An investigation of the natural and human induced impacts on the Umdloti Catchment.

Abstract

The Umdloti River is relatively small but very important system that is located northeast of central Durban. This river flows pass the coastal town of Verulam and finally into an open/closed estuary, the La Mercy estuary. This fluvial system has a concrete gravity dam that is built in the upper reaches, the Hazelmere Dam, which supplies water to the north local council and surrounding districts under the supervision of Umgeni Water. The river is characterized by human activities, especially urbanisation and industrialization in the middle reaches and intensive agriculture (vegetables, sugar cane and banana plantations) along the catchment. The influence of anthropogenic factors within this catchment results from the dam construction, informal settlements, both commercial and subsistence agriculture, intensive industrial activity, accelerated urban developments, and recreational uses. Consequently there has been considerable concern regarding the impacts of these factors together with natural influences on the water quality and health status of this fluvial system. In this study water samples were taken and analysed for the following variables: nitrites; nitrates; ammonia; pH; Escherichia coli; sulphate; phosphate; total dissolved solids; chemical oxygen demand; biological oxygen demand; calcium and magnesium. The results indicate that the middle and the lower reaches of the Umdloti River are most impacted. Further, results from a questionnaire survey indicate that natural and human induced impacts have impacted negatively on the health status of the Umdloti River. The questionnaire survey also revealed that respondents benefited positively from the construction of the dam whilst the expropriation of land for the construction of the dam itself created much resentment to the prior land owners. The water quality data and the questionnaire analysis indicate overall natural and human induced impacts have had negative effects on the Umdloti River and the La Mercy estuary. It is necessary that local municipal authorities introduce corrective catchment management practices (outlined in the final chapter of the study) to enhance the water quality and health status of the river.