As the Western Cape’s dams have fallen to only 30% of water storage capacity in May 2016 from 72% in May 2014, Cape Town has imposed water restrictions from the beginning of the year to conserve water.
Climate change will result in more frequent and severe weather events, increases in temperature in many regions and resulting changes in precipitation patterns. This may result in rainfall in the Western Cape falling by 30% by 2050, even as the city’s population increases it is attracting migrants from other provinces.
The combination of decreasing rainfall and increasing population means there is an urgent need to build more water storage dams in the Western Cape so that economic progress can continue.
This was why the Minister of Water and Sanitation, Ms Nomvula Mokonyane, said in her keynote speech at the 84th annual conference of the International Commission on Large Dams (ICOLD) in Johannesburg last week that the department was looking at new dams and new water transfer schemes.
“This year's drought has also opened up our eyes to invest more on water transfer schemes. As a department, we should be able to transfer water from areas of high supply to those under stress when the need arises, thus my department is investigating the possibility of building more of these schemes. We have also commenced with the feasibility study on a project to augment water supply to the City of Cape Town and the surrounding areas,” she said.
The ICOLD symposium is being held at the Sandton Convention Centre with some 1,200 delegates from 77 countries (of which 24 are from Africa) attending.
Water-stressed South Africa has been looking for ways to supplement the natural water of South Africa’s industrial heartland, the Gauteng province, for decades with feasibility studies undertaken in the 1950s that showed that the water supplied by gravity feed from Lesotho was more economically than trying to pump water from the lower-lying Orange River to the high-altitude Gauteng.
It was not however until the 1983 and 1985 droughts brought home the impact of how dire the need was with water having to be pumped from the Vaal River to the Mpumalanga coal-fired power stations, that a treaty between Lesotho and South Africa was signed in 1986. The original treaty envisaged several phases, but so far only Phase 1A (the Katse dam and water transfer tunnel to South Africa) and Phase 1B (the Mohale dam and water transfer tunnel to Katse) have been completed. At peak construction, the former provided some 22, 000 jobs and the latter 15, 400. Total project was near R17bn.
In 2011, the treaty regarding Phase II, which envisages an increase in the current supply rate of 780 million cubic metres of yield per annum to more than 1,260 million cubic metres per annum, was signed. The original time line was that first water transfer would take place in 2020, but this has been moved to end 2024 due to slippage in the project implementation in part because of the political turmoil in Lesotho.
The Phase II will cost some R23bn and will see the building of the 163m high Polihali Concrete Faced Rock Fill dam, as well as the 38km water transfer tunnel between Polihali and Katse.
The new project time lines are given below.
Not included above is a possible 1,000 Megawatt pumped storage scheme at Kobong similar to the one at Steenbras.
Given the recent problems with electricity supply from Eskom, Minister Mokonyane said 14 dam sites have been identified for retro fitting with hydropower turbines.
“The total technically feasible hydropower potential is estimated to be 11, 000 Gigawatthours per year. We cannot continue to design and build dams which will address our water challenges and not be innovative enough to address our other socio-economic issues. The Mzimvubu dam project will serve as a good example of how we should think innovatively as it will be a hydro-power scheme,” she says.
The department’s 2013 annual report found that 37% of potable water was lost through leaking pipes and dripping taps. The report also noted that water demand had already overtaken supply by 60% in water infrastructure management areas and that over 30% of the country’s waste water treatment plants were in a critical condition.
Slippage in project times lines are not confined to the Lesotho Highlands Water Project as the first phase of the Mokolo and Crocodile Water Augmentation Project (MCWAP) in Lephalale area in Limpopo in 2015 was completed two years behind schedule. It is now operational and has the capacity of providing 30 million cubic metres of water per annum to Eskom’s Medupi power station. MCWAP’s two-phase construction included building several large pump stations, over 170 km of pipeline and an abstraction works, which all required supplementary infrastructure.
“Raising the Clanwilliam Dam wall in the Western Cape involves raising the existing dam level by 13 metres and will result in an additional 70 million cubic metres of water a year to farmers downstream,” Mokonyane said.
The dam level is critically low due to unusually dry seasonal weather, causing water shortages in the Cederberg and Matsuyama local municipalities who rely on the dam for their water.