River damming alters natural attributes of rivers, with consequences on water cycle in the river catchment. In this study, water samples including stratified water from four cascadereservoirs in the Jialing River basin were collected in January, April, July, and October in 2016. The hydrogen and oxygen isotopic compositions and their spatial and temporal variations wereanalyzed to assess the impacts of dam interception on water cycle in the river basin. The results showed that the δ¹⁸O and δD values of the surface water were generally turning positive along with the flow path due to the latitude effect and the dam interception. The δ¹⁸O values of the water samples were more positive in January and October than those in April and July, which should be resulted from the variations in the amount and sources of precipitation. In the summer stratification period, the range of¹⁸O value in the reservoir with thermal stratification (Tingzikou reservoir) was larger than that in other seasons. In contrast, it was not the case in other reservoirs. Moreover, reservoir stratification led to divergence in hydrogen and oxygen isotopic compositions between the discharged water and the surface water near dam. The existence of cascade reservoirs enhanced watershed evaporation, which might be responsible for the greater deviation of thehydrogen and oxygen isotope compositions of the river water from the local meteoric water line. The evaporation in the summer (July) was the strongest in the study area, followed by the spring (April) and the weakest in the winter and autumn (January and October).