OVERVIEW OF THE IMPACT OF MINING ON THE ... - IIED pubs

The Phalaborwa Water Board has been delegated the responsibility for all aspects of water supply to, and
effluent discharge from, the town of Phalaborwa. In addition, the Board also controls flow releases from the
Blydepoort Dam on the Blyde River. Small irrigation boards control the allocation of water for irrigation in the
upper reaches of the Selati River.
5.7.1.6 Human impacts on water resources (excluding mining)
Given that the lower reaches of the Selati River are “normally” seasonal, but now are perennial as a result of
continual seepage and effluent discharges from Phalaborwa and its mines and industries, it is difficult to
separate “non-mining” impacts from those that are directly attributable to mining operations. Nevertheless, an
impression can be gained by comparing the analyses of water samples collected upstream and downstream on
the lower reaches of the Selati River with those in the nearby Olifants Barrage and the Olifants River nearby
(Table 5.13).
What is immediately evident is that the quality of the water in the Selati River immediately upstream of the town
of Phalaborwa is already very poor, probably as a result of agricultural return flows and other effluent discharges
upstream. After the inflow of the seepage and effluent from Phalaborwa, the concentrations of a few
constituents increases but there is no overall improvement or worsening of water quality. In contrast, the water
quality in the Phalaborwa Barrage is comparatively good and, when mixed with water from the Selati River,
there is a marked deterioration in water quality as shown by the results for Mamba Weir (Table 5.13). At the
time when these samples were collected, September, the flow from the Phalaborwa Barrage was almost exactly
equal to the flow of the lower reaches of the Selati River, approximately 0.5 m 3 /second; this would suggest that
the water from the Selati River would have been diluted by about 50% by water from the Olifants River.
Table 5.13: Comparison of water quality characteristics of samples collected from the Selati River upstream of
Phalaborwa and downstream of all effluent discharges, with water samples collected from the Olifants River at
the Phalaborwa Barrage and at Mamba Weir (B7M015) below the confluence of the Selati and Olifants Rivers.
[All data are given as mg/litre, except ph (log units) and conductivity (mS/metre)].
Parameter
Selati River
(Upstream)
Selati River
(Downstream)
cccxix
Phalaborwa
Barrage
Mamba Weir
(B7M015)
Conductivity 342 358 48 192
pH 7.5 7.2 7.9 7.9
Ca 142 104 26 61
Mg 214 204 25 100
Na 280 325 38 141
K 84 113 1 63
Cl 1,322 1,230 34 128
F 4.3 4.4 0.3 2.1