水温是水生态系统中关键的环境因子，对水生生物的生存繁殖和水环境系统生态平衡具有重要作用。大型水库建成蓄水后改变原有河道水温结构，垂向上会出现水温分层现象。以澜沧江小湾水电站为研究对象，获取坝前1~200  m水深不间断高密度水温数据，开展小湾水电站坝前垂向水温分布特征研究。结果表明：小湾水库为典型分层型水库，坝前水温存在全年分层现象，夏季分层现象最明显，冬季分层现象最弱；表底层水温年平均温差达8.14 ℃，水温相对水深年变化率为0.05 ℃/m；坝前表层水温与气温呈正相关关系,水温最值出现时间较气温滞后；温跃层厚度变化趋势与深度相反，温跃层深度随季节发生变化，春季温跃层深度下降，冬季上升，夏秋两季处于稳定状态。

Water temperature is a key environmental factor in the aquatic ecosystem,and it plays an important role in the survival and reproduction of aquatic organisms as well as the ecological balance of the aquatic environmental system.The building of large reservoirs will change the original water temperature structure of the river,and the water temperature stratification will appear in the vertical direction.Due to the limitation of observation conditions and methods,the stratified observation of water temperature in reservoirs with water depth over 200 m is seldom carried out both in China and overseas.In this study,Xiaowan Hydropower Plant on Lancang River was taken as research object,and the uninterrupted high density water temperature data of 1-200 m depth in front of the dam was obtained to examine the vertical water temperature distribution characteristics in front of the dam of Xiaowan Hydropower Plant.The results showed that Xiaowan Reservoir was a typical stratified reservoir with annual water temperature stratification in front of the dam,which appeared most obvious in summer and most subtly in winter.The annual average temperature difference of surface and bottom water was 8.14 ℃ and the annual change rate of water temperature relative to water depth was 0.04 ℃/m.There was a positive correlation between surface water temperature and air temperature in front of the dam,and the maximum water temperature appeared lags behind the air temperature.The changing trend of thermocline thickness was opposite to the depth and the depth of thermocline decreased in spring,increased in winter while remained stable in summer and autumn,respectively.

云南省自然科学研究重点项目（2017FA021）；“十三五”国家重点研发计划（2016YFA0601601）