Coupled Hydrological-Livelihood Modelling of Irrigation Water Allocation Trade-offs in the Hadejia-Nguru Wetlands System, North East Nigeria

The Hadejia-Nguru Wetlands constitute one of West Africa's most ecologically and economically important dryland wetland systems, yet upstream irrigation water abstractions progressively reduce annual flood pulses that sustain the wetland's ecological functions and the livelihoods of over one million dependent people. This doctoral research develops and applies a coupled hydrological-livelihood modelling framework to quantify water allocation trade-offs between upstream irrigation and downstream wetland-dependent livelihood systems in the Hadejia-Nguru Wetland system. The hydrological modelling component develops a calibrated Soil and Water Assessment Tool model for the entire Komadugu-Yobe catchment, incorporating current and projected future irrigation abstractions from the Kano River Irrigation Project and smaller schemes. Downstream wetland flood pulse dynamics are simulated under alternative allocation scenarios. The livelihood modelling component employs a computable livelihoods model estimating household welfare outcomes for eleven livelihood typologies in wetland communities under the hydrological scenarios. The coupled model system enables integrated assessment of allocation policy alternatives including environmental flow regimes, irrigated area constraints, and efficiency improvement investments. Findings indicate that each 10 percent reduction in upstream irrigation abstractions generates disproportionately large downstream livelihood benefits due to non-linear wetland productivity responses to flood pulse timing and extent. The study makes original contributions to coupled hydrological-social system modelling for dryland wetlands in Africa, provides a quantitative evidence base for Hadejia-Nguru Wetlands Ramsar site management, and informs the Komadugu-Yobe Water Charter review process. Recommendations address minimum environmental flow standards, irrigation efficiency investment prioritisation, and compensation mechanisms for irrigation constraint policies. Keywords: hydrological modelling, wetland livelihoods, Hadejia-Nguru, water allocation, Ramsar wetland.