Dams – Latest levels: Winelands and Cape Town
Latest report (updated 21st February 2017) on the main dams serving
Cape Town City and nearby Boland/Overberg towns
Combined water stored in the six main Cape dams fell to 34.0% of overall capacity (down from 35.7% last week).
According to DWS figures published today, net outflows from the six main dams during this past week increased to 15.5 Million cuM vs the prior week’s reported net outflow of 10.4 Million cuM.
Initially, this implies a substantial increase in consumption. However, we did mention last week that we felt the figures for the one dam were incorrect which may distort the week on week result. Thus if we add the changes registered for last week and the week prior and average them then the net outflow is around 13McuM which seems more realistic. No doubt the dam levels did decline but we will not draw any conclusions for this week. Hopefully any data error will be eliminated next week.
Given the rising media coverage and news releases by the authorities, it is hoped that awareness of the grave situation has permeated all areas and got through to most of the people. The continued reduction being achieved demonstrates widespread savings in all sectors.
For your information: our focus is on the entire SW Cape “south of the mountains” as all towns in that area draw from the same system connecting the 6 main dams and various smaller dams. Although Cape Town is the largest single user, there are many other towns and communities involved. Also there is some 15,000 Ha of agriculture that receives irrigation water from the system.
Over the past three and a half months since 1st November we have together used 37.8 McuM less water than in the same period a year ago. This has extended the water supply by some three weeks, helping to maintain supply until rains arrive.
What are the authorities doing?
Western Cape Premier, Helen Zille, in her recent State of the Province address emphasised steps being taken to make the SW Cape more drought-resilient as we reported last week here.
CTC Mayor, Patricia De Lille, has personally been calling on high volume water users and the City intends to name and shame all users convicted of over-use and/or are fined for ignoring the water restrictions. There are reportedly some 20,000 users who are consuming over 50,000 litres of water per month and who are being identified for investigation from their water accounts.
If uncertain, read here about the current level-3B restrictions and what it may mean for you.
The City has also reported that, where technically possible it is starting to reduce water pressure. This could show up at your taps as slower running water. However, there are reportedly no plans to stop water supplies completely (“water shedding”); experience shows that this tends to damage the infrastructure and cause yet more leaks when water flow is restored.
How long will the water currently stored in the six main dams last? Worst case, if the latest usage rate is taken then approximately 103 days until early June; but hopefully to mid-June.
Will the weather help? The near-term forecast shows that the SW Cape is living up to its reputation for hot, bright, dry weather through until early April. A burst of rain is now predicted for around mid-March but this is unlikely to bring short-term relief.
The long-range forecast for April is starting to show unstable, gusty weather around 6/7th and again on 24/25th April with the possibility of useful rain on both dates. And for May, rainy spells are being predicted but that is what one would expect on average and much can change in the meantime.
Your comments and concerns.
The question is often asked why more has not been done sooner to deal with the potential water shortage? There are many possible answers to that and not all straight-forward, so I thought that it might be useful to step back from the immediate crisis and to look at one major long-term issue which authorities all over he world have been tending to underestimate.
Obviously demand is growing, but the fact is that we do have enough storage capacity in our dams provided that rains fall regularly in the right catchment areas. Our existing dams can provide for 2 years of water consumption.
So what is going on – why are we short of water? The fundamental problem is that rainfall patterns have changed and the traditional rains have started to fail. Many have noticed that, year after year, the rains seem to have been gradually drifting out to later in the winter and that when it does rain, the storms and showers seem to be more intense. In the process, those good old Cape rainy spells where it drizzled for days on end don’t seem to happen any more.
And what is the reason for this? Climate Change! Something that is hard to measure and pin down.
The supporting facts:
It is today a globally recognised truth that the earth’s climate is changing . The consequence for the Western Cape is that our winter rainfall zone is likely to experience gradually declining average rainfalls, rising average temperatures and stronger, longer-prevailing south-easterly winds. And the rains that do fall will tend to come later in the season, out as far as November.
Average temperatures in the coastal zone are expected to rise by 1.5 to 2 degC by year 2050 and by 3 to 4 degC by the year 2100. The area will become drier in the west and perhaps rainier in the east.
