A Watershed Approach in Identifying Key Abiotic Ecosystem Drivers in Support of River Management: a Unique Case Study

Since the industrial revolution, the impact of effluents produced by human activities on ecosystems has been a major international environmental concern. This study was aimed at observing the changes in water and sediment qualities at a watershed level of two different river systems facing the same land use practices, but impacted to different degrees. Samples were collected at strategically selected sites within the mainstream of both rivers, the major tributaries draining into them, as well as a major impoundment in each system. A distinct difference between the two different rivers was observed. It was established that certain variables, for example pH, contributed to the differential water and sediment quality signatures in the upper Olifants and Mokolo rivers, having important considerations for the future management of both river ecosystems. Other abiotic factors, such as alkalinity and sulphate levels, were also found to be important. The tributaries were found to play an important role in the purification and/or pollution of the mainstream rivers. On the other hand, the present impoundments in the Mokolo River were observed to affect the water and sediment qualities downstream. Overall, through the use of comparative models, it was observed that the upper Olifants River was in a different state than the Mokolo River and the information from this study may aid in the future management of the Mokolo River to prevent a shift to an undesirable state.