Browsing by Subject "Environmental Sciences"

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    Open Access
    Nutrient fluxes within the Berg River from 1976 to 2017, Western Cape, South Africa
    (2019) Molebatsi, Lemogang; Winter, Kevin
    Deterioration of freshwater systems due to eutrophication is increasingly a global concern because it puts stress on the already limited freshwater systems. Eutrophication is caused by elevated levels of nutrients in river systems primarily from poor land management whereby excess nutrients are discharged into fresh water bodies. It is exacerbated by factors such as human population growth, economic growth and climate change. The main aim of this study was to analyze the changes in the nutrient status of the Berg River since the 1970s and tendencies toward hypertrophic conditions. The Berg River is an important source of bulk water supply for both domestic and industrial purposes in the Western Province, South Africa. The study examined water quality data from the Department of Water and Sanitation’s Resource Quality Information Services for nine monitoring sites along the Berg River to determine the long-term trends. The data sets were analyzed using parametric statistics. The results show that nutrient levels in the Berg River are increasing at almost all the selected monitoring sites. The long term trend showed low mean values for both upstream and downstream with a peak nutrient levels observed along sections that were densely populated and extensively cultivated. Based on available total phosphorus data, all sites were classified as eutrophic except a monitoring site along the most populated and cultivated section of the Berg River which was permanently hypertrophic. Long-term mean values for total phosphorus exceed the recommended international guidelines for aquatic plant life. The long-term mean values of nitrate and nitrite also exceed the recommended guideline for aquatic plant life. Ortho-phospate mean values for the study showed that all sites experienced hypertrophic states at some stage during 1987 to 2017. Student t-test analyses confirm that nutrient concentration loads had increased in the past decade. The results confirm that anthrophogenic activities and climate change are two major drivers of change resulting in an increase in eutrophication. Therefore, serious attention should be paid to the role of anthrophogenic activites and climate change to mitigate the negative impact on freshwater systems.
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    Open Access
    Nutrient loading in the Vaal River over the past two decades
    (2019) Ntshalintshali, Pargeant; Winter, Kevin
    Nutrient loading is negatively affecting South Africa’s freshwater resources and ecosystems. Anthropogenic activities are the leading causes of continuous nutrient loading in the country’s water resources. This study examines the dynamics of nutrient loading in the Vaal River. The objectives are to explore nutrient loading in the Vaal River over the past two decades and to compare the differences between the two decades. Water quality data were obtained from the Department of Water and Sanitation (DWS) Water Resource Quality Information Services (RQIS) database. Elevated nutrients of NH4+, N03, P04 3- and chlorophyll-a were observed at selected sites at various times during the 20 year period under analysis. Nutrients concentration are elevated alongside agricultural and industrial activities, and urban areas. Student t-tests investigated the difference between the two decades and in most cases showed significant differences between these decades. The last decade showed elevated nutrient levels for N03, NH4+ and chlorophyll-a in most of the DWS monitoring sites. Only P04 3- at some sites showed a reduction from the previous decade. The study concludes that upper and middle sections of Vaal River are eutrophic and hypertrophic and a trend toward a permanent state of these conditions is likely without a long-term solution to address the problem of excessive nutrient loading entering the Vaal River system.