三峡水库蓄水不同阶段总磷的变化特征

基于三峡水库2003年后的蓄水特点，本文将2003~2017年划分为4个蓄水阶段.根据三峡水库2003~2017年每月的水文水质数据，分析了自蓄水以来不同蓄水阶段总磷的变化特征.研究发现，首次蓄水阶段，三峡水库的滞留效应从2005年开始凸显.蓄水试运行阶段，干流断面总磷年均浓度在2008年沿程明显降低，此后清溪场断面受到乌江高浓度总磷汇入的一定影响.高水位正常运用期，除清溪场断面外，从铜罐驿至官渡口断面，总磷年均浓度呈现沿程降低的现象.上游梯级电站运行后，除官渡口断面外，干流其余断面总磷年均浓度随时间逐渐减小.官渡口断面于2016年首次出现总磷年均浓度高于沱口断面的现象.且总磷丰水期年均值不再明显高于枯水期.同时，在此蓄水阶段总磷浓度与流量相关性不显著，朱沱，铜罐驿和官渡口断面总磷浓度与悬浮物浓度相关性不显著.

Variation characteristics of total phosphorus in different periods in the Three Gorges Reservoir after its impoundment

Based on the monthly water quality and hydrology data from 2003 to 2017, the variation characteristics of total phosphorus (TP) was investigated in the four periods which were divided by the different impoundment feature of the Three Gorges Reservoir after 2003. In the initial water impoundment process, the phosphorus retention effect of the Three Gorges Dam began at 2005. During the trial impoundment period, a marked decrease was observed in annual mean TP concentration along the main stream of the reservoir in 2008. Since then, the TP concentration in Qingxichang section was affected due to the inflow of Wu River with the high TP concentration. At the water level of 175m, there was a dramatic decrease in annual mean TP concentration from Tongguanyi sections to Guandukou section except Qingxichang section. After the operation of cascade hydropower stations upstream, a marked reduction of annual mean TP concentration happened along the main river channel sections except Guandukou section. A higher annual mean concentration of TP in Guandukou section than that in Tuokou section was observed for the first time in 2016. Meanwhile, the average concentration of TP in the flood season was no longer significantly higher than that in the dry season. In this period, no significant correlation was found between the concentration of TP and the water flow discharge in almost sections. In addition, no significant correlation was found between the concentration of TP and suspended volatile matters (SS) in Zhutuo, Tongguanyi and Guandukou section.