Advancing Sustainable Hydropower: Mitigating Total Dissolved Gas Supersaturation Induced by Spillway Operation
Total Dissolved Gas (TDG) supersaturation caused by spillway operations presents a critical environmental issue that impacts downstream fish populations and their habitats. Based on field results, TDG supersaturation widely exists at Swedish dams but receives limited attention. This pioneering project aims to improve our understanding of spillway TDG generation mechanisms and develop innovative solutions to mitigate the negative effects on fish habitats. By addressing the overlooked TDG issues, this project will help safeguard aquatic ecosystems while supporting the nation's renewable energy goals, thereby contributing to a sustainable and resilient energy future.
Specifically, this project seeks to:
• Understand the complex mechanisms of TDG generation and dissipation in and downstream of spillways.
• Assess the impact of TDG supersaturation on fish habitats, focusing on the spatial-temporal habitat quality and availability.
• Develop and evaluate innovative mitigation strategies to reduce TDG levels, incorporating spillway design and operational strategies.
Project name and acronym: Advancing Sustainable Hydropower: Mitigating Total Dissolved Gas Supersaturation Induced by Spillway Operation
Project leader: Shicheng Li, Concrete building
Participating researcher KTH: Luigia Brandimarte, Sustainable Development, Environmental Science and Engineering
Adress: Teknikringen 10B, 10044 Stockholm
Participating companies: Vattenfall
Project period: 2025-07-01 - 2026-06-30
Funding: J. Gust. Richert stiftelse
The overarching aim of this project is to address a critical yet underexplored environmental issue stemming from 2025-148. J. Gust. Richert stiftelse Sweden’s extensive reliance on hydropower: the generation of supersaturated Total Dissolved Gas (TDG) in spillways and its detrimental effects on downstream fish and their habitats. Given that hydropower accounts for approximately 45% of Sweden’s national electricity generation, the sustainable management of its environmental impacts is not only essential for the preservation of biodiversity but also for aligning with Sweden’s energy and environmental policies, including the national relicensing plan for hydropower plants (Nationell plan för modern
miljövillkor, NAP), the EU Water Framework, and the Biodiversity Strategy for 2030.
This project seeks to fill a significant gap in our understanding and management of TDG-related impacts by:
(a) Investigating the mechanisms of TDG Generation
This will improve our understanding of the complex processes through which TDG is generated in spillways, including
the role of turbulence, aeration, and environmental factors, such as water temperature, which contribute to gas supersaturation.
(b) Quantifying impacts on physical habitats
This will assess how different levels of TDG affect the quality and quantity of habitats, providing insights into the
ecological health of aquatic ecosystems and the viability of fish populations.
(c) Developing mitigation strategies
This part will propose and test innovative solutions to reduce TDG supersaturation, including modifications to spillway
design, operational adjustments, and the exploration of new technologies.
The project represents a crucial step toward reconciling Sweden’s energy needs with its environmental responsibilities. By advancing our understanding of TDG dynamics and developing effective mitigation strategies, we can safeguard aquatic ecosystems while supporting the nation’s renewable energy goals, thereby contributing to a sustainable and resilient energy future.
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