For studying cumulative effects to water temperature of diversion cascade plant, the water temperature distribution of every cascade plant were predicted using the vertical one-dimensional water temperature model and warming rate in this paper. By analyzing the forecasting result, three forms of cumulative effects to water temperature were gained, namely (1)Operation of first reservoir changed downriver water temperature distribution, induces water temperature delay phenomena: In the spring warming postponed, In the autumn cooling delayed. The water temperature delay phenomenon was transferred by diversion, so the water temperature delay phenomena of downriver cascade plant was more obvious. (2) Water temperature of plant tended to flat. Flat phenomenon of water temperature in the plant became more obvious from first cascade to last cascade. (3)Longitudinal water temperature change was reduced. The results provided scientific foundation for environmental impact assessment of river basin development.
