SIST EN 18110:2025

SLOVENSKI STANDARD
01-november-2025
Kakovost vode - Ocena škode pri prehodu rib skozi črpalne postaje in
hidroelektrarne - Metode, ki temeljijo na preskusu preživetja rib in modelu udarca z
lopatico
Water quality - Assessment of damage to fish passing through pumping stations and
hydropower plants - Methods based on live fish passage survival test and blade strike
model
Wasserbeschaffenheit - Verfahren zur Ermittlung der Fischdurchgängigkeit von
Wasserförderschnecken, Pumpen und Spiralturbinen, die in Pumpwerken und
Wasserkraftwerken verwendet werden
Ta slovenski standard je istoveten z: EN 18110:2025
ICS:
13.060.01 Kakovost vode na splošno Water quality in general
93.160 Vodogradnja Hydraulic construction
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN 18110
EUROPEAN STANDARD
NORME EUROPÉENNE
September 2025
EUROPÄISCHE NORM
ICS 93.160
English Version
Water quality - Assessment of damage to fish passing
through pumping stations and hydropower plants -
Methods based on live fish passage survival test and blade
strike model
Wasserbeschaffenheit - Verfahren zur Ermittlung der
Fischdurchgängigkeit von Wasserförderschnecken,
Pumpen und Spiralturbinen, die in Pumpwerken und
Wasserkraftwerken verwendet werden
This European Standard was approved by CEN on 13 July 2025.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by
translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2025 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 18110:2025 E
worldwide for CEN national Members.

Contents Page
European foreword . 4
Introduction . 5
1 Scope . 9
2 Normative references . 9
3 Terms and definitions .10
4 Drawings of the installations .14
5 Equipment and tools .20
5.1 Collection net .20
5.2 Fish introduction device .21
5.3 Transport tank .23
5.4 Storage tank .23
5.5 Keepnet .23
5.6 Small transport tank .23
5.7 Measuring board .23
5.8 Anaesthetics .23
5.9 Fish welfare journal .24
6 Fish survival test .24
6.1 General .24
6.2 Authorization and safety .24
6.3 Legislation and directives .24
6.4 Flow charts .25
6.5 Operating conditions .30
6.6 Choice and origin of fish .30
6.7 Preparation of a fish survival test .32
6.8 Execution of a fish survival test .34
6.9 Calculation of passage survival .37
6.10 Report .38
7 Computational method to assess fish survival .41
7.1 General .41
7.2 Blade strike mortality .41
7.3 Probability of collision .42
7.4 Velocity in the meridional plane .43
7.5 Relative velocity of the fish .44
7.6 Effective fish length .44
7.7 Mutilation ratio .45
7.8 Strike velocity .46
7.9 Blade thickness .47
7.10 Total mortality .47
7.11 Integral mortality .48
8 Scaling of results of fish survival tests .48
8.1 General .48
8.2 Geometric similarity .48
8.3 Kinematic equality .49
8.4 Scaling in case of true similarity . 49
8.5 Scaling under practical conditions . 50
Annex A (informative) Fish species . 52
Annex B (informative) Causes of damage and mortality to fish passing through pumping
stations and hydropower plants . 53
Annex C (informative) Fish survival assessment for open-water turbines . 59
Annex D (informative) Survival estimates, statistical precision, power, and sample size . 67
Annex E (normative) Parameters to be described in a fish welfare journal . 76
Annex F (informative) Legislation on the protection of test animals used for scientific
purposes . 78
Bibliography . 79

European foreword
This document (EN 18110:2025) has been prepared by Technical Committee CEN/TC 230 “Water
analysis”, the secretariat of which is held by DIN.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by March 2026, and conflicting national standards shall be
withdrawn at the latest by March 2026.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights
Any feedback and questions on this document should be directed to the users’ national standards body.
A complete listing of these bodies can be found on the CEN website.
According to the CEN-CENELEC Internal Regulations, the national standards organisations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia,
Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland,
Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of North
Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and the United
Kingdom.
Introduction
Purpose of the standard
In recent years, there has been a growing focus on enhancing ecological water quality, with a specific
emphasis on fish populations. International legal frameworks, such as the Water Framework Directive
(WFD) [1], the European Eel Regulation [2], and the Benelux Free Fish Migration Decision [3], have played
a pivotal role in shaping the measures adopted in this regard. Human activities related to water
management, drinking water supply, irrigation, and electricity production require the installation of
pumps and turbines that can have significant environmental impacts on fish populations. For the
environmental sustainability of these sectors, their impact must be studied and, if needed, the best
available mitigation measures must be applied. It is the reason why significant efforts are being made by
various stakeholders, including water management authorities, resource agencies, pump and turbine
manufacturers, ecological consultancy firms, and research institutions, to enhance the chances of survival
for fish passing through pumping stations and hydropower plants.
