Assessing alluvial mining effects on physico-chemical properties at premier Mawoyo bridge along Mutare river, Zimbabwe

Abstract

The effect of alluvial mining on physicochemical water quality of Mutare River along the corridor of Premier Mawoyo in Mutasa District in Manicaland Province in Zimbabwe was assessed in this investigation. There was no empirical data available for this site before this study, although there is a great deal of artisanal gold mining occurring along the river. The design used was quantitative cross-sectional comparative, where water samples were taken simultaneously from three strategically located sites; an upstream reference site (C1), an active mining site (M1), and a downstream monitoring site (C2). The analysis was performed by the Environmental Management Agency Analytical Laboratory that is accredited by the South African Department of Environmental Affairs and Sustainable Development (SADCAS) (Certificate Ref 261254-300, March 2026). Key findings show that concentrations of manganese at the mining site and the downstream site were 5.5 and 7.1 times above the EMA SI 6/2007, respectively, and the highest indication of the impact of the mining activities. The electrical conductivity at the upstream site was 167% higher than the downstream site. Three stations had dissolved oxygen saturation levels below the 75% criterion for dissolved oxygen, reflecting widespread oxygen stress throughout the study reach. It was also found that there was a large, natural organic and iron load at the reference site upsteam of the mine, unrelated to the mining operations. The null hypotheses were rejected. The study finds that alluvial mining negatively impacts the water quality of the Mutare River and that the downstream site is the site with the greatest potential for public health risk to communities that rely on the river for their water supply.