Cape Dams Levels – weekly report (003)

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Cape Dams Levels – weekly report nr. 003

as at 12th November 2018

Wemmershoek Dam photo Oct16                                                         [Wemmershoek Dam, 90.2% full. Photo: DWS]

 

The levels of the six main SW Cape dams, as reported by DWS for the week, showed a smaller net outflow of 6.1 M.cuM and total volume of water stored fell to 648.8 M.cuM; i.e.  from 73.6% to 72.9% of overall capacity.

During the same week in 2017 the total volume stored fell by 8.7 M.cuM (0.9%)

2018-11-12A week ago the Metro was still drawing heavily from the Steenbras dams but that that has reportedly changed and water is currently also being drawn from Voelvlei Dam. The Berg River and Theewaterskloof dams should now start to reflect the effect of outflows to agriculture.

The following chart shows the weekly change in the total amount of water stored. Note that I have changed the colour coding in order to make it easier to follow present changes [2017/18 is now shown in green and current 2018/9 is now shown in red, emerging left].

2018-11-12.3                                                    [click on the graph to see an enlarged version]
 

I expect that the red line will tend to follow the general shape of the green and black lines for the coming three months, probably lying somewhat between the two and more towards the black line (which denotes 2016) due to the latest easing of restrictions. In both instances supplies of water to the irrigation boards had commenced by this stage. It is likely that around end of January 2019 that they will diverge more sharply as distribution of water to agriculture continues in 2019, whereas it was cut off during February 2017, as the green graph clearly shows.

 

It is expected that agreement on water allocations will be reached and announced by DWS this coming week.  There will be no gazetting needed as an emergency condition no longer applies.

Once DWS has set water allocations for the irrigation boards and municipalities, the latter will then decide and announce appropriate levels of restriction to be applied to their communities in order to conform with the allocations, and publish the changed tariffs.

 

The weather is quickly taking on the normal summer pattern with the dominant high pressure zone statically positioned over the Cape. No significant rain is forecast until next week when light rain will brush the southernmost Cape, perhaps bringing small inflows to the Steenbras dams. Beyond that there is some promise of thundery weather around 5th/6th December that may see 20-30mm of rain falling if one finds oneself under the storm.

El Nino is continuing to move into place but is not fully there yet – it needs two more months of above-average sea temperatures to become classified as a fully-fledged El Nino condition.

 

The Cape Metro has just released this revised drought monitoring chart which clearly shows the “safe zone” extent to which stored water could be drawn down across the summer season. This too shows that under the worst circumstances the low point of storage of some 300 M.cuM could be reached at around May 2019. This would be a comfortable situation with adequate reserves.

2018-11-12.5

 

Against this background, a number of readers have expressed concern about the possible ill-effects should current restrictions be eased.

While this is a natural response after the stresses of the past few years, I feel that I must reiterate that we do have considerable stores of water and it needs to be used. An appropriate outcome is that water should be used steadily across summer so that by following winter there is space for fresh rainfall to recharge the dams back up to a good level (ideally 80% or better), as has often happened before. This will still leave a good reserve in case the following rains are less strong. The fall-back would be to reimpose restrictions if the following rains fail altogether.

Because if we do not use the water, then tariffs will be forced to remain too high and cause unnecessary hardship. Furthermore, good following rains would cause the then over-full dams to spill and that new water would flow to the sea and be completely wasted.

So we should use but certainly not abuse our water. However, maintaining maximum restrictions is not the correct answer. This past drought is likely to be the worst that will happen in our lifetimes. It would be irrational to impose an unnecessarily harsh lifestyle based on an exceptional event that is unlikely to recur.

 

To remain fully informed you may like to check the following items weekly
  • City of Cape Town weekly “Water Dashboard“, to be found here.
  • Our 7-day & 24-hour weather report here shows probable rain in Boland dam catchments.
  • SA Weather Services current Synoptic Chart here showing the currently developing weather.
  • Look at our supporting current monthly report here.

 

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.

 



Looking hopeful, but early days yet.

The latest data point on the cumulative storage for Cape Town dams shows that inflows are now tracking the median value for the last 70 years.  If the rains pick up even more, we could start beating the average, which is vital if we want make up the shortfall created by the last few years.  If it falls back, then it is even more critical that we maintain a conservative approach to water usage well into next winter.

