This document is concerned with the assessment of fish survival in pumping stations and hydropower plants, defined as the fraction of fish that passes an installation without significant injury. It does not concern indirect consequences of such installations, usually included in the notions ‘fish safety’ or ‘fish-friendliness’, like avoidance of fish affecting migration, behavioural changes, injury during attempted upstream passage, temporary stunning of fish resulting in potential predation, hypoxia due to depleted oxygen levels in turbine intakes positioned deep below the water surface, or the opposite, gas bubble disease in highly turbulent water near the discharge of a turbine.
This document applies to pumps and turbines as well as pumping stations and hydropower plants that operate in or between bodies of surface water, in rivers, in streams or estuaries containing resident and/or migratory fish stocks. Installations include centrifugal pumps (radial type, mixed-flow type, axial type), Archimedes screws, and water turbines (Francis type, Kaplan type, Bulb type, Straflo type, etc.).
The following methods to assess fish survival are described:
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Survival tests involving the paired release of live fish, introduced in batches of test and control fish upstream and downstream of an installation, and the subsequent recapture in full-flow collection nets. The method is applicable to survival tests in the field and in a laboratory environment. (Clause 6);
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A validated model-based computational method consisting of a blade encounter model and correlations that quantify the biological response to blade strike (Clause 7). The model is applicable to pumping stations and hydropower plants with a low to medium head (<8 m) in which blade strike forms the primary cause of fish damage in most cases.
The computational method can be used to scale results from laboratory fish survival tests to full-scale installations operating under different conditions (Clause 8).
The survival tests and computational method can also be applied to open-water turbines, with the caveats mentioned in Annex C.
The results of a survival test or a computed estimation can be compared with a presumed maximum sustainable mortality rate for a given fish population at the site of a pumping station or hydropower plant. However, this document does not define these maximum rates allowing to label a machine as “fish-friendly”, nor does it describe a method for determining such a maximum.
This document offers an integrated method to assess fish survival in pumping stations and hydropower plants by fish survival tests and model-based calculations. It allows (non-)government environmental agencies to evaluate the impact on resident and migratory fish stocks in a uniform manner. Thus the document may help to support the preservation of fish populations and reverse the trend of declining migratory fish stocks. Pump and turbine manufacturers will benefit from the document as it sets uniform and clear criteria for fish survival assessment. Further, the physical model that underlies the computational method in the document, may serve as a tool for new product development. To academia and research institutions, this document represents the baseline of shared understanding. It will serve as an incentive for further research in an effort to fill the omissions and to improve on existing assessment methods.
