Abstract
Water quality monitoring in the Olifants River catchment, Mpumalanga, is evaluated using river water dissolved sulphate levels, one of the best indicators of pollution related to acid mine drainage. Assessment of long-term water quality records shows that monitoring has not been carried out systematically. In that it fails one of the most fundamental criteria of good environmental monitoring practices. At some monitoring stations sampling frequency has been scaled down from approximately weekly to monthly intervals over time, despite evidence for increasing and problematic levels of pollution. At the Loskop Dam dissolved sulphate levels have increased more than 7-fold since the 1970s evidently due to increasing levels of pollution within the Little Olifants River catchment. At 4 of the 7 long-term monitoring stations river water sulphate levels exceed the 100 mg/l threshold value for aquatic ecosystem health most of the time for the duration of the record, and all of the time since about 2001. At these stations river water sulphate levels also exceed the 200 mg/l threshold for human consumption 27 to 45% of the time, for the duration of the long-term record. These observations necessitate more frequent and improved monitoring, not evidently reduced efforts. A major concern is the location of a recently re-opened copper mine outside Phalaborwa, just upstream from the confluence of the Ga-Selati River and the Olifants River. Levels of copper sulphate, highly toxic to aquatic species, should be urgently investigated as a probable cause of recent fish and crocodile deaths in the Kruger National Park. In river systems subject to intensive mining activity, such as the Olifants River, toxic constituents such as copper, arsenic, chrome-VI, etc., currently not routinely measured by the Department of Water Affairs (DWA) need to be included in monitoring efforts as a matter of urgency. This will require drastic improvements in current water quality monitoring efforts, including the acquisition of modern analytical instrumentation.
Highlights
The Olifants River in Mpumalanga is presently one of the most threatened river systems in South Africa (Van Vuuren, 2009; Ballance et al, 2001)
This study evaluates water quality monitoring in the Olifants River, based on
According to the South African Water Quality guidelines (DWAF, 1996a), the target water quality range (TWQR) for dissolved sulphate is below 200 mg/l for human consumption
Summary
The Olifants River in Mpumalanga is presently one of the most threatened river systems in South Africa (Van Vuuren, 2009; Ballance et al, 2001). The dissolved sulphate derives from the oxidation of metal sulphides such as pyrite, abundant in, for example, coalrich lithologies and precious metal-rich deposits This makes dissolved sulphate levels ideal for testing hypotheses such as that deteriorating water quality in the Olifants River is attributable to gold- and coal-mining activities in the upper catchment. Dissolved sulphate is relatively easy to measure, which ensures robust long-term data records These characteristics of river water sulphate all contribute to making it ideal for the detection of temporal and spatial differences in water quality related to acid mine drainage within a catchment such as the Olifants River. Sampling has been even more erratic at the Loskop Dam and Kruger National Park monitoring stations, which are currently being sampled at frequencies of monthly or less The latter 2 locations are most relevant to elucidating the increasing frequency of fish and crocodile deaths in the Olifants River system. N is the total number of measurement points in the data records
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