Living with eutrophication in South Africa: a review of realities and challenges

Abstract

The socio-economic well-being of South Africa is largely dependent on reservoir lakes. Contrastingly, the country lacks reservoir management skills and training, with a generation having passed since there was limited activity in this field. This review introduces two new, independent analyses which, using in-lake total phosphorus or satellite-measured chlorophyll-a, respectively, reveal that between 41% and 76% of total storage is eutrophic or hypertrophic. This is in stark contrast to a claimed 5% made by the responsible government agency (Department of Water and Sanitation). Data and information on the incidence and toxicity of cyanobacterial blooms are sparse, yet severe problems exist. There is a concentration of focus on water quantity, with absent parallel consideration of the additional limitations posed by poor water quality. The most seriously impacted reservoirs are located in the economic heartland of South Africa, which has an extant regional water quality crisis. The reasons behind the startling lack of attention to reservoir limnology, despite clear and long-standing warnings, are examined and placed in the perspective of an acknowledged and impending water crisis. It will take considerable time to up-skill South African limnologists to meet the needs highlighted by worsening reservoir water quality, and to offset the social and economic impacts that will transpire, if not timeously ameliorated. The responsible agency urgently needs to establish a reservoir-management programme that embraces remaining individual and institutional memory, integrates all available relevant knowledge and scientific findings, prioritises needs and acquires those skills and resources necessary to meet what is likely to become a crippling legacy of inaction.

rise and fall of dissolved phosphate in South African rivers

“…10 Increasing eutrophication in South African freshwater ecosystems is no exception to the global trend, and a number of publications have expressed concern at the ongoing impact of eutrophication on local water resources. 9,11,[12][13][14][15][16][17][18] While nutrient levels in many catchments may be low at times, trends show an increase with time in levels of nutrients in most catchments, most particularly in the case of phosphate. 9,19 Increased nutrient levels in South African rivers have been accompanied by increases in eutrophication of reservoirs in the country to the extent that, depending on estimates, half or more of the larger reservoirs in the country are eutrophic or hypertrophic.…”

“…9,19 Increased nutrient levels in South African rivers have been accompanied by increases in eutrophication of reservoirs in the country to the extent that, depending on estimates, half or more of the larger reservoirs in the country are eutrophic or hypertrophic. 12,13,17,18 This level of eutrophication has severe ecological and economic consequences, and concerns have been raised regarding the capacity in South Africa for managing the situation. 18 Despite a chemical water quality monitoring programme that monitors nutrients at hundreds of points across South Africa, there is relatively little published information on trends in nutrient levels with time.…”

“…12,13,17,18 This level of eutrophication has severe ecological and economic consequences, and concerns have been raised regarding the capacity in South Africa for managing the situation. 18 Despite a chemical water quality monitoring programme that monitors nutrients at hundreds of points across South Africa, there is relatively little published information on trends in nutrient levels with time. De Villiers and Thiart 9 looked at trends in nitrate/nitrite and phosphate at points low in major catchments over the full data record.…”

“…This greater Since the promulgation of the 1 mg P/L standard for discharged effluent, most of the eutrophication management in South Africa has focused on phosphorus concentration management. 12,18,20,21 Phosphate loading in South Africa has been associated with discharge of wastewater treatment works effluent 19,22,23 , urban run-off 24,25 , the use of phosphatecontaining detergents 12,18,26,27 , mining 28,29 and agricultural activity 30,31 .…”

“…Phosphorus loads from urban areas entering freshwater resources have particularly received considerable attention of late 18 because primary and secondary treatment of wastewater removes very little phosphate 32 , and because South African wastewater treatment works do not focus on phosphorus removal 18 . In addition, a significant portion of the phosphorus in domestic wastewater derives from phosphate-containing laundry detergents 26,27 which in many other countries have been banned or limited.…”