Cape Water and Dams Report
(Stettynskloof Dam. Now at 95% of capacity. Photo : DWS)
Dams – Latest levels: Winelands and Cape Town
Report nr. 105 (updated 4th June 2018) on the main dams serving
Cape Town City and nearby Boland/Overberg towns
A wonderful week. As forecast, even heavier rains than in the preceding week fell in all the dam catchments raising combined water storage levels by an impressive 51.9 M.cuM (5.8%). Combined water volumes stored rose from 23.6% of capacity to 29.4%.
During the same week in 2017 the dams dropped by 2.0 M.cuM (0.3%) to 19.1% of full capacity.
May 2018 has surprised to the upside, with a solid lift to all the dam levels for what increasingly promises to be normal rainfall year bringing at least a partial recharge of all the main dams.
How long will the water last?
We still have a long way to go, but it is starting to appear that winter 2018 could see the combined level of the main dams lift into the 450-500 M.cuM range; i.e. 50%-60% of capacity or better. This is vitally important as it would permit an extra 100 M.cuM of water to be made available to agriculture in spring for irrigation to help farmers start to recover from the ravages of the past two years.
However, this would not also enable restrictions to be lifted as the water remaining for household and business use would be similar to the limited amount that was available at the end of last winter.
As expected we ended May with far more stored water (262 M.cuM) than we began the month (182 M.cuM) from a very solid net inflow of 82.1 M.cuM of water across May. I have accordingly updated the chart and added a line for July to complete the 12 month cycle.
We can now with certainty say that with this much water already stored in the dams, we will have achieved our “success target” and that ‘Day Zero’ is deferred until at least the end of winter, 2018.
(Here is our model predicting the amount of water likely to be stored in the dams by mid-year.)
Putting it into context!
To reach the combined level of 50% of capacity we need to receive at least one week of rain equal to that of last week, to fall in the catchments during each month of June, July, August and September 2018! So 4 more separate weeks, each giving us a lift of 50 M.cuM or more, with enough rain in between times to take care of our day-to-day use, is needed. We may expect this much if we enjoy a normal rainfall winter.
But in order to become relatively safe with 70%+ dam levels, we would need twice that much rain, i.e. a recharge of 100 M.cuM per month, each month through winter. That will be a tough ask.
The following CoCT chart shows the rapid lift in dam levels over the past two weeks. But it also shows that of the recent ten years only one year (2012) brought the recharge volume of 450 M.cuM that we would need to now get back to the 70% capacity level. Simply put, it argues that we have only a 1:10 chance of that much rain arriving this winter.
In reality we are still far from this goal and we should continue to maintain our reduced water usage patterns until earliest end-August by which time we should be better able to judge how the winter will turn out. It is unlikely that the authorities will relax restrictions before then.
While it is important that progress is steadily made on facilities to produce extra potable water, it is worth noting that, assuming an average of around 40 mm of rain across the entire 2000 sqKm of the Cape Town Metro area last week, the total rainwater falling to the surface would have been around 80-100 M.cuM.
In other words, water equivalent to one quarter of the whole annual unrestricted consumption of the Metro fell across the wider city in the matter of just a few days. Or; almost the equivalent of all the new fresh water that we hope the augmentation systems will one day produce annually for us, fell from the skies across the city in just two days.
This so argues for the widest possible installation of household-level rainwater capture systems. Just 500,000 homes equipped for rainfall capture and storage could reduce demand on the water supply system sufficiently, for example, for us to avoid building and operating a 100 ML/d desalination plant.
Although overall water used from all sources ticked up again this last week – possibly due to a sense of relief encouraged by all the rain – the portion of extra water produced through the augmentation initiatives also rose to 32 ML/day, an improvement of 10% over the preceding week. See our report on the status of Cape Town City’s augmentation initiatives here.
(Graph tracking overall use and production of extra water through the augmentation efforts).
How well are we actually doing?
Our position at red ‘X’ on the following graph, i.e. at nearly 30% of total storage capacity shows that net inflows have well exceeded our goals and have lifted us well away from the danger zone for now. On-going rains and surface water run-off should further boost dam levels.
(See here for a detailed explanation of how the chart is to be read).-
Will the weather help?
Good rains fell as predicted, especially in the catchments of the six main dams.
