Groundwater can serve as an alternative water supply source under severe drought conditions. There is a lack of research addressing the combined effects of extreme drought, groundwater access (GA), water security and health outcomes. This study adopted a descriptive ecological approach and time-series analysis to analyze the impact of severe drought and GA on water security and the prevalence of diarrhea-related hospitalizations. The study encompassed the populations of 10 munici-palities in a large semi-arid region that has been impacted by historical drought. Municipal data, including groundwater use licenses, diarrhea hospitalizations, and frequency of water truck services, were collected focusing on the period from January 2012 to March 2020. Drought events were quantified based on the standardized precipitation index. Pearson correlation and a backward-stepwise multiple linear regression were used to investigate the association between the studied variables. A higher number of groundwater-use licenses and less severe drought conditions were associated with a reduced reliance on water trucks (adjusted coefficient of determination, R-adj(2). = 0.74; p < 0.005), with GA having a slightly greater influence than drought severity. GA was also associated with fewer hospitalizations, while prolonged but less severe droughts were linked to increased hospitalizations ( R-adj(2). = 0.75; p < 0.01). Drought magnitude had a twofold greater impact than drought duration or GA. To enhance water security and reduce hospitalizations, there is a critical need to implement groundwater management alongside drought management strategies. These measures are particularly urgent given the intensification of droughts pro-jected under climate change scenarios.