Detecting changes in surface water extent of the Weija dam, Accra, Ghana using MNDWI indices from Landsat satellite imagery

This study evaluates changes in spatial extent of the Weija Dam in Accra, Ghana, which provides potable water to about 80% of the city’s 5 million residents, from 2011 to 2021. Landsat imagery and MNDWI algorithm were used to analyse changes in the dam’s surface area, while in-depth interviews assessed primary knowledge of causes and effects of these changes. Results show the dam had retreated approximately 19.668 sq km in 2011, a 48% reduction from its initial construction size in 1978. The surface area increased by 1.7% in 2013 but receded by 1.5 sq km in 2017 and a further 0.4 sq km in 2021. Interviews with participants revealed their concerns over the viability of the dam and their livelihoods were mostly caused by farmer encroachment, urbanisation, and siltation. The study recommends afforestation, flood control infrastructure, and community participation in dam management to increase the Weija Dam’s resilience and sustainability.