Dams – Latest levels: Winelands and Cape Town
Latest report (updated 18h September 2017) on the main dams serving
Cape Town City and nearby Boland/Overberg towns
Last week inflows barely exceeded outflows, with combined water stored rising by a mere 3.0 M.cuM (0.3% of capacity) vs 18.5 M.cuM (2.1% capacity) during the prior week. Total stored water rose slightly to 37.1% of full capacity (vs 36.8% the previous week).
During this week in 2016 combined level of the dams rose by 7.9 M.cuM to reach 61.1% of capacity.
[Why since 1st November 2016? that was when harsher level 3 restrictions were imposed].
Current status?
The dams now contain 330 M.cuM (245 M.cuM of easily accessible) water (last year this stood at 544 and 459 M.cuM respectively).
The only high point this last week was the 24 mm of rain recorded at Dwarsberg which gave Berg River Dam a useful boost. No meaningful rain fell in any other catchments so the other main dams relied on run-off from previous week’s rains for the slight lift improvement.
How long will the remaining fresh water last?
Here is our progressive estimate for 2017 compared with what actually happened in 2016.
Starting with 309 M.cuM total stored water on 3rd September, the model recalculated that we would stand at 325 M.cuM of water stored by 3rd October. Month-to-date rainfall in September has been slightly better than last year so the projection could well improve by end-September.
Nevertheless, if not much more rain falls in the catchments, the City of Cape Town will be totally reliant on planned interventions (desalination and groundwater abstraction) to start producing high volumes of fresh water by end of 2017 otherwise all easily accessible water in the main dams may be exhausted by 3rd week of February, 2018.
What ought households to be doing?
Plainly, the risk is that water consumption targets may be cut further at some point. All households need to consider ways in which they can further reduce water usage if required.
If you haven’t done so already, do calculate present water usage using the handy calculator on the Cape Town City website here. Examine the results and consider how some of that water can be re-used to replace fresh water; e.g. re-use shower water to fill toilet cisterns or for the laundry first wash. A worthwhile goal to aim at is to reduce water consumption to below 50L/day per person in the household. Read our suggestions on ways to save water; It is not easy but it can be done – many people are achieving this and better.
Ilse van D recently reported: So proud of our family this month! We got it down to an average of 47 litres pp per day (without a rainwater tank!).
Install some means to harvest and store water under your direct control. Don’t wait – set up whatever system you can afford and then use it and practice harvesting and storing rainwater.
The City asks that households make adjustments to stopcocks to reduce the pressure of water reaching the home as a means to further save water. They advise to do it as follows (this should ideally be done during the day when the supply pressure levels are normal):
- Close the stopcock by turning it in a clockwise direction, and open it again (about a half turn)
- Go to the tap furthest away from the stopcock (this could be inside the house, in the back garden/yard or in an upstairs bathroom)
- Open the cold water tap and see if there is sufficient water flowing
- If required, adjust the stopcock a half turn at a time until a reasonable but reduced flow rate of water to the furthest cold water tap is achieved
For a video illustrating how to adjust a stopcock, please watch this video clip.
What are the authorities doing now?
City of Cape Town has announced that “The City of Cape Town’s Mayoral Committee has approved the creation of 43 temporary and eight permanent positions to ensure a timeous roll-out of the City’s emergency water augmentation projects. The approval of new positions aims to address the staff requirements for water resilience projects such as desalination (marine-, barge- and land-based), water reclamation, spring water and aquifer extraction.”
These jobs seem closely aligned to the main planned interventions and will surely be needed to manage those new and novel processes.
The City also advised that “In terms of the roll-out the City’s emergency water augmentation projects, approximately 20 tenders will be finalised and issued for the various required schemes over the next few weeks and months.” Once these tenders are awarded some idea will be obtained as to what results may be expected and by when regarding the production of additional potable water.
The City has stated that it will be further engaging with visitors to our city during the tourism season in order to encourage them to use water sparingly during this drought crisis.
The City of Cape Town has now installed 71 water management devices at private properties where excessive users of water have failed to adhere to water restrictions or to justify their high usage.
Further afield, farmers have now been advised that, in the light of the low levels of water in the irrigation supply dams, agricultural water allocations have been cut severely; in one instance by 47%. This necessary reduction in water allocations will unquestionably result in enforced drops in production with an associated fall in employment, incomes, investments and, starting already in October, lead to considerable hardship in the rural communities of the South Western Cape.
Will the weather help?
Last week some 24 mm of rain fell in the Dwarsberg area benefiting the Theewaters and Berg River dams. The other main dams received little or no rain in their catchments.
As can be seen from this forecast chart, some 10 mm of rain is still expected on 25th September.
Another 5-10mm is likely on September 29th.
Long-range forecasts presently indicate only occasional rain during October and November.
At this time of year the likelihood of rain naturally starts to diminish from occurring once every 5-7 days down to only once in 10-14 days. At the same time intensity of the showers tends to decrease.
NOAA/CPC advises equatorial sea surface temperatures have dropped into ‘La Niña’ range of -0.5 degC below average in the central and eastern Pacific Ocean.
Will this make a difference? Apparently the ‘ENSO’ forecast consensus has become that “there is an increasing chance (rated 55%-60%) of La Niña occurring during the Southern Hemisphere spring and summer 2017-18.” This promises good summer rains for the inland areas but may also cause some unstable spring weather with the possibility of some unexpected rainy spells in October-November in SW Cape.
The chart below shows the rain that has actually fallen over the dams since the 2017 winter began. Last week the rains were concentrated mainly in the area of the Berg River Dam. At the moment the outlook seems to be for average rainfall, at best, for September. This will not have any appreciable effect on the levels of the main dams and the combined level will remain critical.
In Summary: scattered rains caused small net inflows of 3.0 M.cuM. Dam levels lifted from 36.8% to 37.1% of total capacity. We are rapidly approaching the end of the traditionally Cape rainy period. Rainfall has been way less than we needed. The SW Cape is potentially in serious trouble!
This table shows the levels of the six main dams that serve the Cape Town/Overberg/Boland area as reported by Dept Water and Sanitation. It also shows total water storage levels of all dams in the greater Western Cape area. It can be seen that only the Berg River Dam managed any worthwhile increase while the Upper Steenbras dam spilled into its lower companion.
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.
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