MORPHOMETRIC AND HYDROLOGICAL ANALYSIS OF THE NIAOULE SUB-WATERSHED (GAMBIA BASIN) USING GIS TECHNIQUES

Abstract

The growing demand and competition from the domestic, industrial and agricultural sectors for water have reached their limit. On land, drainage basins, watersheds and sub-basins are ideal hydrologic units for water resource conservation planning. The development of watersheds remains fundamentally for soil and water conservation in order to respond to different concerns. From this perspective, recourse to GIS techniques and remote sensing are useful for analyzing the morphometric properties of surface water reception basins. Morphometric aspects such as linear, relief and surface aspects of the Niaoulé sub-watershed located in the continental reach of The Gambia were analyzed using spatial tools and the arc-hydro tool in Arcgis. 10.5. The bifurcation ratio (3 to 5) indicates a basin with a reasonably homogeneous geology and without structural disturbances, and a young topography with a lower degree of drainage integration. This watershed has a less elongated shape with low relief, a gentle slope, coarse-type drainage, low propensity for soil erosion, a very moderate drainage texture, a permeable subsoil and a less dense vegetable cover. The techniques used in the study and the results are useful for planning and monitoring sub-watersheds for sustainable development.