Water safety plans (WSPs) represent a holistic risk assessment and management approach covering all steps in the water supply process from the catchment to the consumer. Since 2004, the World Health Organization (WHO) has formally recommended WSPs as a public health intervention to consistently ensure the safety of drinking water. These risk management programs apply to all water supplies in all countries, including small community supplies and large urban systems in both developed and developing settings. As of 2017, more than 90 countries had adopted various permutations of WSPs at different scales, ranging from limited-scale voluntary pilot programs to nationwide implementation mandated by legislative requirements. Tools to support WSP implementation include primary and supplemental manuals in multiple languages, training resources, assessment tools, and some country-specific guidelines and case studies.

Systems employing the WSP approach seek to incrementally improve water quality and security by reducing risks and increasing resilience over time. To maintain WSP effectiveness, water supply managers periodically update WSPs to integrate knowledge about prior, existing, and potential future risks. Effectively implemented WSPs may translate to positive health and other impacts. Impact evaluation has centered on a logic model developed by the Centers for Disease Control and Prevention (CDC) as well as WHO-refined indicators that compare water system performance to pre-WSP baseline conditions. Potential benefits of WSPs include improved cost efficiency, water quality, water conservation, regulatory compliance, operational performance, and disease reduction. Available research shows outcomes vary depending on site-specific context, and challenges remain in using WSPs to achieve lasting improvements in water safety. Future directions for WSP development include strengthening and sustaining capacity-building to achieve consistent application and quality, refining evaluation indicators to better reveal linked outcomes (including economic impacts), and incorporating social equity and climate change readiness.