Who is being left behind in water security, where do they live, and why are they left behind towards the achievement of the 2030 agenda?

The study focuses on sustainable development goal (SDG) 6, target 6.1.1 examining the proportion of the population using safely managed drinking water (SM). The SDGs aim to leave no one behind (LNOB) in development by 2030, this paper investigates if anyone is being left behind in accessing SM. We use world regions, countries globally, and 23 countries identified globally as critically water insecure (CWIC). The results indicate none of the CWIC had over 50% of the population accessing SM, but had over 50% using improved water, and over 10% using surface water. Sub-Saharan Africa had the lowest percentages using SM, and the highest using surface water in 2020. Pre-primary schools lag behind primary and secondary schools in accessing basic water services. Tanzania, Burundi, Papua New Guinea, and the Solomon Islands have below 50% of pre-primary schools with basic water. Households and schools using unimproved water sources are mostly from low-income and low climate resilience countries, fragile countries, and rural areas of CWICs characterized by high levels of poverty, food insecurity and illiterate women; subsequently exacerbating stunting and child mortality rates. These negative outcomes are largely consequences of poor institutional quality common to CWICs. Previous studies failed to highlight good governance, rigorously examine CWICs, and NOLB in water -health-food insecurity nexus. The stakeholders of the 2030 Agenda on water security can use these findings to accelerate the progress of leaving no one behind.