Spatiotemporal analysis of the wetland dynamics using geospatial techniques: case of Gojeb River sub-basin, Ethiopia.

Abstract

Wetlands are productive ecosystems that mitigate floods, recharge groundwater, filter nutrients, regulate climate, and support biodiversity. However, these ecosystems are increasingly threatened by agricultural expansion and settlement. This study evaluated wetland dynamics in Ethiopia's Gojeb River sub-basin using field observations, socio-economic surveys, and remote sensing data. Land use/land cover (LULC), Normalized Difference Water Index (NDWI), and Normalized Difference Vegetation Index (NDVI) were analyzed using Landsat 7 ETM + (2000), Landsat 5 TM (2011), and Landsat 8 OLI/TIRS (2024). Supervised LULC classification was performed using a maximum likelihood technique in ERDAS software. LULC change analysis revealed declining vegetation and wetland by 25.2 and 1.6 km²/year, while agricultural land and built-up areas increased by 43.4 and 2.9 km²/year, respectively. The decline in NDVI from 0.75 to 0.58 and NDWI from 0.66 to 0.32 between 2000 and 2024 indicates severe vegetation and wetland loss in Gojeb. Despite the crucial ecological and economic benefits of wetlands, their declining trends underscore the need for regular monitoring, for which geospatial technology has been shown to be an effective tool. Expanding farm areas, population growth and settlement, fuel wood and timber exploitation, and poor management systems were the key drivers of change dynamics. The findings highlight the serious effects of human activity and urge for more strict conservation policies to preserve biodiversity and guarantee the sustainability of the ecosystem. Effective policies that support integrated agroforestry and wetland conservation strategies such as buffering and zoning, are necessary to counteract ecosystem degradation and improve socio-ecological resilience.