Decision Support System Design for Water Resource Allocation in Kebbi State Irrigation Schemes

Water resource allocation among competing agricultural users in Kebbi State, North West Nigeria, is a technically complex and politically contested process, particularly within the Kainji and Dabmo irrigation schemes where over 40,000 smallholder farmers depend on controlled water releases from the Kainji reservoir. This study designs a mathematical decision support system for seasonal water allocation combining linear programming optimisation with a multi-objective framework that balances agricultural productivity, equity of access, and reservoir level sustainability. Hydrological data on reservoir inflows, evaporation losses, and downstream environmental flow requirements are obtained from the Niger River Basin Development Authority. Crop water requirement models for rice, sugarcane, and vegetables are parameterised using the FAO Penman-Monteith method applied to local meteorological data from Birnin Kebbi. The multi-objective programming model is solved using the weighted sum method with stakeholder-derived weights for each objective, and the Pareto-efficient solution frontier is mapped. Results indicate that a 15 percent reduction in rice allocation accompanied by intensification of vegetable cultivation increases total scheme revenue by 22 percent while reducing reservoir drawdown risk significantly. Sensitivity analysis shows that reservoir inflow uncertainty dominates allocation outcome risk in low-rainfall years. Keywords: water resource allocation, decision support system, Kebbi State, multi-objective programming, irrigation.