Land use/land cover dynamics using landsat data in a gold mining basin-the Ankobra, Ghana

Abstract

The Ankobra River basin, which forms part of the Southern-Western River System of Ghana, has become a hub for both large and small-scale mining activities. Some of the activities of these mines threatens the sustainability of its resources in the basin. A study in the basin which focuses on changes in LULC patterns in the basin over the past years is therefore paramount to understand the changes that has taken place and its potential impact on resources in the basin. This study assessed the pattern of Land use/cover changes, and the possible drivers of change, in the basin. The study used multi-spectral Landsat images of 30 m resolution for the years 1991, 2002, 2008 and 2016. The Semi-Automatic Classification Plugin (SCP) in QGIS was used for atmospheric correction, image classification using the spectral angle mapping algorithm, and post processing. The overall difference between the reference and the classified map of 2016 was 5.5% with the overall quantity, exchange and shift components as 1.5%, 3% and 1% respectively. Findings from the study show that, the Ankobra River basin has witnessed noticeable changes over the 25-year study period. Closed forest which occupied 40.4% of the total basin area in 1991 reduced drastically to 22.8% in 2016. The dominant LULC change patterns in the basin are from Closed Forest to Open Forest; Open Forest to Farmland, Settlement/Bare land and Mining Area; and the increase in surface area of Water consequently resulting from the increase in Mining Area. Mining activities, particularly illegal mining was identified to be the dominant driver of deforestation in the Ankobra Basin between the years 2008 and 2016 where mining activities in the basin sharply increased.