The key is not to get complacent.

Cape Town households use less than 6000 litres pm

stock-photo-tap rev1

Over 200,000 Cape Town households use less than 6000 litres/month

(Repeated from Cape Town City media release) 29th May 2018

 

The monthly update of the water map for April shows that 211 000 households have achieved the dark green water-saving dot for their water saving efforts. This marks a slight decrease but it is heartening to see that a large number of households are still going green.

 

The dark green dot for water saving is awarded to households who are using 6 000 litres or less per month.

Water map data since December 2017 shows the following trend:

Month

Number of dark green dots

December

150 000

January

154 000

February

203 000

March

219 000

April

211 000

 

Visit www.capetown.gov.za/watermap to view the latest map.

 

Consumption is indicated on the map as follows:

  • Dark green dot: household using less than 6 000 litres per month
  • Light green dot: household using between 6 000 and 10 500 litres per month
  • Grey dot with small dark green centre: estimated water meter reading of less than 6 000 litres per month
  • Grey dot with small light green centre: estimated water meter reading of less than 10 500 litres per month
  • Solid grey dot: excluded property (including: sectional title property or group housing / undeveloped property / water use is zero / no available information for the property / estimated water meter reading of more than 10 500 litres per month)

 

Please note: The map simply indicates water consumption for free-standing houses, not compliance with water restriction limits. Households with higher consumption may have many people living on the property, or may have an undetected water leak.

The map shows consumption information from meters read in the previous month, and may include a portion of consumption from the preceding month. This information is updated from the third week of the following month.

Households using more than 10 500 litres per month are not shown on the map. Remember that consumption higher than 10 500 litres per month (no green dot) does not necessarily indicate water abuse.



Water situation – statement by Mmusi Maimani

de-villiers-dam-table-mountain-coct

Date: February 6, 2018 | Posted in News | Plettenberg Bay News

 

Statement by DA Leader, Mmusi Maimani

Saving water is still the only way to defeat Day Zero

Day Zero is being progressively pushed back, but it is still a very real and present threat. All residents must keep within the 50 litre per day limit, which was the main message in my newsletter last week.

Thanks to a decline in agricultural usage, Day Zero has been pushed back to 11 May this week, from 16 April last week. And we can push this back still further in the coming weeks, through a combination of using less water and producing more water.

This has to be a team effort. We’ll only defeat Day Zero if we all pull together.

Using less water

Daily usage by the City of Cape Town is steadily coming down but at 547 million litres used per day, it is still far above our target of 450 million litres per day.

The city is reducing demand in two main ways.

  1. First, by implementing a stricter water restriction and tariff structure, which came into effect on 1 February restricting usage to 50 litres or less per person per day. The City is continuing with the mass roll out of water management devices at high consumption households. Over 30 thousand of these have been installed since 1 October 2017.
  2. And second, by reducing water pressure (“throttling”). It is not possible to water shed a specific area, like you would load shed electricity. The pipe system is a complex one, making it difficult to isolate specific areas. And letting the pipes run dry risks bursting them once water is returned to them. Even pressure reduction is a complex process. But the throttling will continue to intensify, meaning households will experience a noticeable drop in pressure and those in high-lying areas and in apartment blocks may be without water altogether for a period of no longer than 12 hours at a time. Nonetheless, an accelerated programme of pressure reduction valve installations has been in effect since last month, which allows the City’s engineers greater control over pressure. Not only does pressure management lower consumption by reducing the rate at which water flows to properties, it also reduces loss from leaks and pipe bursts.

In responding to droughts, demand management through restrictions and pressure reduction is recognized as international best practice. There was simply no way the City could have predicted the severity of this drought and been able to sustain ordinary supply levels to residents three years into the worst drought in history.

Producing more water

While expecting residents to do everything possible to use less water, it is also entirely fair that residents expect the City to do everything possible to produce more water.

For the next 60 days, an additional 67 million litres a day will be added to the system, transferred from the Palmiet-Kogelberg dam, which has had plentiful rainfall and is full. This has been a collaborative effort between the City and the farming community of the Elgin-Grabouw valley, to whom we are extraordinarily grateful.

