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DESALINATION ONLY PART OF MOTHER CITY WATER SOLUTION

Cape Town will have at least one desalination plant operational before ‘Day Zero’ hits in May, when the citiy’s taps are due to run dry. Various other measures, some possibly temporary, will also contribute to something of a rushed ‘fix’ Cape Town’s climate change-driven water shortage crisis. But climate change’s relentless pressure means both medium-term and longer-term projects around the supply of fresh water to some six million people are inevitable. We take a look.

Recently, City of Cape Town Mayor Patricia de Lille briefed the media during a visit to the Scientific Services Branch at the Athlone Wastewater Treatment Works. The branch monitors the city’s water quality year-round. De Lille was certain that the plans and partnerships ahead of the so-called ‘mega-plant’, due for construction in the harbour area, were well under way, with three more additional desalination plants to be installed before the end of February at the V&A Waterfront, Strandfontein and Monwabisi. ‘Cape Town will have three new desalination plants before the end of February. Two, Monwabisi and Strandfontein, will produce 7 million litres of water per day (ml/day). And then there is the one at the Waterfront that will bring an additional 2ml/day.

The mega-plant that we are looking at for more permanent use is at the Cape Town Harbour and the planning for that has started already. That will produce about 50ml/ day. ‘The Waterfront plant will take the planning from the City and they will be self-reliant after February. It (the City’s response to the water crisis) is (in the form of) partnerships and people who are willing to work with the City,’ explained De Lille. ‘I am proud of Capetonians. At the beginning of 2016 we were using 1.1bnl/day. We are now on 582ml/day. As you can calculate we are (still) 82ml short of the 500ml mark. I am confident that Capetonians will reach the 500ml goal. People must still continue to save water even though we have pushed Day Zero to May, she added.

PUSHED BACK

The dreaded ‘Day Zero’ for Cape Town’s taps to run dry had initially been projected for late March but has, thanks to severe measures on the supply side and a steady drop in demand, been pushed out by at least two months to sometime around mid-May (De Lille said most recently that it would be about May 13), by when, it is widely hoped, the winter rains will have set in. But weather conditions in Cape Town, always tricky to predict, have become even more so under the increasingly evident effects of climate change. Driving the drought has been a super-severe El Niño effect – raised surface sea temperatures in the Pacific Ocean off the west coast of South America moving westwards – which has recently and suddenly switched over to the a La Nina effect, which is much the same but in which there is a cooling of sea-surface temperatures in the equatorial Pacific Ocean which, in turn, influences atmospheric circulation. Both effects have far-reaching global implications as they can, alternatively, cause droughts and heat-waves or major flooding in regions in both Northern and Southern hemispheres. The reason Cape Town and its surrounding region of the Western Cape have been so badly hit is the culmination of two factors:

• This past El Niño lasted for 25 months from 2014-16, the longest and hottest on record (the previous longest was 24 months, 1957-59, and covered two winters).
• By dint of timing this just past El Niño affected three winters creating a special low rainfall problem for the South-Western Cape. This has resulted in a drought that is being described as the worst in living memory, but is likely to be both one of the worst the region has had in the last several hundreds to thousands of years, and may well be an indicator of similar things to come.

IMPLICATIONS

As the implications of climate change have sunk in with authorities empowered to head off such disasters, it has become clear that looking even a few years into the future we may be seeing just the beginning of a continued and in essence permanently drier climate regime setting in for this region. Late spring and early summer downpours instigated by the extremely unusual intrusion of the normally more easterly-lying Inter-Tropical Convergence Zone (ITCZ), which keeps most of the Sub-Saharan semi-tropical Western, Eastern, Central and Southern African zones well watered in summer months, has also meant a small boost for Western Cape dam levels.

