Xiluodu power station will discharge cold water to downstream in spring after operation and influence the fish breeding at downstream. Modification of the reservoir operation curve is studied to reduce this impact. Three kinds of operation curves are supposed. 2-D laterally averaged k–ε temperature model is adopted to study the water temperature structure in reservoir and the outflow temperature. The result shows during the temperature lifting time from January to June, the increase of the flow discharge will accelerate the decrease of the water level, which will raise the water temperature on the surface and cause the thermocline moving down to the bed. Then more warm water will be led from the surface to the outlet, and the downstream water temperature will rise. The reservoir operation could reduce and avoid the impact of cold water on fish breeding to some degree.
