Assessment of Environmental Degradation in Irrigation Schemes of Sokoto-Rima Basin, North West Nigeria

Large-scale irrigation schemes in the Sokoto-Rima Basin have expanded agricultural production but are associated with secondary environmental problems including waterlogging, soil salinisation, and eutrophication of drainage channels. This study assessed the extent of environmental degradation in irrigation command areas of the Bakolori and Daberam schemes in North West Nigeria. Soil salinity and waterlogging extent were mapped using electrical conductivity measurements from a systematic soil sampling grid and satellite-based soil moisture indices. Drainage channel water quality was characterised for nutrients, pesticide residues, and biological oxygen demand. Canal lining integrity and drainage network function were evaluated through field assessment. Results showed that approximately 18 percent of the Bakolori command area exhibited moderate to severe soil salinisation, concentrated in flat poorly drained fields. Waterlogging affected an estimated 22 percent of the irrigable area during peak irrigation periods. Drainage channel water showed elevated nitrate and orthophosphate concentrations, consistent with fertiliser leaching. Pesticide residue screening detected traces of organophosphate compounds in 40 percent of drainage water samples. Canal lining deterioration was widespread, contributing to seepage losses and waterlogging of adjacent fields. The study recommends rehabilitation of drainage infrastructure, adoption of deficit irrigation scheduling to reduce percolation losses, and soil reclamation through gypsum application in severely salinised areas of both irrigation schemes. Keywords: irrigation, soil salinisation, waterlogging, Sokoto-Rima Basin, environmental degradation.