Adequate access to drinking water for hydration and hygiene depends on many factors, such as water quality, accessibility, continuity of supply, and available quantity. We developed the Drinking Water Security Index (DWSI) to assess relative multifactorial drinking water security at different spatial and temporal scales. We apply this new index in Sudan to assess historical and future drinking water security at state, local, and maternity levels. State-level analyses found that the Red Sea and River Nile states are most vulnerable, with the lowest DWSI for both historical and future periods. The 1 km2 pixel level analysis shows large differences in water security within the major states. Analyses at maternity level showed that nearly 18.97 million people are affected by the 10% of maternities with lowest DWSI, a number projected to increase by 60% by 2030. Current and future water security indexes of maternities providing Emergency Obstetric and Newborn Care, were assessed to identify those where urgent action is needed to ensure quality health care in water secure conditions. This work provides useful information for stakeholders in the health and drinking water sectors in Sudan, to improve public health, reduce preventable mortality, and make the population more resilient to projected environmental changes.