Effects of wetlands on water quality and invertebrate biodiversity in the Klip River and Natalspruit in Gauteng, South Africa

Abstract

The Klip River catchment is one of the most heavily impacted river systems in South Africa and is subjected to various types of pollution. The catchment furthermore serves all five recognised user groups identified by DWAF (domestic, agricultural, recreation, industrial and the natural environment). Increasing rates of urbanisation, industrialisation and population growth have aggravated the significance of water pollution as a threat to the wetland resources in the Klip River catchment. A wide range of physical, chemical and biological variables has been evaluated at the inflow and outflow points of the Klip River and Natalspruit wetlands to determine the effects of the wetlands on the incoming water. The Klip River wetland is impacted upon by mining and industries before the inflow points; three wastewater treatment works during the course of the wetland and informal settlements. Analyses of the wetlands show a significant improvement in conductivity, dissolved oxygen, manganese and sulphate concentrations. A deterioration was found in the suspended solids, chloride, sodium, nitrate and phosphate and chemical oxygen demand concentrations. Microbiological analyses showed that there is 93% removal of faecal coliforms from the wetlands at the output site. There was an increase in the SASS4 score from the inflow to outflow points for both the summer and winter months analysed showing a change from a considerably impaired condition to a moderately impaired condition. The Natalspruit wetland is impacted upon by mining just before the inflow point, industries, three wastewater treatment works during the course of the wetlands and informal settlements. Readings taken at the outflow point of the wetlands show a significant improvement in conductivity, pH, chloride, iron, manganese, sodium, and sulphate concentrations. A deterioration was found in the fluoride, nitrate and phosphate concentrations. Microbiological analyses show that there is 99% removal of faecal coliforms from the wetlands at the output site. There was a slight increase in the SASS4 score 6om the inflow to outflow points for both the summer and winter months analysed showing that it is in a considerably impaired condition. Load analyses of the Natalspruit wetland showed improvements for all the physical, chemical and microbiological analyses carried out. Very little work is done on the Klip River wetlands, and any information with regards to their benefit in being in a catchment especially one as degraded as the Klip River catchment, will result in their importance to all South Africans to be highlighted. Mines, industries and wastewater treatment works, can use wetlands as an added measure to purify water before discharging into rivers. In comparison, the Natalspruit wetland is functioning more efficiently than the Klip River wetland. Some reasons for this will be discussed.