大渡河过饱和溶解气体原型观测研究

Prototype Observation and Study of Dissolved Gas Supersaturation in Dadu River

高坝泄洪会导致水中的总溶解气体(total dissolved gas,TDG)过饱和,其不利影响会持续较长范围,可能导致下游鱼类患气泡病甚至死亡。随着大量高坝的建成运行,这一生态环境问题更受关注。基于对大渡河水电站A的3年过饱和TDG原型观测数据,分析过饱和TDG生成释放的影响因素及其作用规律,并开展泄水方式优化的分析讨论。结果表明:不同的泄洪建筑物泄洪生成的过饱和TDG差异较为显著,深孔泄洪生成的TDG饱和度水平高于泄洪洞泄洪生成水平;TDG饱和度生成值与泄洪流量成较好的正相关关系,而与下游水位的关系并不显著;初始饱和度影响单位距离TDG饱和度降低值;水深是影响过饱和TDG释放的重要因素,水深越小的河段释放系数越大。基于3年原型观测数据的分析结果,进一步提出水电站A过饱和TDG生成预测模型,并对汛期的大坝泄洪调度提出减缓过饱和TDG影响的优化建议:当流量小于泄洪洞泄洪能力(1384 m^3/s)时,采用泄洪洞泄洪;当流量大于泄洪洞泄洪能力且小于2600 m^3/s时,采用单深孔与泄洪洞联合泄洪,可将生成的TDG饱和度控制在129%以下。多年期的原型观测研究丰富了高坝泄洪过饱和TDG的原型观测成果,为进一步探究过饱和TDG机制和减缓措施提供重要基础数据和技术支撑,对水电开发河流的水生态保护具有一定意义。

The discharge from high dams will lead to the supersaturation of total dissolved gas(TDG)in water.Its adverse effects will last for a long distance,which will cause the downstream fish get gas bubble disease and even die.With the construction and operation of a large number of high dams,this ecological environmental problem has attracted more attentions.Based on the three-year prototype observation sets of supersaturated TDG at dam A in Dadu river,it was analyzed about the influencing factors and rules of the generation and dissipation of supersaturated TDG,and an optimal discharge pattern for dam A was discussed.It is shown that the levels of supersaturated TDG generated by the discharge of different spillway buildings are significantly different.The saturation level generated by deep hole is higher than that generated by spillway tunnel.There is a good positive correlation between the generated value of saturation and the discharge.But the correlation between the generated TDG and the downstream water elevation is not significant.The level of initial saturation affects the decrease of TDG saturation per unit distance.Water depth is an important factor affecting the dissipation of supersaturated TDG.The shallower the water depth is,the greater the dissipation coef-ficient is.Based on the analysis results of three-year prototype observation data,a predictive model of TDG generation downstream of dam A was proposed.Optimal operation to mitigate the negative impact of TDG was discussed.A suggestion is that,when the flow is less than the discharge capacity of the spillway tunnel(1384 m^3/s),the spillway tunnel is recommended to discharge the flood,and when the flow is greater than the discharge capacity of the spillway tunnel and less than 2600 m^3/s,the combined discharge of a single deep hole and the spillway tunnel is suggested.In this way,the generated TDG saturation can be controlled below 129%.The multi-year prototype observation study enriches the prototype observation results of the supersaturated TDG of high dam discharge,which provide important field data and technical support for the further exploration of the mechanism of supersaturated TDG and mitigation measures.It is of significance for the water ecological protection of hydropower developed rivers.