Dams – Latest levels: Winelands and Cape Town
Latest report (updated 3 April 2017) on the main dams serving
Cape Town City and nearby Boland/Overberg towns
Water stored in the six main Cape dams fell more quickly to 25.3% of overall capacity (down from 26.8% last week). Reducing this stored volume by 89 McuM (10% of full capacity) for water that is impractical to extract, this means that only some 136 Million cuM of accessible fresh water remain.
Unfortunately net outflows from the six main dams last week, as reported by DWS, was 13.3 M.cuM; back up to the recent level. We suspect that the level recorded for the Wemmershoek dam in the previous week was not entirely accurate, leading to last week’s apparently very good result.
If this current consumption rate holds, then we are back on the previous trend line and the presently stored water will only last for around 72 days, i.e. just over 10 weeks through to the first week of June; a steadily growing risk.
One hope is that demand for irrigation water from the agricultural sector should start to diminish as the summer harvest season comes to an end.
What are the authorities doing?
You are reminded that if your water exhibits a musty earthy taste and smell, especially in the Cape Flats areas, authorities advise that this is due to geosmin, a harmless organic compound apparently originating from the very low Theewaters Dam.
City of Cape Town advises that steps are being taken to access underground water from the Table Mountain and Cape Flats aquifers. Water pressure is being reduced where possible. Consideration is also being given to recycling processed waste water. Greater restrictions seem to be inevitable.
How to prepare your household for current and future water shortages?
Rainwater harvesting by households in SW Cape should be a part of any fresh water management solution. Read more about how much water can practically be saved and economic considerations for rainwater capture systems here.
Installing some form of rainwater capture and water storage system at your home seems to be increasingly wise. At absolute minimum, one can probably get by on 25 litres per person per day. So a 4-person household can survive on about 100 litres per day for all purposes combined. A 1000 litre tank would last for about 10 days and, in the Cape between April and September, one should receive enough rain captured off a 60-80 sqM roof area to refill that tank 2-3 times per month.
And it doesn’t have to be sophisticated or complicated. The tank must be located on a firm hard, level surface as high as possible on the property to harness gravity for the outflow. Simple piping or flexible hose can be used to connect gutters to the tank and a hosepipe used to bring the water into the house. A rough rule-of-thumb is to install 1000 litres of tank capacity per 60-70 sqM of roof area from which water is to be captured as a 10mm sharp shower of rain should then half-fill that tank.
At the moment 1000 litre tanks are available for about R2000, 2500 litre tanks for R2900 and 5000 litre tanks for R5150 and the piping will add a few hundred Rand more. Not cheap but affordable. The basic question to ask yourself is “what will the alternative cost and effort be to fetch and transport water if the taps do run dry“?
Read about a D-i-Y household rainwater harvesting and tank system installation here.
Will the weather help?
The NOAA Climate Centre’s latest report indicates that sea temperatures are edging up in the Pacific Ocean off South America, pointing to the possible re-emergence of a weak “El Niño” event during the second half of the southern hemisphere winter. Interestingly, the situation is uncertain to the point that the possibility of a colder La Niña event is also growing, albeit less convincingly.
The following two charts show the NINO 3.4 [a broad area roughly midway between Australia and South America] sea temperature development over the past month. At the moment the temperature rise remains in the range of 0.0 – 0.3 degC above average [El Niño commences at 0.5degC above].
I should mention that one climate study group claims that higher than average rain can result from an El Niño in certain parts of the SW Cape. Unfortunately recent experience with El Niño conditions has seen reduced rainfall in the catchment areas of the main dams. It seems that the best that can be said is that arrival of another El Niño certainly means that the rainfall during the second half of winter could be either above- or below-average.
For now, the NOAA Climate Centre continues to predict that southern Africa should enjoy normal average winter rainfall.
Occasional rain showers have been arriving as predicted but the rainfalls have mostly been light and of short duration. Unstable weather is expected around mid-April and end-April with the possibility of some general rain and thunderstorms on the latter occasion. A sustained period of unstable weather is foreseen for middle May and, encouragingly, a spell of rain is still being predicted for early in June.
However, our concern is that predictions are still no better than average, or chance – no solid, widespread and sustained rainfall is predicted at this stage during the coming 90 days.
Read ShowMe’s ideas to reducing indoors use of water here.
Read ShowMe’s ideas to reducing outdoors use of water here.
In Summary: net outflows increased again last week and stored water fell from 26.8% to 25.3% of full capacity. At present consumption rates, 72 days supply of generally accessible fresh water remains in the main dams.
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 a D-i-Y household rainwater harvesting and tank system here
Our water-wise landscaping and water-wise gardening suggestions.
Guide to reducing outdoors use of water here.
Guide to reducing indoors use of water here.
Read about South Africa’s desalination policies and initiatives.
Details of level-3B water restrictions here.
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).
Note: To calculate number of days of water left we first reduce reported water stored volume by 10% of capacity (i.e. 89 Million cuM) to allow for water that usually can’t be extracted or processed and then divide the remainder by the net outflow rate during the previous week.
Tom.
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.