Assessment of the impacts of agricultural activities on surface water and groundwater quality: a case study in the Brits area, North-West Province, South Africa

Abstract

The growing demand for food, driven by population growth, has resulted in the intensification of agricultural practices. To meet the demands, farmers have increased their use of pesticides and fertilisers to enhance food production. This has adverse effects on ecosystems, particularly aquatic ecosystems. In recent years, the impact of agricultural activities on water quality has received limited attention, particularly in South Africa. This study aims to investigate the effects of agricultural activities such as irrigation, pesticide application, and fertiliser use on groundwater and surface water quality in the Brits area of the North West Province. Twenty samples were collected, comprising thirteen groundwater samples, five samples along the Crocodile River and two samples from Hartbeespoort Dam and Roodekoptjes Dam. Prescribed sampling procedures were followed, and pH, temperature, and electrical conductivity were recorded on-site. Samples were analysed for Ca2+, Na+, Mg2+, K+, Cl-, SO42-, NO3-, PO43-, CO32-and HCO3-concentrations. These concentrations were used to evaluate irrigation suitability using methods such as SAR, %Na, Pl, MAR, and RSC. Chlorophyll-a was also measured in water samples. Most parameter concentrations fell within the permissible drinking water limits defined by the World Health Organisation and South African Water Quality Standards. Chlorophyll-a levels were significantly lower in groundwater but elevated in surface water samples, Roodekoptjes Dam recording the highest concentration of 25 µg/L, indicating the influence of agricultural runoff. The pesticide residues were below the detection limit in all the samples. The study found that, in addition to agricultural contributions to nutrient enrichment, wastewater and sewage spillages play a significant role. The presence of nutrients, pesticides, and chlorophyll-a in water indicates agriculture-related contamination, which poses risks to aquatic ecosystems and public health and necessitates appropriate remedial measures.