This ‘strange’ weather pattern has seen the ITCZ shift dramatically westwards and southwards in recent weeks such that it stretched down the full length of the western coast of Africa, right through Namibia (very unusually) and across the northern and central regions of the Western Cape, reaching right down to Cape Town itself. The result has been a series of dramatic thunderstorms and some intense weather systems more normally associated with the Highveld and the hinterland summer rainfall season, plus some welcome rainfall for Western Cape dams, and even a very late season cold front that, in the third week of November, dumped snow across some high-lying regions of the Western Cape, Eastern Cape and the Drakensberg. The short story is, as almost everyone now knows, that ‘normal weather’ may happen, but it is going to happen less frequently over time while unusual or ‘abnormal’ weather will become increasingly frequent – in other words, ‘no more normal weather’ in terms of planning, service provision, distribution patterns, farming activities and a host of other impacts. The South African Weather Service said in late September, prior to the weird ‘summer rainfall’ type weather on late October and November, that it was forecasting a ‘weak La Nina’ weather pattern to develop in the early summer, raising expectations for above-normal rainfall across large swathes of the country, including parts of the maize belt. But it cautioned in its five-month forecast that the severe drought in the southwest of the country, which includes the tourist hub of Cape Town, was expected to worsen despite forecasts for above-average rainfall.

RATIONING COUNTRIES

It is therefore entirely not surprising and correct that Cape Town’s water authorities are saying that even if there is more ‘unusual’ summer rainfall for Cape Town and its surrounds, and even if the 2018 winter rainfall season starts early and strong, harsh rationing is likely to continue – for the foreseeable future at least, and maybe permanently. Said De Lille: ‘This is our new normal – we’re in a permanent drought and we must get used to the fact that water will never be in abundance again.’ The Dutch government, which is experienced in the area of desalination, has already met with SA’s national government, and a meeting with the City authorities was imminent. ‘We have already brought additional water from the Molteno reservoir in Oranjezicht and the Atlantis
aquifer, with 2ml/day and 5ml/day from these sources, respectively. At this stage, there are seven projects already under way in the first phase,’ she added. These projects are Monwabisi, Strandfontein, the V&A Waterfront, and Cape Town Harbour desalination plants; the Atlantis and Cape Flats aquifer projects; and the Zandvliet water recycling project, which will be producing an additional 144ml/day between February and July.

To keep essential services and vital industry running, the City authorities will, at the 13.5% dam storage level, turn off almost all taps. This will directly or indirectly affect about six million people in greater Cape Town and its surrounds. Despite that scenario being daunting as a prospect, De Lille remains upbeat: ‘That is Day Zero. But if we all work together to continue to save water, that day may never have to come.’ If it does dawn, millions of resident of one of the world’s leading tourism destination centres will have to collect a predefined amount of drinking water per person a day from about 200 collection sites across the city. The quantity of water distributed would be based ‘on the minimum requirements for people to maintain health and hygiene’. At present, the plan is to distribute 25l/day per person, which is in line with the World Health Organisation recommendation.

DESALINISATION OR NOT

While the UAE, the Israelis and others have gone far in the world of cost-efficient desalinisation (most modern plants work with reverse osmosis technology rather than other more energy-consumptive solutions), it has become clear in the scramble to avoid ‘Day Zero’ in Cape Town that desalinisation will not, on its own, be sufficient to deal with the problem, either quickly or permanently. Cape Town’s planning authorities say they will bring various ‘reserves’ or alternative water supplies on line incrementally from modular desalination plants, groundwater abstraction and water reuse. These plans will be at different locations across the city. In the medium term, Cape Town needs at least one, preferably two (for redundancy purposes) large-scale
desalination plants in the order of 300-400ml/day. But building even one will be a multi-year project.

Because the current challenge is firstly a short-term crisis, the city authorities have opted instead for not one large-scale desalination plant – at least, not yet – but several elements to formulate a short-term response. The resort to multiple smaller and incrementally introduced plants and alternate water supplies has allowed the planning authorities to ‘respond quickly and adapt to the drought’.The promise from De Lille and her specialists is the Cape Town will not actually run out of water and that ‘Day Zero’ will be avoided. That may be true for early 2018, but it is clear from how rapidly and unexpectedly (for some) the Cape Town water crisis has come on, that there are going to be further challenges down the line – groundwater, for one thing, relies ultimately on absorbed run-off from rains and if the rains are not coming then groundwater too will run dry at some point (with attendant other problems that are not for discussion in this article).
So while, for the time being, several small-scale desalination plants at multiple locations will inject water into existing infrastructure, within the constraints of that infrastructure, in a process that will come online ‘in a matter of months’, and other water ‘reserves’ will be tapped, it is obvious and inevitable that large-scale desalinisation as an addition to – and perhaps eventually, as the main source of – Cape Town’s fresh water storage and recycling system is inescapable. 

 

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