To address these environmental challenges and ensure the effective protection of fish populations, it is
crucial to establish standardized procedures for assessing the impact of new and existing turbomachines
on fish survival. This standard aims at providing a basis for planning, conducting, and reporting fish
survival studies in pumps and turbines. It will lead to more consistency in results among study sites and
machines.
Mechanisms of fish mortality
Damage to fish in pumping stations or hydropower plants can have different causes [13]. Mechanical
injury by blade strike is generally regarded as the primary cause of injury and mortality in pumps and
turbines with low to moderate heads. Grinding of fish along rough walls or entrapment in small gaps and
clearances can also lead to damage. Other causes are rapid pressure changes that can result in
barotrauma, and excessive shear forces in a fluid flow with high velocity gradients. The actual pump or
turbine system is often where the risk is highest, but also other parts of a plant can be the source of
damage, for instance at trash racks, in nearly closed guide vanes, long pipelines, or siphons, near butterfly
valves, or oscillating no-return valves.
Methods to assess fish survival
Water management authorities are increasingly transitioning to the use of pump and turbine systems
that pose fewer risks to fish. Decisions to that effect are usually based on survival tests done in the field
at existing plants, or on laboratory experiments done in test facilities for new designs of pumps and
turbines that are safer for fish. These survival tests can use either live fish or artificial, dummy fish with
integrated sensors. Another alternative route to estimating fish survival is to use computational models
that are well-validated with information from prior tests. Each of these methods has its advantages and
disadvantages. The final choice depends on the stage of development and the desired level of accuracy.
1. Fish survival tests in the field
Fish survival tests conducted in the field at the actual plant site, using live fish and real environmental
and operational conditions, yield results that most closely reflect what will be experienced in practice.
The fish should be representative of the population for which the survival is being estimated, and
operating conditions should reflect the most common modes of operation, or worst-case conditions if
such conditions occur on a regular basis. Survival tests like these come closest to reality, where resident
fish are entrained naturally into the intake structure of a plant, are subjected to all stressors during
passage, and can display their natural behaviour. The use of artificial dummy fish with integrated sensors
[17], can give additional information but they cannot replace tests with live fish. While the recorded
values of acceleration, rotation, and pressure changes may give valuable information about stressors
along a trajectory, these readings alone are (as of yet) difficult to correlate with actual damage to fish.
Current studies are expected to improve their predictive powers.
Some previous studies of fish survival in existing plants use naturally-entrained fish that are collected in
nets after passage through the pump or turbine. The obvious advantage is that these are fish types and
sizes resident at the site. Further, these fish display natural behaviour as they approach and enter the
intake. Still, it is recommended for most survival tests to use introduced fish because it offers greater
experimental control in terms of sample sizes, species, size classes, and the duration of the tests. The
condition of introduced fish is also known prior to release which allows for an accurate assessment of
passage-related damage, especially if the tests are paired with the release of a control group of fish that
are biologically identical and undergo the exact same handling, release, collection, and holding
procedures as the test fish, with the exception of passage through the pump or turbine.
Netting, balloon tagging, and telemetry are widely used methods to collect or monitor fish after passage.
Of these methods, collection nets are used most because they are versatile and although not cheap, once
in place, allow for a cost-effective assessment of multiple species, size classes, and operating conditions.
If constructed as a so-called full-flow net, covering the entire flow through one or more units, and sealed
properly, it can result in total recovery of released fish. Uncertainty related to fish that are not recovered
is then eliminated. Partial-flow nets lack all these advantages and must be avoided if possible. They
exhibit low recapture rates of released fish and potential intrusion of downstream resident fish.
Consequently, uncertainty levels of mortality rates are high.
Balloon tag and telemetry (radio or acoustic) are alternative methods to assess passage-related fish
mortality. Both have a low initial cost but high unit cost if large numbers of fish are required. For this
reason, such studies often have limited numbers of operating conditions, species and size classes, and
small sample sizes. Tagging fragile species or small fish may come with high handling-induced losses.
Further, tagged fish can be impacted in their swimming ability causing a bias in the results.
