Pierre Roux
SOUTH Africa has been gripped by a drought due to climate conditions brought on by global warming. It has had a devastating impact on South Africa, including on road construction. A paradigm shift is needed around our approaches to sustainability and water conservation.

Water scarcity has led to delays in the construction of some roads. New material and road construction technologies must be developed and adopted to reduce the use of construction water, and extreme water conservation methods should be adopted. Without these efforts, roads will become increasingly expensive to build in the future. Water-wise construction is long overdue and SANRAL is focused on finding ways to conserve water and use it more efficiently in road construction for the benefit of the communities where it operates.

Through using the appropriate earth-scientific data sets (geophysics) to benefit the country and community, research opportunities have been created to unlock new, long-term, sources of water and renewable energy.

Through the combined efforts of geologists, students from varying institutions, the Water Research Commission, the Department of Water and Sanitation and the Council for Geoscience, as well as the technological expertise at SANRAL, the

following solutions to address the water crisis are being proposed:

1. WATER AUGMENTATION
South Africa is an arid country, which has sufficient groundwater recharge from reasonable rainfall most of the time. Water sources other than surface and ground water need to be developed. These include acid mine drainage (AMD), seawater desalination, goundwater augmentation, deep-seated shale gas fracking water and deep-seated geothermal water. Groundwater augmentation entails adding excess water into the ground using recharge boreholes. This water reaches the water table and is added to the groundwater reservoir. Groundwater is a renewable yet limited resource with a storage capacity that provides a large and extensive distribution of water supply.
To ensure a successful application, certain conditions need to be met in the areas where this is to be implemented. The land needs to have favourable geological conditions, low groundwater contamination potential, and it must be sustainable to accommodate and maintain this method of water preservation and harvesting.
The social and economic benefits of using this approach include: no construction delays during droughts or water shortages, secure ground water for contractors and claims of lower risks and costs with long-term water security for the community. This approach is one of SA’s most economical and feasible options.

2. MATERIAL MODIFICATION AND WATER CONSERVATION
While building water-wise roads, attempts should be made to use and modify construction materials that use minimal amounts of water. Some “problem materials” form holes when combined and used with other materials to construct roads. These holes allow water to fall through and waste the water that needs to be saved.
Through nanotechnology, it is possible to modify these problem materials by covering them with “mini rain coats” – a layer of coating that allows these elements to be combined successfully. This ensures that these minerals will not form holes when used to construct roads.
For this method to be successful, it should be implemented in remote sites or low-risk environments, in situations where there are low quantities of available materials and water and by workers who have the knowledge to use materials with problem molecules. Technologies

not generally used in road construction, such as detailed mineralogy analysis and exploratory geophysics and desalination, are applied in this approach.
When successful, the benefits of using this technique will result in water-wise roads in dry desert environments with minimal groundwater use for roads, instead of sustainable livestock farming.

3. DESALINATION OF SEAWATER (ROC PROCESS)
Osmosis is the natural process by which a concentrated solution migrates towards a less concentrated solution across a membrane, so that the two solutions have the same concentration of solutes. “Reverse Osmosis” means taking the lower-concentrate solution and making it more concentrated.
The reverse osmosis cooling (ROC) process involves removing solutes (such as salts) from seawater and AMD. The salts are removed using a semi-permeable membrane (like a screen door that allows certain solutes to pass through while blocking others), using a high-pressure pump and electricity, which removes 90-95% of the dissolved salts and leaves the water safe for human consumption.
The ROC process can be successfully implemented in old mining and coastal areas with limited or no water for construction. It will ensure sustainable economic development in at-risk metros and local municipalities, as well as feasible villages.
The socio-economic benefits include lowered operational costs for the end user, no impact on traditional water sources for road construction and the possible use of tidal and geothermal energy.
The broader impact Through any of these methods, more water will be available not only for road construction but for the general consumption of communities.

Pierre Roux is an Engineering Geologist at SANRAL