Classification of water resources within Quaternary Catchment C22K

Abstract

The Vaal Barrage was built by Rand Water downstream of the Vaal Dam. The Vaal River Scheme, in many respects, brought about a change in the environment along the Vaal River between the Barrage and Vereeniging. Vereeniging is located in the lower reaches of the Klip River (Gauteng), close to its confluence with the Vaal Barrage. This town was established on coal mining and steel industries and also hosts Rand Water‘s purification works. This study focused on the classification of water resources and associated aquatic ecosystems within catchment C22K. The reason for the selection of this catchment was the concerns regarding large-scale industrial activities in the catchment and also within catchment’s tributaries. In addition many waste water treatment plants are malfunctioning. System operations are declining especially sewage treatment (DWA, 2011). Sewage discharges often far exceeds the standards and conditions demanded by licences (DWAF, 2004). These key water quality parameters are threshold concentrations which, if regularly exceeded, can result in harmful impacts on aquatic ecosystems and human health (Dabrowski & de Klerk, 2013). Mining activities are polluting both surface water and groundwater resources. An additional concern is the growing number of agricultural activities in the area. Expanding populations and climate change in the region have put additional pressure on the quality of Vaal Barrage water (Riemann et al., 2017). The current state of the water resources and associated ecosystems were determined and management classes were set for the above mentioned. Return flows from domestic and industrial effluent discharges and surface run-off from urban contribute to increase Total Dissoved Solids (TDS). TDS is an important parameters water quality indicator and refers to the degree of salinity of water. In 2016 the TDS value went up to 461mg/l at the Vaal Barrage. TDS value at the Vaal Dam is 116 mg/l. The quality of the surface water at the Vaal Barrage was not natural anymore but good for the ecosystem due to continuous dilution of natural water quality from the Vaal Dam, and the water resource should managed by class I to ensure the water below the Vaal Barrage is fit for use. A vulnerability assessment based on risk and hazard description using local and scientific expertise (DRASTIC approach) (DWAF, 2005) indicates the pollution potential of groundwater quality to the surface water mining being moderately hazardous, Geo-interaction requires management class II response. Increased pollution wash-off and human activity makes the environment less habitable, resulted in moderately modified habitat and water quality degradation. Habitat loss associated with management class II.