Remotely Sensed Assessment of Mining Severity Within Buffer Zones of Osun River: Implications for Drinking Water Quality, Biodiversity Protection, and Status as UNESCO World Heritage Site

Osun River, a UNESCO heritage site is currently under threat to unregulated mining activity along its course. Through remote sensing techniques, this study aimed to evaluate mining severity (number and size of mine pits) which was acquired and used to quantify landscape changes and degradation in water quality (turbidity) along the river. Studies were carried out using data for years 2020-2022 covering 2-km and 5-km buffer areas of the river's watershed. High-resolution Google Earth imagery and Landsat 8 imagery (OLI) were used for land-use land-cover assessment and computation of the Normalized Difference Water Index (NDWI) respectively. The mining severity assessment for 2022 revealed a total of 32 mining pits within the 5-km buffer zone, where 21 mining pits (65.63%) of the total mining activities occurred within the 2-km buffer zone. The severity assessment in terms of both the number of mines and the land area covered revealed an extensive physical mining activity, with severe impacts on surface water quality. The predominantly irregular shapes of the mine pits, indicated by the mean perimeter-to-area ratio ((X) over bar =0.22), linear regression (y = 0.1351x + 0.6102), and coefficient of determination (R-2=0.88), portend challenges for post-mining reclamation, including erosion control and terrain stabilization. The declining trend in the upper limit NDWI values over the 3 years, 2020, 2021, and 2022 (0.053, 0.017, and -0.084476 respectively), indicates a significant reduction in water quality, plausibly associated with the heightened mining activity within the 2-km buffer areas of the river. The escalating habitat degradation and imminent effects on drinking water quality and biodiversity health underscore the pressing implications of unchecked mining, eroding the ecological and cultural significance of the Osun-Oshogbo Sacred Grove, a UNESCO World Heritage Site. Urgent governmental action is crucial to enforce mining regulations, curbing these threats, and preserving the site's ecological and cultural importance.