8.4 Water Quality

The chemical water quality of the Keurbooms River is very high. The water flows over the relatively inert sandstones of the Table Mountain Group. This is in contrast to Roodefontein Dam’s water quality, which is significantly more saline, being located on the saline Enon conglomerates.

Dissolved Iron and Borehole Clogging

Iron-related problems are common in the Table Mountain Group aquifers, specifically in boreholes which target both the Peninsula and Nardouw groups in the Eastern Cape (Smith, 2006). Iron is known to occur in some of the boreholes in the Kwanokathula Aquifer. These should be avoided as a recharge location if possible. An option may be to fix iron in these locations by injecting oxygenated water in this area.

The preferred option for MAR is to use treated water from the Keurbooms River (Murray, 2007) because dissolved organic carbon (DOC) and iron concentrations in the untreated water might encourage borehole clogging and plugging of aquifer fractures around the injection boreholes. Aeration and filtration will usually remove some of the dissolved iron. Treatment also removes dissolved oxygen, which improves the likely success of artificial recharge, particularly if microbial reactions are contributing to the oxidation of iron in the aquifer. Another benefit of treatment is that the water is disinfected by chlorination. It was also recommended that the production boreholes be pumped at a continuous low(er) rate rather than intermittently at a higher rate. This avoids the oxidation and iron precipitation problems in the aquifer and on the steel borehole casing associated with repeatedly raising and lowering the water level which allows aquifer water to flow back into these zones (Tredoux, 2007).


Managed Aquifer Recharge: Southern Africa Copyright © 2021 by Eberhard Braune and Sumaya Israel. All Rights Reserved.