Due to extensive utilization of water from the Vaal River upstream of Midvaal’s abstraction point, water in this stretch of river is typically high in dissolved solids and contains high amounts of dissolved organic carbon and plant nutrients like phosphate and nitrate. This indicates that the water is “hard” or mineralized (due to the levels of salts like calcium, magnesium, sodium, chloride and sulphate) and contains numerous types of algae and other nuisance water plants like water hyacinths and water grass (due to the high levels of phosphates and nitrates).

The quality of the river water varies seasonally, as rainfall impacts on the turbidity, mineral levels and on the nutrient levels.

Raw water is abstracted from the Vaal River by means of large pumps, situated in the intake tower, and pumped through pipelines to the treatment plant for purification.