The Vaal area forms part of the Highveld, this name refering to the high interior plateau of South Africa which is fairly flat with elevations varying from 1 500 m to 1 800 m above sea level. The area is situated south of the sub-continental divide known as the Witwatersrand Ridge which stretches east to west across Johannesburg. the rain falling south of this ridge flows via the Vaal River into the Atlantic Ocean.
The Vaal River Basin is the main hydrological system in the area whose tributaries are non-perennial due to the dry weather. The Vaal Dam is an important source of water for the area, supplying a continuous flow of good quality water into the Vaal River. The two main tributaries of the Vaal River are the Klip River and the Suikerbosch River.
The Vaal area covers falls within the Grassland Biome, which covers the high central plateau of South Africa. About one third of the mammal species of South Africa occur in this biome. Highveld vegetation consists of a combination of grassland types with moist types present towards the east and drier types towards the west and south. Much of the area is covered by Cymbopogon Themeda Veld type 48b. Trees and shrubs such as Protea Caffra are common along rocky hills and ridges. Much of the original habitat has been greatly reduced due to farming and modern developments.
Rock types include sandstone, quartzite, mudstone, basalt and biotite granite. Soil texture types include sand-clay-loam, clay, sand-clay, sand-loam, loam-sand.