Posted by: Saving Water SA (Cape Town, South Africa) – partnered with Water Rhapsody conservation systems – 06 December 2010
Tens of thousands of migrants pouring into Cape Town are forcing authorities to rethink the city’s water supply strategy.
“There are quite large numbers of people coming in and the city needs to review its water-use growth strategy,” department of water affairs’ Western Cape chief director, Rashid Khan, told Sapa.
He said assumptions made by Cape Town’s water planners in 2007 were “now being overtaken by some serious developments, that is (population) growth”.
His remarks followed an announcement by the department that it was “exploring initiatives to ensure that water use in and around Cape Town does not outstrip supply in the near future”.
It had recently learned that “water use may be growing faster than anticipated”, despite significant successes achieved by the city in reducing water usage.
“An increase in demand could have serious implications for the supply area, as the next augmentation project may well have to be fast-tracked to ensure an adequate supply of water to every city, town and industry that gets its water from the Western Cape Water Supply System (WCWSS).
“These include the City of Cape Town and towns such as Stellenbosch, Franschhoek, Saldanha and Paarl,” it said.
According to Seth Maqetuka, director for strategic urbanisation in the city’s housing directorate, so-called “migration growth” now outstrips Cape Town’s “natural” growth rate.
He said migration growth was now “16 000 households per annum” compared to natural growth of 11 000 households a year.
The city works on an estimated five people per household, so, taking the above figures into account, its population – 3.7 million, according to a 2010 estimate provided by Maqetuka – is growing by about 135 000 people a year, of whom about 80 000 are migrants.
Figures on the city’s website show that in 2006, Cape Town’s natural growth exceeded migration growth, which suggested a big spike in the number of migrants over the past four years.
“Most of the in-migration to Cape Town comes from the Eastern Cape,” the website states.
Maqetuka said the city did not have any recent migration statistics, but conceded that “it is likely that migration growth is greater than natural growth”.
Khan warned that Cape Town could not continue being almost totally dependent on rainfall for its water supply.
“The city… is one that relies about 90-odd percent on storage of water… 90-odd percent falls in winter; 90-odd percent is used in summer. You have to store water.
“Water security is based 100% on rainfall. And that is where I am not comfortable… We only need one year with little rainfall, and then the dams run dry,” he said.
While the city still had spare capacity, thanks to the recently-completed Berg River Dam, the time had arrived for it to institute “augmentation” efforts, in the form of stricter demand management, recycling, desalination and ground water supply, among others.
“At the moment we’ve got a surplus… but, looking at the high water requirement curve, we’ll reach capacity by 2012/13 if there is no water savings… With water savings, we will reach this point in 2018.”
Currently, the city used about 331.8 million m³ of water a year.
Khan said the national department had given Cape Town R17.5m “to make sure they are 100% successful with water saving”.
If such savings – to be achieved through water demand management and water re-use (recycling) – did not suffice, the next step was desalination.
“This will give us 66 million m³ a year, almost the volume of the Berg River Dam…. This is considered expensive, but if it is a high-growth scenario, we’ll have to go there,” he said.
It is understood a site near Eskom’s Koeberg nuclear power station is being considered for a desalination plant, to take advantage of the off-peak power the utility could supply.
“Desalination may be an expensive option when you have other water, but it is the only option if you don’t have any rainfall… Less reliance on rainfall; that will give us better water security,” Khan said.
He further noted that the effects of climate change, if severe, could bring forward the construction of augmentation projects.
Climate forecasts for the next few decades do not bode well for the region’s water supply.
According to a 2005 department of agriculture report, the Western Cape “is likely to become warmer and drier over time…(with) reduced water in the rivers”.
Khan said national, provincial and local government were working on a joint 25-year water strategy plan.
He said the city had done well with its water management in the last decade, and had achieved “significantly more than” the 20% water-savings target it had agreed to in 1999.
Ninety percent of the city’s current water demand was for domestic and commercial use, with the agricultural and industrial sectors “not significant” consumers.
The strategy plan also included the use of ground water.
The city had “not moved seriously” on ground water use, but was now looking at this option.
“I would be more comfortable if we had more ground water to give us back-up,” Khan said.