Hydro-Climatic Variability and Human Activities Impact on the Morphology of the Cavally River Bed, Western C？te d’Ivoire

The Cavally watershed is covered by a large forest area, where for decades there has been intense agricultural and mining activity (modern and traditional). Anthropogenic pressures and hydro climatic variability can significantly alter the hydrological response of the Cavally River watershed. The objective of this study is to assess the impact of hydro climatic variability and land-use dynamics on the availability of water resources in the Cavally River basin. To achieve this objective, two methodological approaches were used, a first approach was used to calculate the rainfall and hydrometric indices to determine the different hydro-climatic trends of the watershed. The second approach consists in analyzing the inter-annual morphological evolution of the bed of the Cavally River by using Landsat images from 1986s, 2011s and 2018s. The results of this study show that several successive years of drought were observed in the Cavally Basin from 1970 to 1980. Analysis of hydro-climatic trends showed that rainfall has declined, and the land use map analysis showed that the vegetation cover has been significantly degraded (Four common land use classes were finally mapped. They are represented by dense vegetation with 13.11%; degraded vegetation and crops with 72.04%; water with 4.73%; built areas and bare soils with 10.12%). About the evolution of the Cavally River bed, illegal gold miners could be the cause of the increase in the surface area of the water body located between the SMI and the Floleu village (Section 3 where the morphology of the Cavally River bed has increased considerably by 13.70% between 1986 and 2011 and by 55.93% between 2011 and 2018). Indeed, this area is frequented daily by gold miners who carry out their activities both in the minor bed and on the banks of the river.