The Turbidity and Gastroenteritis Study aims to establish and characterize the link between the turbidity level of distributed water and the number of cases of acute gastroenteritis requiring medical care (AGEC) observed in the service area. This component of the study covers 19 municipalities in the Greater Nancy Urban Community and more than 240,000 people. The Saint-Charles (now defunct) and Edouard Imbeaux plants are supplied with water from the Moselle River, pumped from the municipality of Messein. The raw water is treated through standard stages of clarification, sedimentation, filtration, and disinfection. The incidence of AGE was obtained from health insurance data for the period 2002 to 2007. The method involved regressing, using a generalized additive model, the incidence of GEAm against daily water turbidity levels, and then, in a second step, against several other plant operating parameters to identify risk factors for GEAm. The results do not show a convincing relationship between the turbidity levels of the treated water and the risk of GEAm. However, the risks appear to be more pronounced at high water temperatures. The effect of temperature must be taken into account to better understand the role of distributed water turbidity on the risk of GEAm. The results of this study confirm that low-flow periods are when the risk of GEAm is highest for water treatment plants using surface water sources.