Nutrient Loading from Agricultural Runoff into Hadejia Wetlands, Jigawa State

The Hadejia Wetlands in Jigawa State, North West Nigeria, constitute a globally recognised Ramsar site supporting exceptional biodiversity and the livelihoods of over a million people through flood recession agriculture, pastoralism, and fisheries. Intensification of irrigated farming upstream has substantially increased fertiliser-derived nutrient loads entering the wetland system, with potential consequences for eutrophication, aquatic biodiversity, and water supply safety. This study quantifies nutrient loading from agricultural runoff entering the Hadejia Wetlands during the 2023 to 2024 farming cycle. Monthly water samples from six inflowing channels and three wetland interior stations are analysed for total nitrogen, ammonium, nitrate, total phosphorus, and orthophosphate. Discharge measurements using a mechanical current meter and cross-sectional surveys enable nutrient flux calculations at each inflow point. Agricultural land use in the upper catchment is mapped using Sentinel-2 imagery, and a simple export coefficient model estimates the contribution of different land use types to observed nutrient loads. Statistical analysis relates nutrient concentrations to upstream discharge and seasonal growing patterns. Findings are expected to show elevated nitrogen and phosphorus inputs during post-harvest irrigation drainage periods from November to February, exceeding wetland self-purification capacity during low-water conditions. Recommendations include buffer strip implementation between farmland and wetland margins and revised fertiliser application guidelines for extension workers in Jigawa State. Keywords: nutrient loading, agricultural runoff, Hadejia Wetlands, Jigawa State, eutrophication