The main local outcome seems to be that, instead of shifting northwards in winter as they used to do, the South Atlantic high pressure zones may stay further south in winter (much as they do in summer). Accordingly the winter storm tracks appear to be shifting southwards away from land so the traditional and vital heavy winter (June-August) rains could become less dependable; perhaps more often falling uselessly out over the sea.
The probable consequences and challenges:
The predicted weather outcomes are less frequent and shorter-lived winter snows; reduced effective rainfall and surface water run-off; higher evaporation from soils and from the dams; slower recharge of underground water; more frequent wild fires. And when they do come, rains are expected to be more intense with periodic flooding.
Related risks are that rising sea levels and storm surges may endanger coastal residential areas. River estuaries will become vulnerable and low-lying waste-water processing and disposal facilities may sustain periodic damage.
Tellingly, since 1985, in SW Cape the winter rainfall of one year out of every three has been below 70% of the long-term average. This indicates that the main dams could in future regularly struggle to recover from droughts as has happened a number of times over the past three decades. The higher temperatures and lower rainfall would also place many food producers under pressure and further increase demand for irrigation water, thereby increasing competition with households for adequate water supplies.
Economically, all this could force major adjustments in the agricultural sector on which the Cape and its inhabitants depend for many jobs and much of its income.
Couple all this with the steadily growing local population and influx of people from other parts of the country and it becomes clear that water shortages and water restrictions could well become a standard feature of local SW Cape life.
The climate changes outlined above are global in their nature and the SW Cape cannot avoid their effects. That says then that the people living in the SW Cape must also be prepared to change their behaviour to deal with their irrecoverably changed environment.
What then to do?
1. Given the likely permanence of this climate change, doing nothing is not an option. Time is running out. Politicians and planners must accept the challenge and commence implementing ways to improve water capture and utilisation as soon as is practical.
2. All water users need to reduce consumption and continue to save water to some extent.
3. Households must be drawn in to creating the solution. This is not someone else’s problem, it is all our problem. Wherever possible rainfall capture systems from roofs to tanks should be installed, supplemented by shallow wells. Perhaps mandatory for new builds. Consider subsidisation.
4. Water re-use in all forms must be encouraged and planned. This includes ‘grey water’, recycled waste water and capturing storm water perhaps to refill the underground aquifers.
5. Draw sustainably on the Cape underground aquifers, particularly as a resource to be mobilised in years when rainfall is particularly poor and dam levels become exceptionally low.
6. Where dam walls can be raised economically on independent river systems then this should be done to increase total storage, e.g. Voèlvlei, Steenbras, and Lourens, so that we capture all the possible rain run-off. Reduce alien growth, pollution and degradation of rivers and dam catchments.
7. Ultimately install modular desalination facilities to produce more fresh water.
As one reads down this list, capital investment costs, time to implement and on-going operating costs rise sharply, step by step. So we might as well start with the “low-hanging fruit”; steps 3 – 5 could be implemented right away, both on existing properties and new builds, on a phased program while the capital intensive major works follow in due course.
How far will that take us?
When all is implemented, probably out to 2050 with a 50% increased population.
But can more time be wasted before urgently implementing these solutions? Not really.
As we stand right now, studies indicate that total surface water (rainfall run-off into existing storage) will be exceeded by demand by the year 2020. However, if we get moving right away on steps 2-5 we could be a long way down the road by 2020 with reduced demand, improved re-use and local storage extending the life of the main dams from two years supply out towards three years, making the area far more drought-resilient, with additional variable backup from the aquifers; our “underground dams”.
The current Cape Government planning document can be read here.
In Summary: outflows exceeded inflows over the week – stored water volume fell from 35.7% to 34.0% of capacity. The water usage rate apparently rose again but a possible error in the figures casts doubt.
Here are the levels of the six main dams that serve the Cape Town/Overberg/Boland area. Also shown is the total water storage level of all the dams in the whole greater Western Cape.
Read about South Africa’s desalination policies and initiatives.
Read new level-3B water restrictions here.
Read about a D-i-Y household rainwater harvesting and storage system here
Read our water-wise landscaping and water-wise gardening suggestions.
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).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.