A reduction in mining and industrial effluents in the Blesbokspruit Ramsar wetland, South Africa: Has the quality of the surface water in the wetland improved?

Annie-Estelle Ambani,Harold Annegarn

doi:10.4314/wsa.v41i5.08

Annie-Estelle Ambani, Harold Annegarn

Open Access

https://doi.org/10.4314/wsa.v41i5.08

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Abstract

The Blesbokspruit Wetland, 40 km southeast of Johannesburg, South Africa, was listed as a Ramsar Wetland of International Importance in 1986. Following discharges of mine-waters in the mid-1990s, the wetland no longer complied with the Ramsar criteria. This paper reports on historical trends in surface water quality of the Blesbokspruit, as a step towards restoration to Ramsar status. Monthly water quality data (SO 4 , Na, Cl and Mg concentrations, pH and EC values), from January 2000 to December 2011, were obtained from Rand Water for sites at: the stream inflow, just after the discharge point of pumped underground mine-water from Grootvlei mine, and the stream outflow point. The major ions were grouped into two distinct time-variation patterns (SO 4 -Mg) and (Na-Cl). Despite extensive reports that the wetland had an acid mine drainage problem, the pH values over an 11-year period were constrained within a range of 6.7 to 8.8. In 2011, following the cessation of underground mine-water pumping operations, mineralisation of the Blesbokspruit showed a large stepwise reduction, in contrast to a slowly decreasing trend over the previous 10 years, in both the SO 4 -Mg and Na-Cl groups, and EC. The stepwise reduction suggests that the pulping plant within the paper mill, a major source of Na-Cl rich effluent, had ceased operations coincidentally with the cessation of underground water discharges. This contradicts previous findings that underground mine-water discharge was the principal contributor to contamination of the Blesbokspruit Wetland. So, while the Blesbokspruit may have had a high mineralisation problem, this was not simply an acid mine drainage problem, but a combination of the effects of mining and industry. Keywords : acid mine drainage, underground mine-water, Blesbokspruit, Montreux Record, Grootvlei Mine, water quality, circumneutral, Ramsar

Highlights

Dewatering of mine shafts contributes large quantities of poor quality water to the Blesbokspruit
B5 28°28'48.22''E Site located at the inflow of Blesbokspruit 26°12'52.63''S Wetland — receives runoff/ outflow from upstream water users/ land use, such as ERWAT’s Welgedacht and McComb sewerage works, Welgedacht road, Geduld Mine tailings dam, Cowles Dam, Sappi Enstra paper mill, and residential areas
Site located within the wetland, downstream of Grootvlei Mine Shaft No 3 discharge point of pumped underground water (1995–2010)

Summary

Introduction

Dewatering of mine shafts contributes large quantities of poor quality water to the Blesbokspruit. 40 km south-east of Johannesburg, between 26° 12'S – 26° 23'S latitude and 28° 29' – 28° 32'E longitude, is the Blesbokspruit Wetland, designated by the Ramsar Convention as a Wetland of International Importance (Haskins and Compaan, 1998; Ekurhuleni Municipality, 2008). This wetland is one of the largest in Southern Africa, and the only Ramsar site in Gauteng Province, covering an area of 1 858 ha in the Ekurhuleni Metropolitan Municipality, at an altitude of 1 585 m amsl (AngloGold Ashanti, 2004; Ekurhuleni Municipality, 2008; Du Plessis et al, 2014). The wetland serves as a buffer for the water entering the Vaal River, the main source

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