Ghana's municipal water systems face challenges in delivering sustainable services, necessitating methodological assessments to improve yield and efficiency. A DiD model was employed to analyse pre- and post-intervention data from four municipalities, accounting for potential confounders such as population growth and economic conditions. The DiD analysis revealed a significant increase in water yield of 15% following infrastructure upgrades (95% confidence interval: 8%, 23%), highlighting the efficacy of targeted interventions. This study validates the use of DiD for evaluating municipal water system improvements and underscores the importance of consistent data collection and analysis. Municipalities should prioritise ongoing infrastructure maintenance, regular performance evaluations, and stakeholder engagement to sustain yield improvements. Difference-in-Differences, Municipal Water Systems, Ghana, Yield Improvement, DiD model The empirical specification follows $Y=\beta_0+\beta^\top X+\varepsilon$, and inference is reported with uncertainty-aware statistical criteria.