In balloon tag studies fish are tagged with a self-inflating tag and released. Contact with water inflates the
tag after a while, buoys the fish to the surface and allows recovery by a boat crew. Telemetry is different
in that fish are not recovered after release. Instead, their movement after passage is monitored. Often
tagged dead fish are released as well to distinguish between the movements of live and dead fish. Injury
and mortality can be detected by monitoring changes in behaviour and lack of active swimming. The
assessment of delayed mortality rates can be hindered by a restricted survey zone and the uncertainty in
classifying live and dead fish may lead to errors.
2. Fish survival tests in the laboratory
Survival tests in a laboratory or a factory share some of the characteristics of tests in an existing plant.
The pump or turbine that is being assessed will have the exact same geometry except it is usually a model
at a smaller scale, operating at a different flow rate and shaft speed. Tests may be done with fish of a
different size class which requires scaling of the results with obvious uncertainties. The risk of
barotrauma in a scale model is different from a full-scale installation. In addition, scale-model test rigs
often do not entail all the components a real plant has, like a forebay with intake structure, a penstock, or
auxiliaries like a trash rack or a gate valve. As a result, survival tests at model-scale are not easily
translated to conditions at the actual plant. Laboratory tests at model scale are typically done during the
development of a new type of pump or turbine design and results need eventual validation at full-scale.
3. Model-based prediction of fish survival
A model-based prediction of fish survival can provide a fair estimate of what is to be expected in reality.
Such predictions are useful in the early stages of a new pump or turbine design before the laboratory
survival tests take place. Water authorities can make use of these models to estimate survival rates of
machines not yet commissioned or compare expected fish survival in existing installations before and
after commissioning. A first quantification of the impact can thus be obtained without the use of live fish.
It complies with the European Directive 2010/63/EU [4] and the aim to replace all animal research with
non-animal methods. The decision to conduct subsequent tests with live fish can be made contingent on
the results of a computational model.
Several models exist that estimate mortality due to blade strike, being the primary cause of damage to
fish passing through many pumps and turbines. These models are usually based on a blade encounter
model to predict the likelihood of a collision between a fish and a blade, followed by an empirical model
to predict the probability of that collision being fatal. The blade encounter model can be replaced by a
Computational Fluid Dynamics (CFD) calculation of the flow through a pump or turbine. The trajectories
of fish, modelled as passive objects moving through the machine, can be calculated and the likelihood of
a blade collision be estimated. These CFD calculations offer the additional possibility to calculate pressure
changes and values of velocity shear along fish trajectories. Yet, no matter how advanced the CFD method
is, the resulting survival rates will still be estimations: trajectories rely on the points of entry, on assumed
mass density of the fish, on fish flexibility and swimming behaviour, and the eventual damage and
mortality relies on correlations with stressors like strike velocity, pressure, and shear rate.
Small installations
In general, when determining the need for fish survival tests, one should inquire whether a pump or
turbine installation constitutes a bottleneck for local or migrating fish species. How many fish are likely
to pass through the installation and are these species considered endangered? In addition, for small
installations, the question arises as to whether it is meaningful to conduct fish survival tests for relatively
large fish in small pump or turbine installations if these fish are effectively excluded from entrance by
screens and trash racks with small mesh sizes. A survival test in which fish are introduced before the
intake but downstream of a screen is likely to provide an unrealistic image of actual mortality.
Guiding principles for survival tests
Animal research in the European Union (EU) is governed by Directive 2010/63/EU [4], which establishes
guidelines for the protection of animals used for scientific purposes. This Directive emphasizes adherence
to the 3Rs principles: replacement, reduction, and refinement, to ensure that animal welfare is prioritized
in all scientific experiments. To align with these principles, researchers must carefully address the
following ethical and practical considerations:
— The necessity and utility of the planned experiment in relation to existing knowledge derived from
prior studies;
— The appropriateness of the selected methods, along with the likelihood of obtaining meaningful and
reliable results;
— The absence of viable alternative methods capable of achieving the same objectives;
— The alignment between the chosen animal models and the scientific objectives of the experiment;
— An assessment of potential harm to the animals compared with the anticipated benefits of the results;
— The biological and cognitive characteristics of the species involved, including their sensitivity and
fragility;
— Ensuring that the selection of species, particularly non-native species, does not pose a threat to
biodiversity;
— Limiting the number of animals used to the minimum necessary to achieve the study’s objectives;
— Maintaining the welfare of trial fish, including decisions around storage and husbandry, to ensure
that their physiological and behavioural characteristics remain unaltered as far as possible before,
during, and after the trial.
Model-based prediction of fish survival and other alternative methods using sensors to measure fish
survival in pumps and turbines may be developed in the near future and could finally replace (or
significantly reduce) direct tests on animals. Meanwhile, experiments requiring animal use are needed
but must be carefully planned and carried out. The rules and guidelines in this standard are aimed at
minimizing the use of test animals as much as possible and maximizing their well-being.
