Assessment of Spatio-Temporal Changes of Land Use and Land Cover over South-Western African Basins and Their Relations with Variations of Discharges

Abstract

West African basins play a vital role in the socio-economic development of the region. They are mostly trans-boundary and sources of different land use practices. This work attempts to assess the spatio-temporal land use and land cover changes over three South Western African basins (Volta, Mono and Sassandra basins) and their influence on discharge. The land use and land cover maps of each basin were developed for 1988, 2002 and 2016. The results show that all the studied basins present an increase in water bodies, built-up, agricultural land and a decline in vegetative areas. These increases in water bodies and land use are as a result of an increase in small reservoirs, of dugouts and of dam constructions. However, the decline in some vegetative clusters could be attributed to the demographic and socio-economic growth as expressed by the expansion of agriculture and urbanization. The basic statistical analysis of precipitation and discharge data reveals that the mean annual discharge varies much more than the total annual precipitation at the three basins. For instance, in the entire Volta basin, the annual precipitation coefficient of variation (CV) is 10% while the annual discharge CV of Nawuni, Saboba and Bui are 43.6%, 36.51% and 47.43%, respectively. In Mono basin, the annual precipitation CV is 11.5% while the Nangbeto and Athieme annual discharge CV are 37.15% and 46.60%, respectively. The annual precipitation CV in Sassandra basin is 7.64% while the annual discharge CV of Soubre and Dakpadou are 29.41% and 37%, respectively. The discharge varies at least three times much more than the precipitation in the studied basins. The same conclusion was found for all months except the driest months (December and January). We showed that this great variation in discharge is mainly due to land use and land cover changes. Beside the hydrological modification of the land use and land cover changes, the climate of the region as well as the water quality and availability and the hydropower generation may be impacted by these changes in land surfaces conditions. Therefore, these impacts should be further assessed to implement appropriate climate services and measures for a sustainable land use and water management.

Climate, Land Use and Land Cover Changes in the Bandama Basin (Côte D’Ivoire, West Africa) and Incidences on Hydropower Production of the Kossou Dam

“…The analysis of land cover changes in the basin between 1988 and 2016 reveals that water bodies and land use (built-up and agricultural land) have increased while the vegetative area (savanna, herbaceous savanna, forest and evergreen forest) has decreased. These results are in accordance with previous studies in the region [42,46,50]. The increase in water bodies is due the increase in the construction of small reservoirs, dugouts and dams within the basin.…”

Effects of hydroelectric dam construction on spatio-temporal changes of land use land cover in Bui National Park, Ghana

“…The water bodies increased significantly during the post-dam construction period, which can be attributed to the increase in the level of the reservoir created by the hydroelectric dam in the BNP, an observation that has been reported by other similar studies elsewhere (Obahoundje et al, 2018; Wiejaczka et al, 2017; Zhao et al, 2010).…”

“…The grassland decreased its cover from 2010-2020. Other researches (Chalise et al, 2019;Özüpekçe, 2019;Wiejaczka et al, 2017;Xu & Chi, 2019) This causes reduction in quality and quantity of forage as well as modifying vegetation and soil formation due to soil compaction (Obahoundje et al, 2018;Panthi et al, 2017;Sharma et al, 2019). In some cases, cattle herdsmen attempt to cause regeneration of fresh pasture by consciously setting fire to the vegetation resulting in uncontrolled destruction of vegetation (Sharma et al, 2019).…”

“…The Bui hydroelectric dam is found at the southern end of the BNP. The dam is a gravity, roller-compacted concrete type with a height of a 110 m above foundation and creating a reservoir of 12,350 million m 3 with a total surface area of 440 km 2 (Habia, 2009; Obahoundje et al, 2018).…”

Hydro-climatic and land use/cover changes in Nasia catchment of the White Volta basin in Ghana

“…Yet in this study, deforestation resulted in increased settlement and shrubland coverage, compared to croplands, signalling a reduction in farming activities in the basin. Excessive use of trees for charcoal and wood fires and uncontrolled bushfires are the main drivers of deforestation in sub-Saharan Africa (Obahoundje et al, 2018). Firewood or wood fuel accounts for 70% of sub-Saharan Africa total energy production, and due to the increase in population growth rate, and relative price changes of alternate energy sources for cooking, it is expected that the trend of using firewood will continue (Kebede et al, 2010).…”