Mapping five decades of the evolution and digital transformation of WASH tools for low-income and fragile contexts

This review synthesises more than five decades of Water, Sanitation, and Hygiene (WASH) tool evolution, from the analogue, hardware-centred instruments of the 1970s to contemporary digital platforms and early AI-enabled applications through 2025. Drawing on a semi-systematic search of academic, institutional, and grey literature, the paper maps major tools, their functions and digital maturity, across water supply, sanitation, hygiene, and solid waste management, with a focus on low-income and fragile contexts. Analysis reveals a progression from paper-based checklists and technical guides in the 1970s to structured monitoring and participatory planning instruments in the 1990s-2000s, followed by mobile-enabled and digital systems in recent years. Findings show that water-supply tools are comparatively mature and digitally advanced, sanitation tools remain the least digitally integrated and underrepresented, and solid waste management exhibits high functional diversity but uneven digital uptake. Since 2010, integrated instruments have emerged that link WASH with climate risk and public health; a small number of tools now incorporate predictive analytics and remote sensing, but AI and IoT applications remain nascent in resource-constrained and fragile contexts. The review identifies gaps in empirical evaluation, digital readiness, scalability, and governance alignment, and highlights factors that influence tool uptake-such as institutional embedding and donor support. The review informs developers and organizations on future innovation and global application of tools to accelerate equitable, scalable digital transformation of WASH services in low-income and humanitarian settings.