African Wildlife and Environment Issue 65

CONSERVATION

CONSERVATION

it starts to spread out horizontally in sub-surface aquifers, typically the dolomite compartments. ECL is defined differently by the DWA study (second column) when compared to an earlier study by the Trans Caledon Tunnel Authority (TCTA) study (third column). The recorded flow of AMD from each is listed in the fourth column, with variability caused by the ingress of rainfall. The total dissolved solids (TDS) is measured as mg/l, also known as parts per million (ppm), and is shown in column five for the DWA study, and in column six for the earlier TCTA study. From Table 1 we can therefore calculate the flow into the river systems draining the Witwatersrand Goldfields. This translates into 99 Ml/d during low flow condition, and 229 Ml/d during high flow

condition. The Western Basin discharges into the Crocodile River system via the Tweelopiespruit, but the runoff from surface tailings dams’ discharges into the Vaal River system via the Wonderfonteinspruit. All of the other basins discharge directly into the Vaal via either the Klip- or the Blesbokspruit (see Figure 1). With these flow figures, we can calculate the salts loads entering the combined river systems. Using the more conservative TDS data shown in column five of Table 1, the total system load is shown in Table 2. Therefore, using the government’s own primary data, and the more conservative figures for TDS load, we have 439,092 kg/d entering the system under low flow conditions; which more than doubles to 982,452 kg/d under high flow conditions. In layman’s

Separating fact from fiction: WATER QUALITY IN RIVERS draining the Witwatersrand Goldfields

The recent election of Donald Trump to the Presidency of the USA has heralded in the concept of ‘fake news’. This has rapidly taken root in South Africa.

The following statements have been made regarding the acid mine drainage (AMD) treatment plant that was opened in the Eastern Basin in February 2017: “By producing fully treatedwater that will significantly increase water supply to the Vaal River System, the opening of the Springs AMD plant will respond to the pollution of freshwater, and stop polluted mine water from reaching a certain level below the surface‚ which affects the country’s water sources” said Mokonyane as quoted by Mining News (20 February, 2017) (emphasis added). The same article claims that this specific action “will help secure water for the next 30 years” from “the largest of the three plants (the others being in the Western and Central basin) and the largest of its kind in the world, with the capacity to clean 110 megalitres of a water a day, and send the water back into the Vaal River system” (emphasis added). A different article covering the same event quotes the following: “Speaking during the launch of the plant, Mokonyane said: ‘This planned intervention was to turn the AMD problem into a long-term sustainable solution, by producing fully treated water that will significantly increase water supply to the Vaal River System and defer the need for further costly augmentation beyond Phase 2 of the Lesotho Highlands Water Project, for at least another 30 years’” ( Daily Maverick , 24 February 2017). It goes on to say that, “It is certain that were it not for the timeous intervention of the department the upshot of this would have been the contamination of the

Prof Anthony Turton

TABLE 2 Total Salts Load Entering the River Systems Draining the Witwatersrand Goldfields

freshwater flowing into the Vaal River System, spelling dire consequences for the public.” (Emphasis added). This is clearly a good news story. Or is it? Focus now on the underlined portions when reading the rest of this article, because a closer analysis of the facts reveals a highly nuanced but very real ‘alternative truth’. In an official Department of Water Affairs (DWA) study made public on 7 September 2012, the data shown in Table 1 was presented. The Witwatersrand Goldfields consist of four underground mining basins – Far Western, Western, Central and Eastern – defined in terms of hydrological connectivity below surface. The Far Western Basin, centred on Carletonville, still has deep underground mining taking place, so it is being actively dewatered. The other three have flooded so they were the focal points of this study. Environmental critical level (ECL) is the height (in metres above mean sea level - mamsl) to which the water can rise vertically in the abandoned void before

Mining Basin

Lowest flow of AMD (Ml/d)

Highest flow of AMD (Ml/d)

TDS noted in the DWS report (ppm)

Salts load under low flow (kg/d)

Salts load under high flow (kg/d)

Western Central Eastern

27 34 38

35 84

5388 3888 4248

145,476 132,192 161,424 439,092

188,580 326,592 467,280 982,452

110

TOTAL SALTS LOAD (KG/D

Source: Calculated from Table 1

terms this means over 400 tons a day during drought, and almost 1,000 tons a day during floods. Think of a ten-ton truck in convoy carrying salt down a highway. During drought, this convoy would be 40 trucks long, but in times of abundance it would be 100 trucks long. This convoy would deliver its load every day for as long as those flow conditions persisted. This triggered a technical study within the DWA designed to quantify the salinity status of the Vaal River system. The finding of that report is summarised in Figure 1. The river has a number of gauging stations starting with VS1 (in the headwaters) and ending with VS20 where it enters the Orange River in the vicinity of Douglas. The data-set from each of these gauging stations

TABLE 1 Summary of Data Presented in the AMD Focus Group Meeting on 7 September 2012 by the Department of Water Affairs Technical Team

Mining Basin

Suggested ECL (mamsl)

ECL proposed by TCTA (mamsl)

Recorded flow of AMD (Ml/d)

TDS noted in the DWS report (ppm)

TDS noted in the TCTA report (ppm)

Western Central Eastern

1600 1520 1470

1550 1467 1280

27-35 34-84

5388 3888 4248

7174 7700 5500

38-110

Figure 1: The Vaal Water Management Area showing the gauging stations and salinity distributed along the entire reach of the river. (Source: DWA Vaal Salinity Study, 2006).

Source: Feasibility Study for a Long-Term Solution to Address the Acid Mine Drainage Associated with the East, Central and West Rand Underground Mining. Bains, 7 September, 2012, Department of Water Affairs.

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19 | African Wildlife & Environment | 65 (2017)