水电能源科学

为揭示三峡水库水温相对气温的变化规律，采用正弦曲线拟合与滞回曲线分析两种方法，利用从朱沱到庙河8个断面的水温和附近气温数据，分析了三峡水库表层水温相对气温的滞后效应及其沿程变化特征。研究发现，三峡水库水温在3～8月的蓄能期低于气温，而在9月至次年2月的放能期高于气温，水温的年内变化滞后于气温；正弦曲线拟合的水温峰值出现时间晚于气温15～37 d,峰值滞后时间和滞回曲线面积均受水深影响而沿程增加；平均水深大于20 m的后6个断面滞后时间沿程增加趋势更为显著，而蓄能期平均水温受水深影响沿程降低，水气温差的绝对值沿程显著增大。结果表明，三峡水库表层水温相对气温的滞后效应受水深影响而沿程增强，在利用气温分析和估算水温变化时需要考虑水深变化的影响。

This study utilized sinusoidal curves and hysteresis loops to explore the relationship between surface water temperature and air temperature in the Three Gorges Reservoir, with a focus on the hysteresis effect of water temperature relative to air temperature along the main stream. Water temperature at a depth of 0.5 m below the surface was measured at eight cross-sections from Zhutuo to Miaohe, and corresponding air temperature data were collected. During the storage period(March to August), the water temperature was lower than the air temperature, but higher during the heat release period(September to February in the next year), indicating that intra-annual water temperature variations lag behind the air temperature. The lag time, calculated using a regressed sinusoidal curve(ranging from 15 to 37 days), along with the area of the hysteresis loops, increased downstream, primarily due to the increasing water depth at the cross-sections. This trend was particularly pronounced at the six cross-sections where the water depth exceeded 20 m. Additionally, the mean water temperature during the storage period decreased along the mainstream, resulting in an increasing difference between water and air temperatures. These findings suggest that the hysteresis effect of surface water temperature relative to air temperature strengthens downstream due to increasing water depth. Therefore, the impact of varying water depth should be considered when investigating or estimating water temperatures in the Three Gorges Reservoir based on air temperature.