Analysis of Land Cover Changes in the Bonsa Catchment, Ankobra Basin, Ghana

Abstract

PBAG x01, 3209, Scottsville, Pietermaritzburg,Abstract. Multi-temporal land cover changes in the Bonsa catchment of the Ankobra Basin in Ghana were determined using four satellite images from 1986, 1991, 2002 and 2011. The results indicate that evergreen forest is the largest class occupying an area of 68% in 1986, 62% in 1991, 50% in 2002 and 51% in 2011 and during the past 26 years, the largest land cover change has been the conversion of evergreen and secondary forests to shrubs/farms, mining areas and settlements. During this period, mining areas increased over two-fold, while settlements and shrubs/farms increased more than three and four-fold, respectively. This resulted in increasing annual deforestation rate of 0.33% between 1986 and 1991, 0.70% between 1991 and 2002 and 2% between 2002 and 2011. The results suggests that the drivers of the land cover changes in the Bonsa catchment, are both local and global and include, international trade, local population growth, agriculture extensification and urbanization. The identified land cover changes have the potential to impact negatively on the hydrological regimes of the Bonsa River and the local communities by leading to flooding, soil erosion and the siltation and pollution of the river during peak seasons and the scarcity of water during dry seasons. Therefore, the maps and statistics generated can be applied to assess the impacts of the land use changes on the local hydrology and provide a better basis for future land use planning. Through these findings the importance of multi-temporal analysis of satellite imagery for planning in data poor regions is highlighted.

Assessing Impacts of Land Use Changes on the Hydrology of a Lowland Rainforest Catchment in Ghana, West Africa

“…The land use of the Bonsa catchment prior to the implementation of the economic liberalization programs of the Ghana government in the late 1980s and early 1990s was mainly evergreen forests, but currently (2011) only 51% of it remains [28]. Although the study shows a substantial alteration of the hydrology between the baseline (1991) and current (2011) land use (LU) scenarios, the seasonal patterns of the high and low flows have been maintained.…”

“…However, the current hydrological regime (i.e., 2011 land use scenario), shows significantly higher peak and dry season flows relative to the baseline flows. The higher flows in the current hydrological regime is because of deforestation and urbanization, as well as expansion in surface mines [28].…”

“…However, in the rainforest regions of the south, where the majority of West African population live, there remains a lack of knowledge on the hydrological impacts of land use changes at the local scale, despite land use changes being significant over the past three decades [1,28]. Previous land use change impact studies on hydrology in West Africa have been mainly undertaken in the semi-arid areas and the Sahel parts of the region [14,17,19,20,[23][24][25][26][27]29].…”

“…Mining areas have increased over twofold, while settlements and shrubs/farms increased more than three-and fourfold, respectively, leading to overall annual deforestation rates of 0.3% between 1986 and 1991, 0.7% between 1991 and 2002, and 2% between 2002 and 2011 [28]. It is also expected that in the near future, rates of land use changes may be substantially higher than the current rates.…”

Dynamics of Land Cover Changes and Delineation of Groundwater Recharge Potential Sites in the Aguanaval Aquifer, Zacatecas, Mexico

“…Due to the above details, it is important to recognize and understand land cover (biophysical attributes of the earth's surface) and land use (human purpose or intervention applied to these attributes) changes as the major ecological processes affecting and that are affected by the dynamic interaction of ecosystems (Ricca and Guagliardi, 2015) and in turn, the impact of the hydrological responses of a catchment by altering the partitioning of precipitation into different components of the hydrological cycle, such as interception, infiltration, runoff, evapotranspiration, and groundwater recharge rate (Aduah, 2015). Likewise, ecosystem services can be defined as the conditions, processes and components of the natural environment that provide tangible and intangible benefits for the maintenance and fulfillment of human life (Sherrouse et al, 2011).…”