Anthropogenic impact assessment on the water quality of Umhlathuze River in KwaZulu Natal Province, South Africa

Umhlathuze River and its three main tributaries experiences various anthropogenic activities including agriculture, urbanization and industrialization before forming an estuary with the Indian ocean. The current study assessed the potential impact of these anthropogenic activities over a 12-months period in 2023/4. The study found that elementary levels were mostly within the permissible limits along Umhlathuze River, but the impact of anthropogenic activities along its tributaries was evident. Chlorides ranged between 400 and 655 mg L^-1 along the Mholweni tributary during the rainy season while Na, Mg and Ca were also consistently above permissible limits along Mhloweni and Ntambanana tributaries. Among non-toxic trace elements, only Fe exceeded its health-based precautional value during the rainy season for all sites. Trace toxic metal levels were also within permissible limits. Hg was only detected along the tributaries in the 0.017-0.399 µg L^-1 range. The source of elevated levels of parameters along the tributaries was linked to quarry and agricultural activities, the wastewater effluents and urban runoff. The WQI values were in the 10.7-36.1 range implying the river water could be classified as good to excellent. The main river water was also found to be suitable for irrigation purposes, but water from the three tributaries was unsuitable with SAR values of 29.5-76.3. A health risk assessment identified that the river water was safe for adults but infants and children were more likely to develop non-carcinogenic effects with HI values of 1.07-3.28. The ILCR values ranged between 1.20 and 9.93 indicating that consumption of unprocessed water from Umhlathuze and its tributaries will result in carcinogenic effects over one's lifetime with infants and children affected most.