Rain and storm for Cpt

[saor]

Starting up in southern suburbs with heavy wind and rain.

 

[Gordon_R]

20mm in Kenilworth up to 8pm.

Edit: 77mm on SAEON Dwarsberg (Jonkershoek) up to midnight.

 

[air]

Edit: 77mm on SAEON Dwarsberg (Jonkershoek) up to midnight.

Yep, very decent number in about 7 hours - SAEON website has been dodgy last day or two.
Bucketed down in Gardens last night and then a bit more this morning.

Was reviewing this earlier -> http://www.dwa.gov.za/Hydrology/Unverified/UnverifiedDataFlowInfo.aspx

 

[Gordon_R]

Yep, very decent number in about 7 hours - SAEON website has been dodgy last day or two.
Bucketed down in Gardens last night and then a bit more this morning.

Was reviewing this earlier -> http://www.dwa.gov.za/Hydrology/Unverified/UnverifiedDataFlowInfo.aspx

Another 6mm overnight in Kenilworth. More rain predicted for this evening, and at times during the rest of the week.

The DWA numbers for the W-Cape are a mishmash of data-points, not very representative of the major catchments.

The only one that has relevant real-time data is the level of the (modern) Berg River dam: http://www.dwa.gov.za/Hydrology/Unverified/DetailStageFlow.aspx?Station=G1R004FW&Type=Flow&Rain=N

The last 'official' CoCT reading was 8am on Fri 15th showing 57.6%. The current reading (06:00 on Mon 18th) is 62.4%.

There was steady inflow on Sat 16th (59%, from Thursday's rain), then a huge 2% jump last night (Sun 17th), with levels likely to rise for several more days this week.

No data on other dams yet, but my guess (based on past data) is that the average rises at half of the Berg River rate, so 2-3% increase from this cold-front.

 

[Geoff.D]

At least SAWS has updated their website today with the synoptic chart now as at 06:00 today the 18th.

 

[Gordon_R]

At least SAWS has updated their website today with the synoptic chart now as at 06:00 today the 18th.

All models and charts are approximations of reality. I look at up to 800 charts per day (14 days forecasts), each have their pros and cons. Relying on only one is kinda limiting!

Rainfall is hard to measure (even with the best equipment), since it varies so much by location, and particularly elevation...

Edit: The SAWS rainfall figures for the 24 hours to 8am on Mon 18th show a rather different rainfall distribution from last week's more thundery and showery event: http://www.weathersa.co.za/media/data/climate/nr_daily_rai.pdf

Highest include Kirstenbosch 40mm, Ceres 39mm, Jonkershoek 25mm, Garbouw 23mm, etc. Most other places received much less rain, particularly away from the mountains.

Note the phenomenal orographic effect difference between the Jonkershoek Valley station, and the Dwarsberg (Jonkershoek mountain) rainfall figures!

Edit: Official dam levels up 6% to 38% during the last week! See: http://resource.capetown.gov.za/doc...ity research reports and review/damlevels.pdf

 

[Garson007]

38.1% Hectic. We should already be avoiding Day Zero next year if no more rain falls, I'd expect.

 

[Willy Strong]

This is a proper winter. Not like last year. Raining nicely in the Northern Subs.

 

[Splinter]

38.1% Hectic. We should already be avoiding Day Zero next year if no more rain falls, I'd expect.

This is a proper winter. Not like last year. Raining nicely in the Northern Subs.

Yes - but it doesn't mean we can all go full retard on water consumption now (not saying it's you chaps - just a generalization). Still need to save water.

 

[Willy Strong]

Yes - but it doesn't mean we can all go full retard on water consumption now (not saying it's you chaps - just a generalization). Still need to save water.

Agree.

 

[Tinuva]

Yeah we won't go bananas on the water, but at least its one less worry for next summer. Can use my jojos for the garden and car wash, and relax. City water will only be used for what we were allowed to use last summer.

 

[Gordon_R]

Nice to see the inflow persisting the day after the storm. Average dam levels were up an additional 1% on Mon 18th to 39% in total: http://www.capetown.gov.za/Family a...and-sanitation-services/this-weeks-dam-levels

The Berg River and Wemmershoek dams seem on track to reach 100% this winter, though they only make up 20% of the total storage capacity. The other bigger dams are Theewaterskloof and Voelvlei, though they will struggle to exceed 50-60% IMO. This will limit the overall storage to 60-70% by the end of the year (unless it is an unusually wet winter).

 

[mercurial]

Nice to see the inflow persisting the day after the storm. Average dam levels were up an additional 1% on Mon 18th to 39% in total: http://www.capetown.gov.za/Family a...and-sanitation-services/this-weeks-dam-levels

The Berg River and Wemmershoek dams seem on track to reach 100% this winter, though they only make up 20% of the total storage capacity. The other bigger dams are Theewaterskloof and Voelvlei, though they will struggle to exceed 50-60% IMO. This will limit the overall storage to 60-70% by the end of the year (unless it is an unusually wet winter).

That is remarkably better, so I'd take it!

 

[The_Right_Honourable_Brit]

When are the next big rains?

 

[Scooby_Doo]

When are the next big rains?

The windguru says this coming Monday and then again Friday.

https://www.windguru.cz/287694

 

[Gordon_R]

When are the next big rains?

The windguru says this coming Monday and then again Friday.

Long range forecasts are very fickle, but all the models indicate lower than average rainfall in the last 10 days of June.

 

[mercurial]

40% now

 

[Gordon_R]

40% now

Yes, 40% average dam levels is great!

But, you have to put it into perspective: https://showme.co.za/paarl/lifestyle/nature-outdoors/cape-water-and-dams-report-108/

How long will the water last?

A mid-month correction increases the volume of water that I now expect to flow into the dams this month to 116 M.cuM of water. This would see us reach end June with 378 M.cuM in storage.

Very satisfying, but still a long way short of the 500 M.cuM that we must reach if we are going to be able to supply agriculture with most of its normal annual allocation of 160 M.cuM of irrigation water and still have enough water left to cope with our summer residential and business demand.

Putting it into context!

As can be seen from the CoCT graph below, 2018 is starting to look like 2013, which was an average rainfall year that lifted the dam levels by some 350 M.cuM over the full winter season. If that were to happen this year then we would end winter with some 550 M.cuM of water in storage. This would be far safer than in 2017, but still too little to significantly ease water restrictions.

The fact of the matter is that while the rains have been early and strong, it is only Voelvlei and Wemmershoek dams that have received above-average rainfall to date. Rains at the other dams are on or below the past averages according to the graphs produced by UCT.

 

[Shi]

Yes, 40% average dam levels is great!

But, you have to put it into perspective: https://showme.co.za/paarl/lifestyle/nature-outdoors/cape-water-and-dams-report-108/

Should we not be concentrating more on the Western Cape dam levels (just over 31%) rather than just the ones supplying CT?

 

[Rouxenator]

Any plans for building new dams?

Had an interesting thought the other day as I drove through Du Toits kloof. If they build a dam towards the end of the kloof as you get closer to the turn off to Rawsonville it could save up quite a bit of water. There are no farms in that area so no land will have to be repossessed and there is good water flow most of the time, so a good catchment area.