Evaluating economic and public health justifications for water safety plans: A cost-benefit and risk reduction perspective for Zimbabwe

Water Safety Plans (WSPs) are internationally endorsed frameworks for ensuring the safety and sustainability of drinking water through proactive risk management. In some countries such as Zimbabwe, however, implementation remains sporadic due to perceived financial and operational barriers. This study presents a comprehensive economic and public health evaluation of WSPs in both urban and rural settings using advanced decision-making metrics. A 10-year cost-benefit analysis (CBA) revealed Benefit-Cost Ratios (BCRs) of 34.8:1 (urban) and 57.0:1 (rural), with Internal Rates of Return (IRR) exceeding 55%. The intervention was estimated to avert approximately 37,970 DALYs averted over 10 years (21,710 urban and 16,260 rural), reflecting morbidity reductions but excluding mortality impacts, and a Cost-Effectiveness Ratio (CER) as low as $43.68 per DALY. The WSPs achieved disease Incidence Rate Reductions (IRR%) of ∼42% (urban) and ∼61% (rural), with a break-even point within the first year of deployment. Sensitivity analysis confirmed that these results remained robust under variations in discount rate, incidence reduction and cost assumptions. Environmental benefits, including reductions in biochemical oxygen demand, chemical oxygen demand and improved compliance with Word Health Organization microbial standards, further enhance the return on investment.