The present water crisis in South Africa, and the possibility that it may be a long-term situation, has meant that we need to find innovative ways to build roads. Water-wise construction means that SANRAL has to conserve water, as well as use it efficiently.
There are three main ways to do this:

South Africa is an arid country that has sufficient groundwater recharge from reasonable rainfall most of the time. Water sources other than surface and ground water need to be developed, including acid mine water, seawater desalination, groundwater augmentation, deepseated 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.

Using and modifying construction materials that use minimal amounts of water. Some of these ‘problem materials’ form holes

when combined and used with other materials to construct roads. These holes allow water to fall through and waste water that needs to be saved. Through nanotechnology, it is possible to modify these problem materials by covering them with ‘mini raincoats’– 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.

‘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 concentrating it.
The reverse osmosis cooling (ROC) process involves removing solutes (such as salts) from seawater and acid mine drainage. 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. It can be successfully implemented in old mining and coastal areas with limited or no water for construction. It will ensure sustainable economic development, in high-risk metros and local municipalities, as well as feasible villages.