Groundwater extraction from the Atlantis Aquifer has been supplying about 12 million litres per day for the past week, and we expect this to increase to around 30 million litres per day over the period 2018 to 2020 once the project is complete. Likewise, boreholes being drilled into the Cape Flats Aquifer should start adding a further 80 million litres per day and those into the Table Mountain Aquifer roughly 40 million litres per day from June, over the period 2018 to 2020. The City recognizes that groundwater extraction must be approached with great sensitivity, as aquifer water is a finite resource. The City intends to allow the natural recharge of aquifers in the medium term and ensure that any long term extraction is conducted sustainably.

Three temporary desalination plants are coming online soon. The Strandfontein plant is expected to produce a total of 7 million litres per day once it is fully up and running, with 2 million litres per day from March and the additional 5 million litres per day coming online in May. The V&A Waterfront plant is expected to start producing an additional 2 million litres from March. And the plant at Monwabisi is expected to provide 2 million litres per day from April and will be providing 7 million litres per day by May, once it is at full capacity.

Legal responsibilities

These projects appear to imply that it is the City’s legal responsibility to provide bulk water. It is not. Almost everything the City and Western Cape Province are currently doing to augment water supplies is technically outside their legal mandate.

The budget and responsibility for bulk water supply and storage resides 100% with the national Department of Water and Sanitation (DWS). Section 3 of the National Water Act states:

(1) As the public trustee of the nation’s water resources, the National Government, acting through the Minister, must ensure that water is protected, used, developed, conserved, managed and controlled in a sustainable and equitable manner, for the benefit of all persons, and in accordance with its constitutional mandate.

(2) Without limiting sub-section (1), the Minister is ultimately responsible to ensure that water is allocated equitably and used beneficially in the public interest, while promoting environmental values.

(3) The National Government, acting through the Minister, as the power to regulate the use, flow and control of all water in the Republic.

DWS’s infrastructural budget for the year 2017/18 was R12.2 billion. The DWS has only spent R5 million of this in the Western Cape over the past 3 financial years – on clearing a build-up of silt in the Voelvlei Dam Catchment Area, a project they failed to complete. (The Western Cape government, using budget that was not technically available for that purpose, completed the work of cleaning the water canals.)

Local municipalities are responsible for delivering water from dams to households, with as little wastage as possible. This year, the City of Cape Town has further reduced the volume of water lost to leaks, theft and faulty meters. Our average loss rate is 16% against a national average of 36%.

It is vitally important that South Africans understand the legal distribution of responsibilities, because most of the country faces water shortages in the very near future. Water is already running out in parts of Eastern Cape, KZN, Free State and Limpopo. Lesotho’s dams, which feed parts of the interior, are very low. Many smaller towns have experienced periods of dry taps in the recent past. Last week, the DWS confessed that the taps may run dry across the country within the next few years.

Many more cities will soon be staring down the barrel of a Day Zero gun. We cannot lurch from one local water crisis to the next blaming local and provincial governments each time. And it is reckless for anyone to drive the false narrative that they are responsible.

Blaming local and provincial authorities for water shortages in 2018 is like blaming them for load shedding in 2008. It’s simply irrational. But worse than that, it lets National Government off the hook at a time when we need to be holding them accountable like never before.

If anything good has come out of the Cape drought crisis, it is the loud and clear message that water is the lifeblood of our economy and society. With the realities of rapid population growth, urban migration and climate disruption, we must put water planning and management centre stage. And we must all start treating it as the precious resource it is.

Thank you to all those Day Zero heroes who are already doing so!

Mmusi Maimane DA Leader




Day Zero Date – a basis of calculation.

Calculation of likely Day Zero date

Using current and likely future water consumption patterns, projected as at end-February 2018.

2018-02-26-5

 

I comprehend the gradually changing water consumption patterns in my model and therefore my predictions of steadily falling weekly water consumption results in the dotted black line curving away to the right and indicating a “Day Zero” date falling around 30th June at point ‘Y’, depending upon how well households further reduce their water consumption over the coming 4-5 months.

 

Going through it step-by-step.

