{ "background": "The reliability of water treatment systems is a critical infrastructure challenge, with significant implications for public health and economic development. Inadequate performance of these systems remains a persistent policy concern, necessitating robust analytical tools for diagnosis and intervention.", "purpose and objectives": "This policy analysis article aims to develop and apply a quasi-experimental econometric model to evaluate the causal impact of specific national policy interventions on the operational reliability of water treatment facilities. It seeks to identify measurable performance gaps and inform future infrastructure investment strategies.", "methodology": "A difference-in-differences (DiD) model is employed, leveraging panel data from treatment plants across multiple municipalities. The core specification is $Y{it} = \\alpha + \\beta (Treati \\times Postt) + \\gamma X{it} + \\deltai + \\lambdat + \\epsilon{it}$, where $Y{it}$ is a reliability index. Inference is based on cluster-robust standard errors at the municipal level.", "findings": "Preliminary model diagnostics indicate a statistically significant negative treatment effect, with the policy intervention associated with an approximate 15-percentage-point reduction in system reliability scores compared to control groups. The parallel trends assumption holds pre-intervention, supporting the model's validity.", "conclusion": "The applied DiD framework provides a rigorous method for policy diagnostics in civil engineering systems, moving beyond descriptive analysis to causal attribution. The findings suggest that the evaluated policy mechanism inadvertently compromised system robustness.", "recommendations": "Policy formulation must integrate real-time reliability metrics and pre-implementation modelling. A shift towards outcome-based regulation, rather than input-focused compliance, is advised. Future infrastructure programmes should mandate pilot studies with control groups.", "key words": "infrastructure policy, causal inference, quasi-experimental design, water treatment, system reliability, econometric modelling", "contribution statement": "This article provides a novel application of the difference-in-differences methodology to engineering system performance in a policy context, generating a diagnostic