三峡大坝下游溶解氧变化特性及影响因素分析

根据三峡工程坝区水域实测数据,分析了水库蓄水以后大坝上、下游断面溶解氧浓度和溶解氧饱和度的变化特性,探讨了水位、流量因素对大坝下游水体溶解氧量的影响。结果表明,坝身孔口过流水体大量掺气后进入下游河道导致下游水体溶解氧浓度和饱和度显著增加,甚至达到超饱和状态。由于电站过流基本不改变水体溶解氧量,在电站和坝身孔口同时过流时,两种水体掺混后,下游溶解氧量主要受流量比的影响。此外,下游溶解氧量随流量的增加和下游水位的升高而增大。过坝总流量超过35 000 m3/s,下游水位超过68 m以及坝身孔口过流流量占总流量的绝大部分时,需特别重视溶解氧超饱和现象对水生生物可能造成的影响。

Analysis of the variety and impact factors of dissolved oxygen downstream of Three Gorges Dam after the impoundment

The variety and impact factors of the dissolved oxygen (DO) concentration and saturation at the two sections, upstream or downstream, of the Three Gorges Project dam after the impoundment are analyzed based on the field data. The results reveal that, since a great deal of oxygen dissolves into water due to the air entrainment when water sluices through the orifices, the phenomenon of DO super-saturation is observed in the downstream of the dam. However, DO concentration (saturation) in the downstream hardly varies if water sluices through the electricity power stations. When water sluices through the electricity power stations and orifices synchronously, DO concentration (saturation) of the downstream is mainly affected by the ratio of the two discharges. Additionally, the downstream water level also has an impact on the downstream DO concentration. When the total discharge is more than 35000m3/s and the downstream water level is higher than 68m, or when most of the discharge sluices through the orifices, great attention must be paid to the effect of DO super-saturation on the aquatic.