Assessment of Environmental Impacts of Large-Scale Irrigation Projects in Jigawa State

Large-scale irrigation development in Nigeria's semi-arid North West zone has been promoted as a pathway to food security and agricultural commercialisation, yet the environmental impacts of these schemes including soil salinisation, waterlogging, downstream flow reduction, and wetland disruption have received insufficient professional assessment. This study assesses the environmental impacts of large-scale irrigation projects in Jigawa State, focusing on two operational irrigation schemes developed under the Hadejia-Jama'are River Basin Development Authority. Environmental monitoring data covering soil salinity, drainage water quality, and downstream river flow records were obtained from the scheme management authority and supplemented with field measurements at 30 monitoring points within and downstream of both schemes. Satellite-derived soil moisture and vegetation condition indices were analysed to detect salinisation and waterlogging patterns. Structured interviews with 120 farming households on-scheme and 80 households in downstream floodplain communities documented perceived changes in land productivity and water availability. Findings indicate incipient salinisation affecting approximately 14 percent of surveyed on-scheme plots after more than fifteen years of irrigation, concentrated in low-lying areas with shallow water tables. Downstream communities report significant reductions in floodplain inundation extent and duration, affecting recession agriculture productivity and Hadejia-Nguru wetland ecosystem services. Drainage return flow quality is degraded by elevated salt and agrichemical residue loads. Recommendations focus on improved on-farm drainage management, irrigation scheduling optimisation, downstream environmental flow allocation, and establishment of independent environmental monitoring. Keywords: irrigation impacts, soil salinisation, Jigawa State, environmental monitoring, downstream hydrology.