Drinking water is a major concern for households in the Ouellé sub-prefecture. Its availability is a real problem for the population. This study aims to show the link between water supply methods and diarrhoeal diseases in the Ouellé sub-prefecture. The methodological approach involved analysing epidemiological data from the various dispensaries and CSUs in Ouellé from 2016 to 2020 and field surveys of 378 households. The results show that the lack of a permanent stream in the area makes it difficult for SODECI to supply drinking water to the population, particularly during the dry season. This dry period sees the highest rate of diarrhoea. From 2016 to 2020, the Ouellé sub-prefecture recorded 1,033 cases of diarrhoeal disease. During the dry season, 54.6% of cases of diarrhoea were diagnosed in this sub-prefecture. Households near water points suffer less from water-borne diseases than those further away. The construction of a new water tower would facilitate access to water for the entire population. Improving drinking water and sanitation in the villages could reduce the risk of diarrhoeal diseases.