STR 2.02.03:2003 – Fish Passes: Main Provisions Technical Regulation
The Technical Building Regulation STR 2.02.03:2003, titled Žuvų pralaidos. Pagrindinės nuostatos (Fish Passes: Main Provisions), was issued by the Ministry of Environment of the Republic of Lithuania under Order No. 565. This regulation, which entered into force on January 1, 2004, establishes the mandatory technical requirements for the design, construction, and operation of fish passes across Lithuanian water bodies. It functions within the legal framework of the Law on Construction and the Law on Water, ensuring that engineering barriers do not impede the movement of migratory species.
The document's scope covers the classification of passage structures, their hydraulic calculation methods, and the biological parameters necessary for effective fish transit. It specifically addresses the needs of active migratory species such as Atlantic Salmon (lašiša), Sea Trout (šlakis), Vimba (žiobris), and European Eel (ungurys). The regulation defines specific structural types including fishways, bypass channels, fish locks, and mechanical lifts, providing detailed technical annexes and schemes for various hydraulic conditions.
This technical framework is binding for all construction participants, public administration entities, and owners of engineering communications or transport infrastructure. It ensures that any hydraulic structure classified under Class IV of hydrotechnical buildings meets the essential safety and functional requirements for ecological connectivity.
Classification of Fish Passage Structures
Chapter V of the regulation classifies fish passes based on their operating principles, relationship to the environment, and composition. The document distinguishes between several primary types of passage engineering:
- Fishways (žuvitakiai): Sloping artificial channels where water velocity is reduced to allow fish to swim upstream. Variants include stone fishways, flume-type passes with baffles, and pipe fishways.
- Bypasses (žuvų apylankos): Channels built around a migration barrier to simulate natural stream conditions.
- Fish Locks (žuvų šliuzai): Cyclical structures that transfer fish between water levels using a locking principle, typically used at higher dams.
- Fish Lifts (žuvų keltuvai): Mechanical or hydraulic lifting systems that move fish vertically in chambers.
- Fish Transports (žuvų perkėla): Systems involving the capture and transport of fish via specialized vehicles or containers.
Biological and Technical Characteristics of Migratory Fish
Designers must account for the swimming capabilities and behavior of specific fish species. Chapter IV defines critical biological data used for hydraulic modeling:
- Cruising speed (kruizinis greitis): The speed a fish can maintain for long durations in still water.
- Burst speed (spurtinis greitis): Maximum speed achievable for short periods (seconds or minutes) to overcome rapid currents.
- Attraction flow (viliojimo valktis): The specific zone of water velocity at the pass entrance designed to attract fish to the structure.
- Salmonid Requirements: Salmon and sea trout often require jump heights (liejimosi aukštis) between 10–15 cm in pool-and-weir fishways.
Hydraulic Calculations and Structural Design
Chapter VIII details the mandatory hydraulic formulas for calculating passage efficiency. Key design phases include determining the effective length and width of the attraction flow to ensure the fish can locate the entrance.
- Discharge Calculations: Formulas (8.3) and (8.5) are used to determine flow through notches and submerged orifices based on the discharge coefficient and head height.
- Energy Dissipation: For pool-type fishways, the energy dissipation (E) must not exceed 250–300 W/m³ for salmonids and 150–200 W/m³ for other species.
- Trash Racks: To prevent fish from entering turbines at the upper pool, gratings must have a maximum gap of 30–35 mm between bars.
Essential Requirements for Engineering Structures
As engineering structures, fish passes must comply with five essential requirements specified in Chapter IX:
- Mechanical resistance and stability: Structures must withstand water pressure and environmental loads without causing damage to nearby hydraulic works.
- Hygiene, health, and environment: Materials must not degrade water quality or damage local habitats.
- Safety in use: Design must prevent human accidents, such as falls or slips, especially around maintenance walkways.
- Noise protection: Equipment must not exceed environmental noise limits that could disturb migratory behavior.
- Energy economy: While ensuring sufficient flow for fish, the design should minimize water loss for hydroelectric power production.
Frequently Asked Questions
What is the maximum head height for a standard fishway design?
Fishways are generally constructed for migration barriers with a head height of up to 10 meters; for barriers exceeding this, specific technical and economic justifications are required.
What is the required gap for protective gratings in fish passes?
To prevent fish from being swept into turbines or other hazardous areas, the gap between the bars of the protective trash racks must be between 30 and 35 mm.
Which fish species are prioritized under STR 2.02.03:2003?
The regulation prioritizes salmonids, including Atlantic Salmon (lašiša) and Sea Trout (šlakis), as well as protected species like Vimba (žiobris) and European Eel (ungurys).
How is the attraction flow defined for fish pass entrances?
The attraction flow (viliojimo valktis) is a zone of submerged water jets designed with specific velocities to lure fish into the entrance of the passage structure from the search area below the barrier.
What are the allowed energy dissipation limits for fishway pools?
For salmonid species, energy dissipation should be between 250–300 W/m³, while for other species, the limit is lower, between 150–200 W/m³.
Is an ichthyological study required before designing a fish pass?
Yes, mandatory biotechnological data must include primary migratory species, their abundance, migration timing, and characteristic swimming speeds based on ichthyological research.
