A groundwater survey of the greater Durban area and environs, Natal, South Africa

Generally, surface water supplies have been able to satisfy requirements in the greater Durban area and environs. The exceptions have been in relation to water use for agricultural purposes and the provision of water for rural villages. However, the major droughts of the early 1980s and 1990s, together with the burgeoning expansion of the population, mean that significant additional water supply will be needed in the future. The rock types in the area include the granites-gneisses of the Basement Complex, the sandstones of the Natal Group, the tillite of the Dwyka Formation, and the shales and sandstones of the Ecca Group. The latter, in particular, have been extensively intruded by dolerites. These rock types represent secondary aquifers in which generally limited supplies of water are associated with weathered and fractured zones. Unconsolidated deposits of Quaternary age occur primarily in the coastal zone and represent the primary aquifers. From the evidence of borehold yields, the aquifers were categorized into four groups, namely, those offering high yields, moderate yields, low yields, and very low yields. The quality of the water in boreholes ranged from excellent to saline. It is estimated that up to 7% of the mean annual precipitation goes towards groundwater recharge so that the available groundwater resource should satisfy future demand, especially in rural areas.