The cascade development of water resource will lead to cumulative effect of supersaturated total dissolved gas (TDG) on the ecological environment, which will cause lethal disease to fish. The TDG dissipates slowly in deep reservoir areas and if supersaturated TDG can't recover through the spillway then it will lead to continuous accumulation in the stilling basin. In order to investigate the cumulative effect of supersaturated TDG of hydropower cascades, a validated TDG numerical model with the VOF method and DES model was used to simulate a spillway discharge of Tongjiezi dam with supersaturated TDG and 100% TDG inflow. In this model, bubble size change is calculated by bubble number density equation and TDG is simulated by transport equation considering the gas-liquid mass transfer. Comparing with the TDG 100% inflow case, it indicated forebay TDG level caused by the upstream dams should be considered and involved in the downstream TDG evaluation. This paper also proposed an engineering measure with baffle blocks in the spillway which can reduce entrained bubble mass and TDG saturation level at the entry point than the case without blocks. It shows baffle blocks in the spillway can effectively reduce the cumulative effect of supersaturated TDG. It is a critical step for the mitigation of accumulation of supersaturated TDG through the spillway and the results provide reference about mitigation measure of supersaturated TDG for hydropower cascades.

水资源的梯级开发将导致过饱和总溶解气体（TDG）对生态环境的累积影响，这将导致鱼类致死性疾病。TDG在深水库区域消散缓慢，如果过饱和TDG无法通过溢洪道恢复，那么它将导致在静水盆地中不断堆积。为了研究水电梯级过饱和TDG的累积效应，采用了VOF法和DES模型验证的TDG数值模型，对过饱和TDG和100％TDG入水的通街子大坝溢洪道流量进行了模拟。在该模型中，考虑到气液传质，通过气泡数密度方程计算气泡尺寸变化，并通过传输方程模拟TDG。与TDG 100％流入案例相比，它表明应考虑上游大坝引起的前湾TDG水平，并参与下游TDG评估。本文还提出了一种在溢洪道中设置挡板块的工程措施，与没有挡板的情况相比，该措施可降低入口点的夹带气泡质量和TDG饱和度。它表明溢洪道中的挡板块可以有效地降低过饱和TDG的累积效应。这是缓解溢洪道中过饱和TDG积累的关键步骤，研究结果可为水电梯级中过饱和TDG的缓解措施提供参考。本文还提出了一种在溢洪道中设置挡板块的工程措施，与没有挡板的情况相比，该措施可降低入口点的夹带气泡质量和TDG饱和度。它表明溢洪道中的挡板块可以有效地降低过饱和TDG的累积效应。这是缓解溢洪道中过饱和TDG积累的关键步骤，研究结果可为水电梯级中过饱和TDG的缓解措施提供参考。本文还提出了一种在溢洪道中设置挡板块的工程措施，与没有挡板的情况相比，该措施可降低入口点的夹带气泡质量和TDG饱和度。它表明溢洪道中的挡板块可以有效地降低过饱和TDG的累积效应。这是缓解溢洪道中过饱和TDG积累的关键步骤，研究结果可为水电梯级中过饱和TDG的缓解措施提供参考。