Here is the rainfall recorded at the weather stations located at the various dams for the period April 2018 to date. Particular beneficiaries have been Berg River and Wemmershoek dams, with Theewaterskloof Dam also doing especially well
What rain should we expect?
1) The weather system previously predicted for 11/12th June appears to have sped up, now promising to deliver 15-25 mm to the Voelvlei and Wemmershoek catchments on 10th June.
2) A deeper system that could strike around the 18/19th June higher up the coast from the north-west may result in another 40-80mm in all the catchments. The NOAA/CPC chart for the week after next gives a sense of where the heaviest of this rain will probably fall.
3) More rain is expected around the 26/27th June.
What are the authorities doing?
Purification and treatment (“production”) of bulk water supplied by DWS from the dams as well as from other sources is the responsibility of each municipality’s water and sanitation department. They are also responsible to deliver the water reliably to your taps and then to remove and treat your waste water and sewage before disposing of it.
Meet Dr. Gisela Kaiser, Executive Director, Informal Settlements, Water & Waste for Cape Town.
Dr Kaiser has a PhD in Construction Management in the Faculty of Engineering, the Built Environment and Information Technology, with focus on improving decision-making with regard to the economic impact of budgeting.
Dr. Kaiser and her team of engineers, administrators and field staff, numbering over 8,000 people, are dedicated to producing and getting fresh water to us wherever it is needed across the Metro and then safely treating and disposing of our waste water and sewage.
Dr Kaiser is seen here two weeks ago with colleagues sampling some of the first potable water to be produced by the new desalination plant at Strandfontein.
As reported recently in a Groundup interview by Aidan Jones, Dr Kaiser explained why it is that water tariffs must rise although the people of Cape Town are using less water per person that ever before.
1) A municipality is duty-bound to ensure that it balances its budget.
“We do not work at making a profit,” said Kaiser. “The revenue that we foresee will cover our costs to provide water and sanitation services”. The recent crisis has made it clear that water production and supply has historically tended to be underfunded.
2) A fixed charge has been proposed by the City to cover the costs of the pipe network and the new projects to increase the water supply to the city.
“The fixed cost for the whole pipe network is a lot more than the cost of the actual water that flows through it, and that’s why we had to introduce a fixed charge into the mix,” said Kaiser.
3) Reduced revenue and the increased cost of water supply infrastructure mean that the City has to raise water tariffs.
“If we used to sell 1,000 million litres [of water] a day but now we can only sell 500 million litres a day, we need to still cover the costs of the whole network,” said Dr. Kaiser. “So our costs are not a lot less than for 1,000 million litres, but our revenue is halved, so we actually have to face a doubled unit cost [for water delivered],” said Kaiser. This cost must still be covered. “And that’s really what we mean by having to increase tariffs just because our sales are down,” said Kaiser.
In a discussion with me, Dr. Kaiser pointed out that following progressive pricing principles, under the new tariffs those using up to 6000L/mth on the first step of the tariff will only be paying 80% or less of the full cost of the water whereas the price to those on the second step will be close to the full cost of the water. Regarding tariff steps 3 and 4 it is foreseen that those households will have opted to use larger volumes of water and as such will in a sense be responsible for augmentation being needed to meet their greater water demands. Therefore it is also reasonable that large volume users pay a premium to cover the higher cost of the production of water through augmentation processes.
Regarding the augmentation effort itself, according to Dr Kaiser modelling indicates that the Metro can be safely supplied currently if a supplementary water supply of 100 ML/d is provided. This would need to be expanded each year by a further 30 ML/d of capacity. So to cope with likely growth in demand for water, in addition to the dam optimisation and increase in bulk water supplies being undertaken by DWS, the Metro is embarking on a program to build 350-400 ML/day of extra water production capacity. This should be sufficient to cover its growing needs for the coming 10-15 years.
PS: on the subject of salaries for municipal staff and executives, COGTA sets the salary scales, nationally. Negotiations are in process but at way less than the 17% increases mentioned by some.
Read here about Cape Town’s reduced water and sanitation tariff increases.
Here are the levels of the six main dams serving the Cape Town/Overberg/Boland area. Combined levels rose from 23.6% to 29.4% of capacity.
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
Read about South Africa’s desalination policies and initiatives.
Click here to see Winelands Weather forecast of possible near-term rain.
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.