Cape Town City water augmentation efforts
What of augmentation efforts to produce extra fresh water?
The table below reflects the current situation of Cape Town’s augmentation efforts as at July 2018.
Keeping it in perspective, augmentation at best provides a minimum life-line in a survival situation but cannot be expected to make a significant contribution to fresh water supplies until end-2020.
Consider this: even if the initiatives outlined below all come to full fruition on the dates shown they will, across the whole of year 2018, produce only around one third of the surface run-off received from the rainfall into the dams in one week alone. I.e. just two days of rain produced more water than is expected from all the augmentation efforts for the whole year 2018.
Here is our updated summary chart (click the chart for an enlarged picture).
Details of the augmentation plans are starting to crystallize. Why is this important? Well, once “what will be done by when” is set down, then a picture of available water volumes and costs begins to emerge. This in turn, enables the household, business and agricultural sectors to start to firmly plan and invest with more confidence. And from this, of course, comes activity and production resulting in growth, employment and improved general well-being. A clear picture eliminates uncertainty.
The emerging plan foresees a balanced array of extra water production initiatives. What are these?
– maximise water from existing and supplemental surface water systems (dams and rivers). This is mainly in the hands of DWS. [max 65 ML/d]
– groundwater abstraction from both the sandy Cape Flats and Atlantis aquifers as well as from the deeper TMG strata. This will likely be the second largest contributor of fresh water. The process has the added capability of being switched off when adequate surface water is available. [max 140 ML/d]
– recycling will extract usable water from existing waste water flows at an advanced processing facility planned to be built at the Faure waste water facility. [max 70+ ML/d].
– at least one large scale permanent seawater desalination plant will be built, probably on the west coast, to provide around 120 ML/d of fresh water, both contributing to overall supplies and as a life-saving source in unlikely event of failure of all the other water supply systems. [max 125 ML/d]
– an improved method to divert and harness storm water for aquifer re-charge purposes. [??]
The augmentation effort has initially taken the form of groundwater abstraction from Atlantis, the three small temporary desalination plants at Strandfontein, Monwabisi and V&A Waterfront, and a small interim recycling facility at Zandvliet. Intended to provide water in an emergency and otherwise to test and prove the concepts, it is intended that all the temporary plants will be discontinued and replaced by permanent installations within three years.
And how is it going?
1) Extra water production is coming on stream as expected, with overall extra water supplied into the system reaching 45 ML/day as at end-July 2018. So far the outcome is according to plan.
2) There is a challenge related to the Atlantis well-field in that the cost of piping that water directly to Cape Town is proving to be (unacceptably) high. Alternatives are being considered to rather pipe the water to the VoelVlei reservoir and from there route it to Cape Town but also to have it available to serve the west coat area and Saldanha Bay. Steps may also be taken in time to encourage water-hungry industry to relocate to the Atlantis area to better use the available water where it is. Extra water production from this well-field operationally fluctuates between 5 and 12 ML/day.
3) Progress to access the Cape Flats aquifer is proving slower than hoped. There is no change to the long-term targets and work is progressing according to the DWS licence conditions. However, for the first two main points, at the first one the quality proved to be poor and extra technology has to be applied to correct this, whereas at the second point where the quality and volume are both good, a land-owner has decided to interdict and stop the project. Work is progressing on City-owned land and at the airport, but the water yield volumes are less than expected.
4) For the TMG aquifer the decision is to concentrate initially at Steenbras where TMG ‘Peninsula strata’ containing the water runs under the dam catchment. It had been hoped that this would prove to be a simple abstraction, with the water emerging from boreholes under artesian pressure and that it could be simply allowed to run into the dam for onward processing. Well that was also not to be. Environmentalists have intervened and obliged the installation of piping systems to make sure that the water does not harm the native fynbos on its way to the reservoir. Extra care is also being taken to prevent harm from the material produced by the borehole drills. Lastly, tests have revealed that the aquifer water is heavy with iron needing pre-processing to reduce this iron content before adding the water into the reservoir. These are all items that will increase costs and slow the implementation.
5) The temporary desalination plants have come on line as planned. The City has decided not to accept supplies from the V&A unit as it is proving to be too expensive. It had initially been thought that the V&A might keep this plant operating beyond the end of the initial 2-year period but that may now also prove to be impractical as its high cost of water production could substantially exceed the cost of other water supplies at later lower restriction levels.
6) The city is proceeding with a desalination ‘pilot plant’ to be co-located at Koeberg nuclear power station. Creating such an installation alongside a nuclear facility brings its own complications due to the demanding operating regulations set down by the nuclear regulator. Additionally, extra quality testing will be needed to ensure there is no pollution of the water produced there.
7) Plans are proceeding for the establishment of a utility scale desalination plant. International experience shows that currently the optimum size for a desalination plant is in the range of 120-150 ML/day capacity. A modular unit is envisaged perhaps commencing at 50ML/day capable of being ramped in stages up to 150 ML/day capacity. Studies are progressing to determine the best physical sites that will permit maximum efficiency of operation, minimised environmental impact, proximity to adequate power supplies and water reticulation injection points. Additionally, placement of such a plant should match the new spatial plan for the Metro which envisages greater densification of populated areas. Due to the relatively heavy impact of desalination processes on the environment, once potential sites are chosen, environmental Impact assessments need to be conducted. Realistically, it is likely to take 3-5 years (and possibly as long as 7 years) for such a desalination plant to come in to production.
During this process there has been a shift in emphasis from desalination toward groundwater (which is relatively more available, cheaper to access and quicker, easier to implement) and to recycling.
Assuming reasonably normal average rainfall, it is expected that these steps together will provide water resilience and security for the SW Cape for at least 10-15 years.