This study presents strontium isotope and major ion data of shallow groundwater and river water from the Ile du Chambon catchment, located on the Allier river in the Massif Central (France). There are large variations in the major-element contents in the surface-and groundwater. Plotting of Na vs. Cl contents and Ca, Mg, NO 3 , K, SO 4 , HCO 3 , Sr concentrations reflect waterrock interaction (carbonate dissolution for Ca, Mg, HCO 3 and Sr because the bedrock contains marly limestones), agricultural input (farming and fertilising) and sewage effluents (for NO 3 , K, SO 4 ), although some water samples are unpolluted. Sr contents and isotope ratios ( 87 Sr/ 86 Sr vary from 0.70892 to 0.71180 along the hydrological cycle) in the groundwater agree with previous work on groundwater in alluvial aquifers in the Loire catchment. The data plot along three directions in a 87 Sr/ 86 Sr vs. 1/Sr diagram as a result of mixing, involving at least three geochemical signaturesAllier river water, and two distinct signatures that might be related to different water-rock interactions in the catchment. Mixing proportions are calculated and discussed. The alluvial aquifer of the Ile du Chambon catchment is considered, within the Sr isotope systematic, in a larger scheme that includes several alluvial aquifers of the Loire Allier catchment.