长江向家坝建库对库区水体温热收支定量研究

Quantitative effect of Xiangjiaba Reservoir operation on thermal budget of river flow in reservoir area

向家坝等水库的修建和调度一方面为人类发展提供了宝贵的水资源和清洁能源,另一方面也改变了天然河道的温热收支过程。本研究利用水量平衡方程和能量平衡方程构建箱式模型,并辅以库区一维水动力模型来减小无坝条件下的库区河道的纵向水位分布计算误差,通过情景计算揭示了有无坝体各部分热量收支的占比及差。结果表明:水库的运行使得水体储热过程在时间尺度上更加稳定,建库后水体总热能为天然情况下的7~35倍,同时也使得库区水体具有一定的“滞温”效应,最高滞后42天;建库后库区水体接收的太阳辐射热能相较天然状态最高提升了388%,最低提升283%,蒸发耗能方面的热量损耗最高提升了391%,最低提升284%,两者热能提升的最高值和最低值均发生在2月和8月,总体效应为热能净收入增加。研究结果可为梯级水库的规划、建设和调度对温热收支的影响提供重要依据,在温热影响层面为保护库区上下游水体生态系统提供部分科学支持。

The construction and operation of reservoirs,such as the Xiangjiaba dam,provide invaluable water resources and clean energy for human development,but alter the thermal energy balance of the natural river channels.This study uses the water balance equation and energy balance equation to develop a box model,supplemented by a one-dimensional hydrodynamic model for the reservoir area,to reduce the errors in calculating the water profiles of the reservoir channels under dam-free conditions.Scenario calculations reveal the proportion and difference in each component of the heat budget with and without the presence of the dam.The findings indicate that compared with the natural river case,reservoir operation has enhanced the temporal stability of water thermal storage process;the total thermal energy of the water body is 7 to 35 times that of the natural state.The operation imparts a certain"thermal inertia"effect to the water body in the area,with the longest time lag reaching 42 days.Solar radiation received by the water body presents a maximum increase of 388%and a minimum increase of 283%compared to the natural state;for heat loss in evaporative energy,its maximum increase reaches 391%and minimum increase 284%.Of both thermal energy increments,the peak and trough occur in February and August,respectively.As a result,the overall effect has been an increase in net heat income.This study lays an important basis for thermal budget estimation during planning,construction,and regulation of cascade reservoirs,and helps protect the water ecosystems of large reservoirs.