GEO-6 Regional Assessment for Africa


phosphorus for future years (2000-2050) (Yasin et al. 2010) . This increases the risk of eutrophication in rivers, which can pose a threat to environmental and human health, affect tourism and lead to loss of livelihoods.


In addition to threats to water quality such as sedimentation, eutrophication and acidification of surface waters, climate change, the decommissioning and removal of dams from waterways, the discharge of chemicals into surface waters, and the identification of new and emerging pathogens pose challenges to maintaining water quality (UNEP/GEMS 2008). Few dams have been decommissioned in Africa, including the Wiken Weeg in the Kruger National Park in South Africa (Wray 2016). The removal of dams, which act as sinks for pollutants and silt, increases pollution loads downstream. However, the increase of dams in Africa both for water supply and energy is beneficial. The quality of freshwater from rivers is also affected by mine-water discharges containing toxic chemicals, though in the West Rand gold field of South Africa, for example, the discharge of acid mine water can, after expensive treatment, help to ensure the return of relatively clean water to the environment. At the same time, the direct flow of untreated mine water through the streams and rivers into the Hartbeespoort Dam may be having a negative impact on irrigation water owing to the concentration of toxic chemicals (Abiye 2014; Abiye et al. 2015). Environmental


contaminants such as the highly persistent organochlorine pesticides (OCPs) which are used in industry and agriculture, especially have deleterious effects on aquatic ecosystems and organisms, as well as bio-accumulate in the fatty tissues of organisms. In Zimbabwe, for example, the use of DDT (dichlorodiphenyltrichloroethane) for control of malaria mosquitoes and tsetse flies was responsible for the high levels found in the Lake Kariba ecosystem (Berg 1995) and accumulated levels in human breast milk (Chikuni et al. 1997)


Due to its hidden nature within rock interstices and fractures, groundwater is less known to consumers, making uncontrolled land-use activities more likely to deteriorate its quality. Shallow groundwater is compromised by poor sanitation through the use of pit latrines. In the Sorou Valley in Burkina Faso, for example, shallow wells that are important local sources of drinking water are highly polluted with coliform levels of 1 x 104 cfu/100 ml, compared to WHO standards of 0 cfu/100 ml (Boubacar et al. 2013). In south- east Botswana, the government is working on the water quality, which deteriorated due to poor sanitation, to make it potable. Naturally high fluoride content, such as in the East African Rift �alley groundwater, makes the water unfit for consumption. In addition, large-scale irrigation and industrial and mining pollution also play a significant role in making groundwater unfit for use by consumers. For example,


West Rand acid mine discharge, South Africa Credit: Tamiru Abiye


60


Mine water treatment facility, West Rand, South Africa Credit: Tamiru Abiye

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