Abstract The natural hydrological regime of the Yangtze River has been influenced by dam construction over past decades. More reservoirs are being built and have been planned in the upper reach of the Yangtze River (URYR). To investigate the effects of reservoirs in the URYR and the Three Gorges Reservoir (TGR) on the water temperature regime, a reservoir water heat model combined with the Soil and Water Assessment Tool is used to simulate the water temperature change under different scenarios. The results show that the water temperature regime has been dramatically altered by reservoir operation, especially in spring and autumn. Reservoir operations impose a noticeable hysteresis effect on water temperature rising and falling processes, thereby resulting in a delay of the suitable temperature date for the Chinese Sturgeon (Acipenser sinensis) and four famous major carps. When more reservoirs are put into use, the delays in the target spawning times of these fishes will be further exacerbated. Modifying operation modes of these reservoirs and depth of water release is necessary during fish spawning seasons, which could facilitate a better balance between ecological and socioeconomic demands. We hope the results of this study will be useful to the river ecosystem health and stability.

中文翻译：

---

梯级水库对长江水温的影响：评价及生态意义

摘要 几十年来，长江自然水文情势受到大坝建设的影响。更多的水库正在建设和规划在长江上游（URYR）。为了研究URYR和三峡水库（TGR）中的水库对水温状况的影响，结合水土评估工具的水库水热模型用于模拟不同情景下的水温变化。结果表明，水库运行已显着改变了水温状况，尤其是在春季和秋季。水库运行对水温上升和下降过程有明显的滞后效应，从而导致中华鲟（Acipenser sinensis）和四大著名鲤鱼的适宜温度日期推迟。随着更多水库投入使用，这些鱼类的目标产卵时间延迟将进一步加剧。在鱼类产卵季节改变这些水库的运行模式和放水深度是必要的，这可以促进生态和社会经济需求之间的更好平衡。我们希望这项研究的结果对河流生态系统的健康和稳定有所帮助。这可以促进生态和社会经济需求之间的更好平衡。我们希望这项研究的结果对河流生态系统的健康和稳定有所帮助。这可以促进生态和社会经济需求之间的更好平衡。我们希望这项研究的结果对河流生态系统的健康和稳定有所帮助。