Validation of Francis–Kaplan Turbine Blade Strike Models for Adult and Juvenile Atlantic Salmon (Salmo Salar, L.) and Anadromous Brown Trout (Salmo Trutta, L.) Passing High Head Turbines

Samuel Shry,Gustav Hellström,Olle Calles,Linda Vikström,Kjell Leonardsson,Johan Leander

doi:10.3390/su12166384

Samuel Shry, Gustav Hellström + Show 4 more

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https://doi.org/10.3390/su12166384

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Abstract

The negative effects of hydroelectric power (HEP) on salmonid populations has long been recognized and studied. Downstream passage through turbines may potentially constitute a significant source of mortality for both juvenile and adult fish in regulated rivers. Numerical models have been developed to calculate turbine passage mortality based on the probability of collision with the turbine blades, but although widely used in management and conservation, their performance is rarely validated in terms of the accuracy and bias of the mortality estimates. In this study, we evaluated commonly used blade strike models for Kaplan and Francis turbines by comparing model predictions with observed passage mortalities for juvenile 13–27 cm and adult 52–94 cm Atlantic salmon (Salmo salar, L.) and anadromous brown trout (Salmo trutta, L.) acquired by acoustic telemetry. Predictions made for juveniles aligned closer with observed mortality for both Kaplan and Francis turbines (within 1–3% percentage points). However, the model severely underestimated the mortality of adult fish passing through Francis turbines, with up to 50% percentage points difference between predicted and observed mortalities. Furthermore, the model did not capture a clear negative correlation between mortality and discharge observed for salmon between 50–60 cm (grilse). We concluded that blade strike models are a useful tool for quantifying passage mortality for salmonid smolts passing large, high-head turbines, but that the same models should be used with care when trying to estimate the passage mortality of kelts in iteroparous populations. We also concluded that the major cause of passage mortality for juveniles is injury by collision with the turbine blade, but that other factors seem to contribute substantially to the passage mortality of kelts. Our study reports low mortality for smolts up to 27 cm passing through Kaplan and Francis turbines (0–12%), but high mortality for salmon over 50 cm passing though Francis turbines (56–81%).

Highlights

Hydroelectric power (HEP) complexes often lack functional solutions for downstream migration, forcing downstream migrating fish to pass through turbines or spill
We have shown that a commonly used deterministic blade strike model is a useful management tool for estimating turbine mortality for juvenile salmon and trout passing both Kaplan and Francis turbines, even for complex station designs with high heads, such as the Stornorrfors station
We have shown that the same model performs poorly when predicting the mortality of adult fish passing through Francis turbines, and, conclude that other tools, such as computational fluid dynamics (CFD) modelling or an autonomous sensor device (Sensor Fish) [35,43], are likely more suitable when making inferences on turbine loss for large salmonids

Summary

Introduction

Hydroelectric power (HEP) complexes often lack functional solutions for downstream migration, forcing downstream migrating fish to pass through turbines or spill. Empirical studies on live fish have traditionally been used to study mortality from passage through turbines and other routes at hydropower stations (some examples are [4,5,6]). These methods can provide accurate and reliable estimates of mortality, they require that tagged fish are either re-captured or monitored after passage to determine their fate, resulting in logistically challenging and often expensive field studies that are bound by the operating configuration of the hydropower station [7]. Most numerical models provide quantitative estimates of mortality by modeling the risk of mortality as a function of turbine and fish characteristics [8,9]

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