Eutrophication of Inland Surface Waters in South Africa: An Overview

Abstract

Eutrophication of fresh waterbodies is a global phenomenon that is exacerbated by increases in agricultural activities, industrialization, and urbanization, all driven by the global increase in human population. This paper reviews the state of inland waterbodies in South Africa, identifying the major drivers of eutrophication and discussing how different sectors of the economy are negatively impacted by eutrophication. Data indicate that up to 76% of major water impoundments and approximately 70% of major river systems are eutrophic to hypereutrophic and experience protracted periods of cyanobacterial blooms, particularly in the summer months. Negative impacts of eutrophication on the agricultural sector, potable water supply and tourism are well documented and are becoming more explicit. Evidently, nutrient loading patterns into water bodies have changed and become more complex. Although wastewater treatment plants remain the major contributors of nutrient loads to most waterbodies, non-point sources including agricultural runoff, untreated sewage from leaking and overflowing sewer systems, as well as runoff from informal settlements, also make substantial contributions. As a result, the strategies employed to prevent eutrophication, including within-waterbody remediation programs have fallen short in reducing the trophic status of water impoundments and thus ameliorating the symptoms of eutrophication. Tailor-made, integrated management initiatives that target point source, non-point source, and internal nutrient loads are, therefore, required.