Water quality and hydrologic connectivity in rural communities around the Manombo Special Reserve of southeastern Madagascar during the dry season

• We conducted a cross-sectional assessment of water quality during the dry season in and around the Manombo Special Reserve of southeastern Madagascar. • The majority of villages contained levels of total coliforms and Escherichia coli exceeding the World Health Organization standards and the Malagasy Potability Standards for drinking water. • E. coli levels similar to those recorded in this study have been associated with a high risk of the presence of fecal-borne pathogens. • There was a significant difference in E. coli levels between drinking-only and general-use sources. • Most water sources were prone to seasonal flow; some were vulnerable to upstream contamination; and the highest-order stream contained the highest E. coli levels. This study establishes a cross-sectional understanding of the water quality and hydrologic connectivity during the dry season among rural communities near the Manombo Special Reserve along the coast of the Atsimo-Atsinanana region of southeastern Madagascar, a region impacted by diarrheal disease, tropical cyclones, and flooding. Conducting one measurement per site during the dry season, we collected surface and well water samples from eleven rural villages outside the Manombo Special Reserve and surface water samples from nine locations within the Manombo Special Reserve and tested for inorganic and bacteriological contamination. Earth observation data was utilized to map the watershed, stream order, and connectivity between water sample sources in the study area. We found negligible inorganic contamination in all of the villages and areas of the Manombo Special Reserve. However, the majority of villages contained levels of total coliforms and Escherichia coli ( E. coli ) exceeding the World Health Organization standards and the Malagasy Potability Standards for drinking water. Village water sources were categorized into two types of use, drinking-only and general-use (e.g., for washing and bathing). There was a significant difference in E. coli concentrations between drinking-only and general-use sources. We did not find a substantial difference between E. coli levels in the Manombo Special Reserve and the villages. The watershed delineation revealed that the majority of the water sources were first-order ephemeral streams, and some of the drinking-only sources were located downstream from contaminated general-use sources. Investigation into E. coli strains and sources, seasonal variability and temporal trends, hydrologic dynamics, and climate-related events is required to understand the drivers of bacteriological contamination and associated health outcomes.