water

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The rainfall total for the Cape Town airport site for December from the synops was 14mm, which is again a little below average - however, this is the dry part of the year so any rain that falls now has little impact on the water resource. Looking at other sites there does seem to be quite a range in totals, but I do not know the accuracy levels of these statistics. So far in January, there has been just a few light showers in the Cape Town area giving just a trace at the airport site.

Rainfall starts to pick up in March/April, so it will be interesting to see the comparative water resource levels at this time. Water consumption (per person) has continued to be much lower than before the drought concerns - but how long will this last?
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Re: Cape Town 90 days away from running out of water

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Only 10.5mm of rain at the airport site for Cape Town in January, although the monthly average is only around 15mm so not a lot would be expected. No rain has been recorded for February so far and the temperature reached 36.9°C on the 7th. The 7-10 day forecast is for a continuation of the dry and sunny weather with temperature dependent on the wind direction.
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Re: Cape Town 90 days away from running out of water

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Rainfall for February was low again at the Cape Town Airport site - only 4.5mm fell, which compares to an average of around 17mm for the month. However, March has started on a wetter note, with 24mm having fallen up to the 15th which is already above the monthly average of around 20mm. Only a few showers are expected in the next week or so.

Dam levels are much healthier than recent years with a quoted figure of 52% for the water stored in the major dams in the Western Cape for the week ended 10th March 2019. This compares to figures for the same date of 22% and 31% for 2018 and 2017 respectively. Water consumption has lifted a little from its lows in 2018, but is still at only 605Ml/day for the week ended 10th March and this compares to a figure of over 1200Ml/day in 2015, before the water crisis became a problem.
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Re: Cape Town 90 days away from running out of water

Unread post by Simon Culling »

The final rainfall total for the Airport site at Cape Town was 27mm (from the Synops) for March, which appears to be a little above average. There is a paucity of data for South Africa - on the official Met Office site for the country, I can find daily figures, but not any monthly ones, and I expect there will be quite a range of rainfall figures for the Cape Province as much of the rainfall appears to have a convective element.

April usually sees the start of annual rains, and so far this month, the synops show 8mm for the airport site.
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Re: Cape Town 90 days away from running out of water

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The April rainfall total for Cape Town Airport was just 24mm according to the synop summaries. This is somewhat below the monthly average of approx. 40mm. Slow start to the winter rains.
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Re: Cape Town 90 days away from running out of water

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There had only been 11mm of rain at the Cape Town Airport for May up to yesterday, but 28mm has fallen from a cold front today which will help. The average for May is usually around 70mm, so the total is still well short of this mark. There is nothing more in the forecast up to the end of the month and a below average rainfall total for this winter will put them back into water restrictions next summer.
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Re: Cape Town 90 days away from running out of water

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The final total rainfall for the Cape Town Airport site for May was just 41.2mm which is well below the average of about 70mm.
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Re: Cape Town 90 days away from running out of water

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The rainfall total for Cape Town Airport for June 2019 is an estimate as some of the data appears to be missing from the monthly summary on Ogimet. The cumulative figure is 57mm, but approx. 20mm fell between the 22nd to the 24th and this gives a monthly total of approx. 80mm. This appears to be a little below the monthly average.
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Re: Cape Town 90 days away from running out of water

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The rainfall total for July at the Cape Town Airport site was 103.7mm from the synops, so some way above the average of around 77mm.

Major dam capacity (as at 29th July) was 72.1% which is the highest level since 2014. Daily water usage has also stayed on target and well below the level before the crisis started. They have gained some breathing space.
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Re: Cape Town 90 days away from running out of water

Unread post by Simon Culling »

An update on the Cape Town rain + dam reserves situation. Rainfall figures for the Airport from the synops were low for both August + September 2019 with totals of 28.4mm and 13.5mm respectively which are way below average. There has only been a trace so far October, but I am not sure of the accuracy of these readings.

The dam storage level for the major dams was 80.6% as at 14th October which compares to a figure of 37.5% for the same date in 2017 - so a massive improvement in the last two years as consumption levels remain close to the target of 650Ml/day. Water levels have begun to fall slowly as the dry season kicks in.

Attached is a link to a recent paper (currently on free access) which gives a good historical rainfall account for the Cape and the suggestions of a link between Hadley Cell expansion and rainfall intensity from winter cold fronts. The pdf can be downloaded.

https://www.nature.com/articles/s41612-019-0084-6
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Re: Cape Town 90 days away from running out of water

Unread post by Simon Culling »

A cold front has brought heavy rain to the Western Cape overnight and through Friday 25th October - totals in and around Cape Town of 50mm+.

https://twitter.com/SAWeatherServic/sta ... 9222887425

https://twitter.com/StormReportSA1/stat ... 4277758977

The cricket ground at Newlands is looking a bit damp!!

The average rainfall for October for the Cape Town city area is only about 30-40mm.
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Re: Cape Town 90 days away from running out of water

Unread post by Simon Culling »

The rainfall total for the Cape Town airport for October 2019 was 62.4mm with most of this falling on one day. This appears to be at least 150% of the monthly average.

The major dam storage level for the Western Cape as of 11/11/2019 was at 84% which compares with just 37% on the same date in 2017. Quite an improvement. Average daily water usage is running at 675Ml/day and this compares to a figure of roughly 1100Ml/day in 2015.
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Re: Cape Town 90 days away from running out of water

Unread post by Simon Culling »

It is winter again in Cape Town, so I thought that I would look to see how it is doing with regard to rainfall and stored water. It is 9 months since we have looked at this issue.

Rainfall at Cape Town Airport (from the synops) was 67mm in June which is quite a bit below the average of around 90mm. However, July has been wet so far, with 151mm up to the 16th, which is nearly double the July average of about 80mm. This will feed into the dams over the next few weeks.

The latest report on dam levels, for the week ending 13th July, shows the major dam storage level is at 72.7%, which compares to 61.4% at the same time last year. They have also managed to keep average usage to around 650Ml/day.

The weather has certainly helped them out, but they have made a lot of progress on eliminating waste - much to learn here by other nations.
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Re: Cape Town 90 days away from running out of water

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This is a novel approach to solving a drought crisis - cut the trees down.

There is a little bit more to this story than the headline might suggest.

https://www.bbc.co.uk/news/world-africa-59221823
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