Rain and storm for Cpt

[Agent_Smith]

Looking forward to seeing what the Berg River dam looks like. Circumventing it forms part of this year's Bastille Day trail run. Last year it was almost non existent. This year, crossing the river that flows into it is going to be an experience (in the cold!).

 

[paul5186]

Incredible numbers coming in for Clanwilliam Dam, currently sitting at 89%
In the last 2 days over 20% uplift!

Pity they have not raised the dam wall yet

 

[Rouxenator]

Looking forward to seeing what the Berg River dam looks like. Circumventing it forms part of this year's Bastille Day trail run. Last year it was almost non existent. This year, crossing the river that flows into it is going to be an experience (in the cold!).

Rode round it on the Porcupine Ridge MTB ride for the last couple of years, it did not look too bad. Not as bad as Clainwilliam was back in April.

2016 : https://mybroadband.co.za/vb/showth...phy-Thread?p=17008940&viewfull=1#post17008940

2017 : https://mybroadband.co.za/vb/showth...phy-Thread?p=19060384&viewfull=1#post19060384

 

[Geoff.D]

Pity they have not raised the dam wall yet

Ja that was my first thought. Just imagine how much better off everyone could have been.

 

[saor]

Drone footage of the snow(boarding) in Matroosberg...

https://www.traveller24.com/Multimedia/watch-gorgeous-drone-footage-of-snowboarders-taking-on-matroosberg-20180704

 

[genetic]

It seems we had roughly the same amount of rain for June this year, as we had in 2016 - only slightly up from last year;

http://www.weathersa.co.za/climate/historical-rain-maps

 

[genetic]

Rainfall for June 2018:



June 2017:



Still a far cry from June 2013:

 

[noxibox]

Tables of figures for catchment areas would be more useful for comparison.

Still a far cry from June 2013:

Looks like a wider spread of rain in 2013, but not necessarily where it matters most. The rainfall in June 2018 is indeed about average overall. Above in some locations, below in others. But average is a significant improvement over 2017.

 

[Geoff.D]

The AAO Index

The AAO index reached zero today ( actual measurement). The 7 day forecast is for the index to go positive, so we can expect a drop in rainfall again for a while over the WC. AAO going positive shows a return to summer rainfall patterns with moisture moving in over SA from the North, and cold fronts moving past our shores to the south.
Let us hope that we see a return to negative soon.

 

[Mortymoose]

Clanwilliam Dam two minutes ago as I drove past on my way down to the Cape for a 2nd time in a week..

 

[Geoff.D]

Water movement: Voelvlei Dam

Below is a graph showing a sudden drop in the level of the Voelvlei Dam on the 5th July. Evidence of a water transfer to another dam and system?


Source: https://www.dwa.gov.za/Hydrology/Unverified/DetailStageFlow.aspx?Station=G1R001FW&Type=Flow&Rain=Y

Water outflow into the Breede river system. Spike in the %fill of the Calitz dam a day later.

https://www.dwa.gov.za/Hydrology/Unverified/DetailStageFlow.aspx?Station=J2R001H3T&Type=Flow&Rain=N

 

[Gordon_R]

Below is a graph showing a sudden drop in the level of the Voelvlei Dam on the 5th July. Evidence of a water transfer to another dam and system?

ATTACH 534833
Source: https://www.dwa.gov.za/Hydrology/Unverified/DetailStageFlow.aspx?Station=G1R001FW&Type=Flow

Water outflow into the Breede river system. Spike in the %fill of the Calitz dam a day later.

I don't know the reason for the drop, but it has nothing to do with the Calitzdorp Dam, which is hundereds of kilometers away, and in a completely different river basin.

Most likely it is a recalibration of the gauge level, since Voelvlei is shallow and muddy, so small differences in the depth will have a large effect on storage capacity.

Edit: If you look at the 'raw' data, you see an abrupt transition at exactly 2pm on Wed 4th:

2018-07-04 14:00 12.478m 54.400%
2018-07-04 14:12 11.628m 47.824%

Edit: The depth of the reservoir has been recalibrated by exactly 0.85m.

P.S. Thanks for the link. I did not know there was a real-time gauge at Voelvlei.

Edit: Real-time gauge for Theewaterskloof as well: http://www.dwa.gov.za/Hydrology/Unverified/DetailStageFlow.aspx?Station=H6R001FW&Type=Flow

Edit: These numbers are also uncalibrated, refer to CoCT for calibrated figures.

 

[Geoff.D]

I was looking for a reason for the sudden drop in figures. It was so sudden that it seemed impossible for this to be explained by water release down river. So I sort of assumed it could be a deliberate pumping of water between river basins.
Thanks for finding evidence that it was a recalibration exercise.
This is really careless of the authorities! Why would it be necessary to do this?
Did they have two guages in use? Why did they not ensure the two gauges were synchronised in the first place?
It smells of manipulation of data. A dam does not suddenly change depth by itself.
Hopefully they will now ensure that this sort of data tampering stops.

 

[genetic]

I was looking for a reason for the sudden drop in figures. It was so sudden that it seemed impossible for this to be explained by water release down river. So I sort of assumed it could be a deliberate pumping of water between river basins.
Thanks for finding evidence that it was a recalibration exercise.
This is really careless of the authorities! Why would it be necessary to do this?
Did they have two guages in use? Why did they not ensure the two gauges were synchronised in the first place?
It smells of manipulation of data. A dam does not suddenly change depth by itself.
Hopefully they will now ensure that this sort of data tampering stops.

:wtf:

Careless for the authorities to calibrate their equipment???

 

[Sinbad]

:wtf:

Careless for the authorities to calibrate their equipment???

To allow it to go so far out of whack

 

[genetic]

To allow it to go so far out of whack

With recent the mass influx of water, a lot of sediment can rise in an incredibly short space of time. Also, calibration on equipment happens at set intervals. Geoff.D is making something out of nothing.

 

[Gordon_R]

No new rain until the next cold front on Thurs 12th, when 25-50mm of rain is predicted for the SW-Cape.

Good news on the dam levels for last week (including the heavy rain on Mon 2nd), up 5% overall to 53.3%:
http://resource.capetown.gov.za/doc...ity research reports and review/damlevels.pdf

There is some divergence in the rate at which the major dams are filling, during a period of gradual runoff and limited rain:
Berg River up 4.4% to 83.1%
Theewaterskloof up 4.3% to 39.0%
Voelvlei up 9.4% to 51.4%

 

[Geoff.D]

Mixed signals from the various models on what we can expect from the cold front. Some show it skimming past, others show it moving far inland and others say the inland rain is actually as a result of an upper air low pressure trough extending down the west coast.

 

[Rouxenator]

So.... rain tomorrow?

 

[TheMightyQuinn]

So.... rain tomorrow?

90% chance and 80% for Friday.

NW has been blowing warm the whole afternoon.