A seminar at World Water Week 2014 brought together learning from Brazil and Sweden to examine how hydropower’s effects on the flow regimes of rivers can be sustainably managed.

Held on Tuesday 2 September, The power of flows: negotiating sustainable hydropower through environmental flows explored tools, case studies, policy and science on the subject. You can watch the full seminar here.

A key presentation was made by Domingo Fernandez, fish specialist at Itaipu Binacional, and Paraná river basin academics on the example of Canal da Piracema – the world’s largest fish passage system – at the 14,000 Itaipu hydropower plant.

Completed in 2002, Canal da Piracema is a 10km-long artificial river which connects the Itaipu reservoir to the Paraná river downstream of the plant, allowing migratory fish to reach spawning and nursery grounds in tributaries upstream of the plant, and return during autumn and winter. Monitoring has shown that every year, at least 85 per cent of the total species on the Paraná river basin pass through the channel.

Fish migration is a very site-specific topic; migratory species have different migration patterns in different river basins. However, as hydropower development continues to grow around the world, managing fish-migration, particularly in sensitive areas, is becoming an important expectation on developers and operators.

The study of Canal da Piracema (you can download the presentation slides here) was a good opportunity to recall wider considerations on fish migration:

• Tributaries are fundamental to spawning and nursery. Lotic stretches provide a good environment for spawning, while lentic stretches near the mouth are an ideal nursery for fingerlings.
• Attractiveness, efficiency and permeability are different among fishways and species, and so fish passages may be selective. As a result, there might have to be a call to maximise efficiency of the schemes for particular species.

Next steps and new challenges were identified, including:

• Technical and systemic evaluation of ecoflows. Improving knowledge of the flow will help to minimise the impacts and achieve a better survival rate of fish species
• Genetic, telemetry and swimming capacity studies to build knowledge on the similarities and differences of specific species, and their natural connections
• Improved design of fish passages. The most important aspects to consider are the position of the entrance, the water speed and water depth of the transposition facilities
• International collaboration – for example between Brazil and Sweden, which have similar problems but use different systems

A video interview with Domingo Fernandez will be available soon. You can download the slides from his presentation on 'fishing for the environment in Brazil' here, and you can find further resources from the seminar here.

Downstream flows and aquatic species are key topics for discussion at the 2015 World Hydropower Congress – find out more here.