Cape Water and Dams Report
(Steenbras Upper Dam. Now 100% full. Photo : DWS)
Dams – Latest levels: Winelands and Cape Town
Report nr. 118 (updated 20th August 2018) on the main dams serving
Cape Town City and nearby Boland/Overberg towns
Moderate rains saw total combined levels rise by 12.0 M.cuM (1.3% of capacity). Overall water in storage climbed from 58.4% of capacity to 59.8%.
During same time last year, levels rose by a very similar 12.5 M.cuM (1.4%) to 32.1% of capacity.
60% of capacity; well, that is our initial target ‘done and dusted’. What a very different picture compared to the 32% level that the dams had achieved by the same point in 2017.
What the above graph shows however, is that except for late May and the month of June, a 7-week period which brought exceptional rains, much of July and August so far have seen below average rainfall mostly similar to that which we received during the same weeks in 2017. It will be a shame if recharging of the dams stalls near this level.
My dam level prediction model seems to be tracking events quite well, with the late rains expected at August month-end likely to lift the combined storage up into that 545-550 M.cuM range.
The long-range forecasts do show rainfall systems striking us during early September, so winter is by no means over yet. But for now, it seems unlikely that we will get much beyond 65% of capacity of water stored in the main dams by end of October.
However, I hope that the level of water finally stored by end-winter will be sufficient for DWS adequately supply agriculture while also rolling back restrictions to level-5 and increase water allowances to, say, 75L/p/day
(Here is our model predicting the amount of water likely to be stored in the dams each month)
Putting it into context!
Let us take a look at the individual dams too see the extent to which they have been recharged by recent rains (in all cases the black line is this year’s outcome).
Berg River Dam.
Capacity 127 M.cuM.
Now 89.8% full.
As this dam is in danger of overflowing still this winter, water is being pumped from BR Dam to TWK Dam at a rate of some 2 M.cuM/wk.
Steenbras Lower Dam
Capacity 33.9 M.cuM
Now at 66.9% of capacity.
Steenbras lower Dam is coupled with Steenbras Upper Dam. The upper dam’s overflow is the main source of water for the lower dam.
Steenbras Upper Dam
Capacity 31.8 M.cuM.
Now 102.3% full.
Steenbras Upper Dam receives the bulk of the inflows. Water sent to the lower dam through turbines makes electricity for Cape Town.
Theewaterskloof Dam.
Capacity 479.4 M.cuM.
Now 43.9% full.
This huge dam which holds 55% of the stored water in SW Cape will take several years of normal rainfall to fill. It also receives surplus water Now pumped from BR Dam.
Voelvlei Dam.
Capacity 158.6 M.cuM.
Now 68.9% full.
The primary reservoir serving the Swartland and West Coast towns. A plan is underway to also allow surplus water from the Berg River to in future be pumped up to VV Dam.
Wemmershoek Dam.
Capacity 58.7 M.cuM
Now 83.6% full.
Along with the BR Dam, WHK Dam enjoys the strongest and most reliable rainfall. This dam is owned by Cape Town.
Augmented water supplies i.e. the difference between the water drawn from the six main dams (478 ML/day) and that consumed from all sources (527 M.cuM) this week stood at 49 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 further improvement last week.
The two large inland irrigation dams, Brandvlei and Kwaggaskloof now both stand at 41% of capacity. Clanwilliam Dam is full and spilling and the lower smaller Bullshoek dam stands at 93%.
Will the weather help?
Weather systems during August have delivered only relatively light and scattered rain. The problem has remained that the high pressure over the land has conspired to deflect most of the on-coming rain out over the ocean.
Our chart of rainfall at the dams shows that, except for Steenbras and Wemmershoek which have received reasonable rain, the others dams remain woefully behind the averages. Hopefully this will improve next weekend (see below what we may expect).
Click here to see ShowMe Winelands Weather forecast of possible near-term rain.
What rain ought we to now expect?
1) The next main bout of rain is due between 25th and 27th August. All the catchments are forecast to receive good rain across three days. Rainfall is expected to range from 30-40 mm in the west to 70 mm for TWK and 70-80 mm for Wemmershoek.
This forecast chart shows a solid band of rain settling across the entire SW Cape as the high pressure over the land recedes.
2) A second band of rain is forecast to move in between 30th August and 2nd September, bringing a further 10-30 mm of rain to the catchments.
3) Looking further out, another spell of rain is expected at the end of September.
El Nino is now starting to emerge strongly. This graphic shows two ENSO zones:
– zone 4 is the west Pacific area where the warmer water first manifests. It shows a rapid rise in temperature. The warm water then usually spreads to the east.
– zone 3.4 is the Pacific Ocean mid-section where the El Nino state is measured; it seems that this area will move into El Nino temperature range within a few months.
We need to be concerned about this for two reasons:
1) A full El Nino condition usually signals a dry period for the inland areas of South Africa. Given the problems currently being experienced with the fresh water supplies inland, the return of a drought may make matters worse up there and later knock-on to the SW Cape.
2) El Nino does not necessarily have a direct effect on SW Cape weather, but typically it will tend to bring more settled inland weather and help build stable high pressure blocking systems, deflecting on-coming low pressure systems away from the land. If El Nino builds quickly it might bring our southern winter to a premature end.
What are the authorities doing?
There is nothing new to report this week.
What is the citizenry up to?
Dr. Anthony Turton in conjunction with the not-for-profit entity, Water Shortage South Africa, has over the past week appeared several times on various TV shows and stations highlighting concerns about the deteriorating situation with the inland river systems.
The strategy is that once general awareness of the key problems has been established, specific actions will then be commenced through the courts seeking, on one hand, to unlock the powers of DWS to enforce water management compliance by local authorities, and on the other hand, to charge officials who have failed dismally in their responsibility to deliver fresh water systems.
Read more about this “Water Lions” initiative at https://www.watershortagesa.com/
Watch Dr. Turton being interviewed on SABC Focus and read about the problem in more detail at https://www.thesouthafrican.com/dr-anthony-turton-vaal-river-fix-r800bn-r1tn/
If you wish to contribute to this cause, visit https://www.watershortagesa.com/donatewaterlion
What is happening elsewhere?
Having been in Europe for several weeks I have been intrigued to see how much attention is being given by various media channels to the growing climatic challenges. Every day there are articles and discussions trying to establish what the problems may actually be and what impact these could in turn have on the populations in the near future.
While water shortages are less of a problem, due to record high temperatures both Europe and USA are being beset by runaway fires (amazingly, in the period May, June, July 2018, every weather station in the whole continental USA recorded record high temperatures for that time of year).
In the east, countries ranging from India to Japan, have experienced massive floods.
We are certainly not alone in having growing climatic issues with which to grapple.
Summary: Combined levels of the six main reservoirs serving the Cape Town/Overberg/Boland area rose from 58.4% to 59.8% of capacity. Widespread rain is expected at the last week of August.
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 here about Cape Town’s reduced water and sanitation tariff increases.
Plan ahead for possible water outages; here are points that could help you.
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.
Views expressed in this article, and comments in response, are those of the writer and commenters alone and do not necessarily reflect the views and opinions of ShowMe, nor is any warranty hereby given as to suitability for any purpose of a reviewed enterprise or as to the quality of offered advice, products, services or value. Copyright ShowMe Paarl. All rights reserved. Copy only with prior permission.