Modelling |
Emergent thinking in fish passage
Kleinschmidt Associates’ Emergent™ modelling framework is helping engineers better understand how fish move through complex hydraulic environments, offering new insights for designing effective fish passage systems at hydropower and river infrastructure projects.
These three figures depict viable migratory routes at 1000, 5000, and 14500 cfs respectively. Note the majority of viable passage routes occur at medium discharges, while fish are forced to side channels at high discharges
HYDROPOWER OPERATORS WORLDWIDE face an increasingly complex challenge: maintaining reliable renewable energy generation while protecting migratory fish populations that depend on healthy river connectivity. Fish passage systems such as ladders, bypass channels and attraction flows are now a standard feature of many dams, yet designing structures that perform well biologically – rather than simply meeting hydraulic criteria – remains a persistent engineering challenge. Fish behaviour is highly variable and influenced by environmental conditions, schooling dynamics and energy expenditure, meaning that predicting how fish will respond to a particular hydraulic design is far from straightforward. A new modelling framework developed by Kleinschmidt Associates is offering engineers and river managers a different way to approach that challenge. The company received a 2025 Business Achievement Award from Environmental Business Journal (EBJ) in the Information Technology category for its Emergent™ framework, a modelling platform designed to simulate how fish navigate real-world river systems and hydropower facilities. Developed by Senior Scientist Kevin Nebiolo, the system combines hydrodynamic modelling with biological and behavioural simulation to provide insight into how fish actually move through complex flow environments. By integrating fish energetics, schooling behaviour and hydraulic conditions within a single framework, the model helps engineers and regulators to evaluate fish passage designs and operational strategies prior to construction or operation. At the heart of the approach is a shift in how fish
are represented in simulation. Traditional modelling methods often treat fish as passive objects moving through hydraulic fields, focusing primarily on whether water velocities exceed the swimming capabilities of
a particular species. Emergent instead treats fish as autonomous agents capable of making decisions in response to their environment and neighbours. “The key ideas here are autonomy and agency,” Nebiolo explains. “In Emergent the simulated fish have agency and they make decisions that maximise their own well-being.” This agent-based approach allows simulated fish
to behave more like real ones. They instinctively form schools, move together for protection and respond to local cues in their environment rather than possessing complete knowledge of the entire system. The digital fish react to nearby neighbours, follow one another, queue at constrictions and draft behind other fish to conserve energy. Despite having only local awareness of their surroundings, the simulated individuals can still produce coordinated collective movements that resemble natural migration patterns. These behaviours allow the model to reveal patterns such as congestion points, resting areas and alternative passage routes that traditional hydraulic analysis might overlook.
Integrating biology with hydraulics The Emergent framework integrates three different
scientific components that historically have often been analysed separately. The first is hydrodynamics, typically generated from established river models that describe flow velocities and depths throughout a river reach or dam approach area. These models provide the physical environment through which fish must move. The second component incorporates long-established biological equations describing swimming energetics and fatigue. These models estimate how long fish can sustain certain swimming speeds and how energy expenditure accumulates as they attempt to pass through areas of faster flow. Such equations are widely used in fisheries science and provide important limits on
26 | April 2026 |
www.waterpowermagazine.com
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