Contribution of GIS to Hydromorphometric Characterization of the Nkoup Watershed (Nun Plain-Cameroon)

Abstract

The Nkoup watershed (10°35’-10°47’E and 5°27’-5°42’N) is a volcanic zone situated in Nun Plain West Cameroon. The high fertility of the soils makes it a strategic agropastoral area where water resources are heavily exploited and used for several purposes. Due to human activities, soils and water resources are deteriorating, giving birth to water pollution and hydromorphological hazards. This work aims to determine the hydromorphometric parameters of the Nkoup watershed so that the data obtained help in the sustainable management of water resources and conservation of soil. To achieve this aim, various data were collected from DEM dataset derived from SRTM and processed in specialized software (QGIS and ArGIS). The simplified hydrological balance was calculated using the upstream approach. The Nkoup watershed has: Axial length Lax = 25.8 km, Axial Width Wax = 11.1 km, Perimeter P = 132.6 km, Area A = 173.7 km2 , Average Altitude Ha = 1726.3 m, Compactness Index Icomp = 2.8, Relief ratio Rr = 3.9 m/km, Circularity ratio Rc = 0.1, Elongation ratio R = 0.1, Drainage texture ratio Rt = 0.6, Drainage density Dd = 0.5 km/km2 . Stream Frequency Fs = 0.4, Channel Sinuosity Index CSI = 0.8, Stream gradient Sg = 0.6 and global slope Index Ig = 6.8 m/km. The specific height Difference Ds = 89.4 m shows moderate relief. The precipitation and evapotranspiration are unevenly distributed. With P = 187.7 mm/an, ETP = 953.4 mm/an, Q = 4.2 m3 /s, R = 762.5 mm/an, ETR = 832.3 mm/an and I = 282.9 mm/an. The Nkoup, 36.9 km long, has a sinuous aspect due to the low slope and the high CSI. The piezometric levels vary according to the seasons and the groundwater flow follows the N-S direction as surface flow.