Correlation of water quality with farming activities : hydrochemical characteristics of the Bonsma Dam, KwaZulu-Natal

Abstract

Pressure to increase productivity of agricultural systems in order to meet domestic and international demand has resulted in the intensification of agriculture, exploitation of more land and greater reliance on pesticides, fertilisers, and imported animal feedstuff. Sources of pollutants from agricultural systems include livestock grazing, nitrates and phosphates in fertilisers, metals, pathogens, sediments and pesticides. Excess Nitrogen and phosphates accelerate algal production in receiving surface water, resulting in a variety of problems including fish kills and reduced recreational activities. To investigate the impact of farming activities (mainly dairy farming) on water quality, water samples were collected from the Bonsma Dam in KwaZulu-Natal and analysed for hydrochemical variables. The study showed that the concentrations of most of the metals, TDS as well as the pH and electrical conductivity values, met the water quality requirements for domestic, agricultural, livestock and aquatic ecosystem uses. Of concern were nitrates, chloride, aluminium and iron as they exceeded the guidelines set by the Department of Water Affairs and Forestry (DWAF) (1996) for irrigation and aquatic ecosystem uses. The iron and aluminium content of the dam water also did not meet the requirements for domestic use. Metals such as iron and aluminium could be detrimental to the health of humans and animals when they are present in excessive quantities.