1 Scope
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:
— 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);
— 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.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https://www.iso.org/obp/
— IEC Electropedia: available at https://www.electropedia.org/
3.1
acclimatization
process of allowing fish to adapt to changed conditions in the living environment
3.2
archimedes screw
open or closed screw that can be used as a pump or turbine, able to transport water between different
water levels at ambient conditions
3.3
barotrauma
injury that occurs in fish because of pressure changes, notably a rapid decrease of pressure
3.4
centrifugal pump and turbine
common term for rotodynamic pumps and turbines of the radial, mixed and axial flow-type
3.5
collision probability
P
co
probability that a fish will collide with the leading edge of a guide vane or a rotor blade of a pump or
turbine
3.6
computational fluid dynamics
CFD
computer simulation of a flow of liquid or gas
3.7
control fish
fish of the same species and size class as the test fish, that are in a similar health condition and undergo
identical handling procedures, with the exception of passage through a pump or turbine or a complete
installation
3.8
delayed mortality
mortality that occurs in a predetermined period after the fish survival test
3.9
direct mortality
mortality that is observed immediately after recapture and collection from a collection net
3.10
downstream migrating fish
fish that swims into an installation in the direction of flow of the water
3.11
draft tube
diffuser (i.e. diverging pipe or channel) located downstream of a turbine rotor, where the average velocity
reduces, and the static pressure rises
Note 1 to entry: The outflow diffuser is an integral component of the hydropower plant.
3.12
dynamic head losses
H
dyn
measure of the pressure losses in a flow of water through a pipeline systems leading to a loss of head
3.13
field test
fish survival test of an actual pumping station or hydropower plant on-site, operating under practical
conditions
3.14
flow rate
quantity of water flowing through the pump or turbine per unit time
Note 1 to entry: Also called capacity or volume flow rate.
3.15
guide vane
stationary blade in a pump or turbine to guide the flow of water
Note 1 to entry: A baffle is an example of a guide vane.
3.16
hydropower plant
installation where the energy contained in a flow water (either velocity or a level difference) is converted
to electric energy by means of one or more turbines
3.17
injury
deviation from the natural state of a fish caused by an external force
3.18
injury model
model-based calculation method to estimate injury to fish that pass through a machine
3.19
introduced fish
fish that are released closely upstream of a pump or turbine in a fish survival test, as opposed to naturally-
entrained fish that reside upstream of a pump or turbine
3.20
laboratory test
fish survival test of a pump or turbine in a controlled environment or in a facility set up for test purposes
3.21
manometric pump head
sum of the static head and the dynamic head losses in the piping system
Note 1 to entry: Manometric pump head is the head difference across the pump.
3.22
manometric turbine head
static head minus the dynamic head losses in the piping system
Note 1 to entry: Manometric turbine head is the head difference across the turbine.
3.23
meridional plane
cross sectional plane in a pump or water turbine where the rotation axis of the rotor forms part of the
plane
3.24
migration
movement of fish between various water systems and habitat types to spawn, feed, escape, or rest
3.25
mortality
P
m
probability a fish suffers lethal injury while undergoing a specific treatment
3.26
mutilation ratio
f
MR
probability that a strike with a blade will lead to serious fish injury
3.27
Open-water turbine
turbine without scroll or inlet guide vanes, in which the kinetic energy of the approaching flow of water
is converted to mechanical energy in the runner where the runner blades rotate at some distance from
the housing, or where there is no housing
Note 1 to entry: Also called a free-flow turbine, freestream turbine, or hydrokinetic turbine.
Note 2 to entry: Open-water turbines are positioned in a flow of water, either at a certain depth below the water
surface or in a duct which is wider than the diameter of the turbine, such that approaching fish may passively or
actively avoid the rotating turbine runner.
3.28
passage survival
probability a fish survives passage through a pump or turbine. This is assessed in a passage survival test
3.29
penstock
piping at the high-pressure side of a turbine
3.30
pumping station
installation where surface water is transported, usually to a higher level, by means of one or more pumps
3.31
rotor
rotating part of a pump or turbine
Note 1 to entry: A rotor is also called an impeller, runner, or propeller.
3.32
Secchi distance
depth at which a disk lowered into the water can no longer be seen from the surface
Note 1 to entry: The Secchi depth is related to water clarity and is a measure of how deep light can penetrate the
water. It is used as an estimate of the distance over which a fish can detect an object.
