TITLE:
Infiltrability Variations on Surface Features of Sahelian Soils around Niamey (Southwestern Niger)
AUTHORS:
Harouna Amadou Harouna, Amadou Abdourhamane Toure, Moussa Boubacar Moussa, Manuela Grippa, Salifou Noma Adamou, Bouba Hassane, Issoufou Ide
KEYWORDS:
Surface Features, Hydraulic Conductivity, Soils, Niamey, Sahel
JOURNAL NAME:
Journal of Geoscience and Environment Protection,
Vol.13 No.8,
August
29,
2025
ABSTRACT: The Sahel is confronting hydrological modifications resulting from changes in surface features and soil degradation. Efficient soil management requires characterization of the hydrodynamics of surface features, which are highly diversified. The aim of this study was to assess the hydraulic conductivity of encrusted surfaces, undegraded surfaces, sown surfaces, walking paths of irrigated perimeters, and the bottoms of koris. These surface features are widespread in the central Sahel and in the study site, which is the complex of lakes on the eastern-northeastern periphery of the city of Niamey. The approach was based on measuring hydraulic conductivity using the BEST method and determining the physical parameters of the soils in the various surface features. In all the surface features analyzed, the soils were composed of at least 95% sand, with a very low fine clay-loam fraction, often well below 5%. Higher values of the very fine to fine sands fraction and of the clay-loam fraction tend to reduce hydraulic conductivity. On the contrary, the latter increases with increasing soil density, despite its low variability (1.31 - 1.49 g·m−3). Hydraulic conductivity is highest in the koris (4.6 × 10−2 mm·s−1 ± 4.6 × 10−2) and lowest (9.7 × 10−4 mm·s−1 ± 5.1 × 10−4) on the crusted surfaces above the plateaus. With rainfall intensities varying between 1.39 × 10−5 and 0.25 mm·s−1 in the area, almost 90% of the rainfall that falls on the plateaus runs off, causing severe erosion on the glacis. To combat this erosion, bench-type devices are built to store water on the plateau. Given the very low infiltrability of plateau soils, it is advisable to use soil management that slows runoff instead of that which stores water, which makes it prone to evaporation.