Performance Assessment and Prospective Scenario Analysis of the Drinking Water Supply System in the Urban Commune of Diffa, Niger

This study assesses the performance of the drinking-water supply system in the Urban Commune of Diffa, Niger, and develops a prospective scenario analysis to 2040. It evaluates water demand, service coverage, production, distribution, billing, and selected network-performance indicators using documentary review, field observations, and interviews with water-service staff. The system comprises a mixed distribution network of 177.14 km, supplied by 12 boreholes and a 500 m³ storage reservoir, with 6,494 subscribers. Estimated water demand increased from 5,923.80 m³/day in 2019 to 6,983.52 m³/day in 2023, while population access was 54.5% in 2023. For January–June 2023, primary efficiency ranged from 76% to 96%, and the distribution-to-billing gap ranged from approximately 4% to 24%. The weighted production-to-billing gap over the six months was 22.39%. A prospective model using a 4.2% annual population-growth rate indicates that demand could reach approximately 14,055 m³/day by 2040. Three scenarios were evaluated: (i) a trend scenario maintaining the current overall efficiency of 77.61%; (ii) an improvement scenario progressively reaching 90% efficiency by 2040; and (iii) an optimal scenario combining 95% efficiency with production-capacity expansion and phased network extension. By 2040, the required production is estimated at approximately 18,110, 15,617, and 14,795 m³/day under the three scenarios, respectively. Diffa should pursue efficiency improvements and infrastructure investment together to improve the reliability and sustainability of drinking water services.