Hydraulic Audit and Techno-economic Comparison of Photovoltaic and Diesel Pumping for Drip Irrigation in the Maradi Valley, Niger

Aims: To audit an analytically sized, battery-backed photovoltaic (PV) drip-irrigation design for 1 ha in relation to borehole hydraulics and documented costs, and to compare it with direct-coupled PV and diesel pumping. Study Design: A design audit and numerical simulation study without field measurements. Place and Duration of Study: Djirataoua irrigation perimeter, Maradi, Niger (13.41° N, 7.14° E); reference design of January 2026, analysed in 2026. Methodology: An hourly model coupled FAO-56 crop water demand, PV output, a variable-speed submersible pump and tank and battery balances. Options were compared by the levelised cost of water (LCOW) and volumetric coverage, with Monte Carlo, Sobol and multi-objective analyses. The model was checked against the original PVsyst outputs but not validated with field data. Results: The main error was hydraulic: the design flow (23 m³ h⁻¹) was more than three times the borehole yield (7 m³ h⁻¹), the head was underestimated (20 instead of 25.4 m) and pump power was overestimated nearly threefold. A direct-coupled 3 kWp array with a 50 m³ tank met about 98 % of the seasonal demand; the January–February shortfall was set by the borehole, not by irradiation. At datasheet-based prices, direct PV, battery-backed PV and diesel cost 194, 201 and 190 FCFA m⁻³ (West African CFA franc): the battery did not reduce costs in the tested configurations, and solar was cheaper than diesel in about half of the Monte Carlo runs, depending mainly on the pump-set price. The reported internal rate of return (6.15) was an annuity factor. Conclusion: Such systems should be sized from a pumping test and the peak-day demand. The solar–diesel choice depends more on local pump-set prices than on sunshine, and groundwater sustainability must be assessed before any extension.