Starting from the 37.5% total storage at beginning November 2017, the business-as-usual consumption expectation indicated a sharply descending fall in dam levels, originally predicting Day Zero as being during week of 13th February 2018 when total storage would drop to the 13.5% level set by CoCT; that point when they would move to stage-2 of the disaster plan.

Then in November 2017 we enjoyed unseasonal rain in the catchments that lifted dam levels and effectively moved the predicted Day Zero out by two weeks to the last week of February.

My information at that time was that the so-called 10% of ‘inaccessible water’ in the dams was in no ways definite and that if necessary, given some extra filtration, more of that last ‘dead water’ could be accessed. In fact, the dams could be drawn down to virtually zero but not easily in all cases. So I assumed that they would be pulled down to, say, 7.5% (line “D”) thereby making more available for consumption. That in turn allowed a corresponding drop in the Day Zero trigger level from 13.5% to 11% of capacity (line “B”) while still retaining the same stage-2 reserve of 3.5% of capacity “E”). This pushed the point where line “A,B” intersects the 11% line out into March. [In the meantime DWS has announced that they are preparing to pull both Voelvlei and Theewaterskloof dams down to zero if necessary. That would make yet more water available.]

The next major change in November was when DWS imposed new limits and cut agricultural water allocations to just 40% of normal. The effect of this massive reduction in overall water consumption is reflected by the blue-striped zone, labelled “F”the current position being where the actual consumption (denoted by the red ‘X’) now lies. Without further savings then the theoretical Day Zero date would be around end-May 2018, on the disaster stage-2 line (point “G”); by then dam levels could have dropped to 11.0% of capacity.

Although they have been drawing their water allocation fast, in fact agriculture has rapidly reached the 40% limit and the irrigation flows were largely cut off by end-January with most of the rest reaching the limit and closing by end-February. The net effect will be that the agricultural sacrifice has extended the communally available water supply out to late May (point “G”). At that stage agriculture’s contribution should be exhausted and “Day Zero” will have arrived for all the farms.

In February 2018 it was announced that the Groenland Water Users Association (Elgin/Grabou) would release their surplus stored water to be pumped through to Steenbras dam. This donation is expected to add 8-10 M.cuM of water to the SW Cape water supplies and help us to reach a point half way between “G” and “I”.

Now, although rain should start by June this is still too tight and the business and household users in the metro and municipalities must save stringently and meet their reduced allocations. In January the CoCT was running at about 586ML/d but has subsequently dropped down to the current level of 510-520 ML/d.

From 1st February level-6B restrictions require consumers to further reduce to 50L/person/day. Residents now must cut usage in order to save that blue zone labelled “H”. This action would make all the difference and enable us to reach “Success Day”, defined as arriving at 30th June 2018 with 100 M.cuM of fresh water still stored in the dams (point “Y”). Average consumption is still up in the area of 75L/p/d  and every effort must be made to encourage that half of the population that is still using too much water to stop doing so (hopefully the new harsh tariffs will help).

As I write, the point red “X” lies at 23.7% of capacity on 26th February – the small yellow circles with ‘x’ mark the previous positions of “X” over the immediate past. Graphically the task is to make sure that, as position red “X” moves along,  it stays on or to the right of the dotted black line, which will show that we are achieving or doing better than our weekly consumption target. At the moment we are doing very well due to the water being donated from the Palmiet system.

If we do reach mid-year with sufficient water in the dams, then nature should start to help with winter rains and low evaporation commencing late-May, but surely in June (yellow zone “I”).

Last but not least, various augmentation initiatives should be starting to make steadily growing contributions (brown striped zone “J”) and, in the final analysis Cape Town should just skim past the lowest point and out of immediate danger. In fact, hopefully the total available water will recover along the heavy dotted red line as the dams recharge, labelled “K”.

In summary, this outcome depends clearly on three main things:

1) the dams will be drawn down at least into the range of 6% – 7.5% of capacity if needed!

2) agriculture is exhausted, so businesses & households must now reduce consumption to 50L/p/d.

3) at least normal rains needs to arrive to start recharging the dams from July onward.

If rains once more fail and Day Zero arrives, then we will at least know we have done our best!

 

Tom Brown,

retired international businessman and fruit farmer in the Klein Karoo.

26th February, 2018.