3.33
serious fish injury
injury that leads to direct mortality in fish or to (expected) mortality in the longer term
Note 1 to entry: In this standard serious fish injury is assessed as mortality.
3.34
shaft speed
revolution speed of a rotor, measured as the number of rotations per unit time
3.35
shear
velocity gradient normal to the direction of the flow
3.36
silver eel
mature eel of a silver-grey colour that travels from inland water to the sea in order to reproduce
3.37
smolt
young salmon or young trout one or more years of age that migrates from fresh waters to the sea
3.38
static head
H
st
difference in water level on both sides of a pump or turbine installation, also called system head
3.39
strike velocity
velocity of a fish relative to the leading edge of a guide vane or blade, at the moment of strike
3.40
suction pipe
piping at the low-pressure side of a pump
3.41
survival
probability a fish survives while undergoing a specific treatment.
Note 1 to entry: Also called survival rate or survival probability
Note 2 to entry: The survival is also expressed as (1 – mortality P ).
m
3.42
passage survival test
test in which the survival of a group of test fish is assessed and corrected with the survival of a group of
control fish, to obtain the passage survival probability.
3.43
test fish
fish of a specific species and size class that undergo introduction and passage through a pump or turbine,
and subsequent recapture in a collection net
3.44
test scenario
combination of fish species and size class, and operating conditions of a pump or turbine
3.45
trash rack
coarse screen to catch debris floating or suspended in the water, such as plants, duckweed, (cutting)
waste and wood, that also serves to protect the machinery
Note 1 to entry: A trash rack also has the function of protecting people and animals.
3.46
trash rack cleaner
machine that automatically or otherwise removes the floating and suspended debris from the trash rack
and dumps it on dry land
3.47
upstream migrating fish
fish that swims into an installation against the direction of flow of the water
4 Drawings of the installations
Figures 1 to 7 in this clause show schematic drawings of typical pumping stations and hydropower plants
highlighting key, generic components of such installations in general.
Key
1 trash rack
2 trash rack cleaner
3 suction chamber / intake
4 volute
5 mixed-flow pump impeller
6 flow splitting wall
7 crane
8 motor
9 discharge
10 gate
11 non-return valve
Figure 1 — Schematic view of a pumping station with a mixed-flow pump
Key
1 trash rack
2 trash rack cleaner
3 suction chamber / intake
4 flow splitting wall
5 axial-flow pump impeller
6 diffuser
7 crane
8 motor
9 butterfly valve
10 vacuum relief valve
11 syphon
Figure 2 — Schematic view of a pumping station with an axial-flow pump
Key
1 trash rack
2 trash rack cleaner
3 intake
4 Archimedes screw pump
5 motor
6 discharge
7 non-return valve
Figure 3 — Schematic view of a pumping station with an Archimedes screw pump

Key
1 trash rack
2 sluice gate
3 intake
4 power house
5 generator
6 Archimedes screw turbine
7 discharge
Figure 4 — Schematic view of a hydropower plant with an Archimedes screw turbine
Key
1 headwater
2 trash rack
3 intake
4 gate
5 penstock
6 power house
7 generator
8 Francis turbine runner
9 guide vanes/wicket gates
10 scroll
11 draft tube
12 tailwater
Figure 5 — Schematic view of a hydropower plant with a Francis turbine
Key
1 headwater
2 trash rack
3 trash rack cleaner
4 intake
5 crane
6 power house
7 generator
8 Kaplan turbine runner
9 guide vanes/wicket gates
10 scroll
11 draft tube
12 gate
13 tailwater
Figure 6 — Schematic view of a hydropower plant with a Kaplan turbine
Key
1 headwater
2 trash rack
3 trash rack cleaner
4 intake
5 crane
6 power house
7 generator
8 inlet guide vanes
9 Kaplan or propeller turbine runner
10 gate
11 discharge
12 tailwater
Figure 7 — Schematic view of a run-of-river hydropower plant with a bulb-turbine
5 Equipment and tools
5.1 Collection net
A collection net is used to recapture fish after passage through the pump or turbine. The net is designed
as a full-flow collection net to sample the entire flow from a pump or turbine unit. Construction shall aim
at the full recapture of fish passed through the machine and at preventing intrusion of fish residing in the
body of water downstream of a turbine or a pump. Additionally, care should be taken to ensure that any
fish residing or hiding in the outflow area of the pump or turbine are removed before installing the net,
to avoid unintended inclusion in the sample or interference with the collection process.
The dimensions of the net and the size and type of the mesh have an influence on the collection efficiency
and the extent of injury it can cause to fish. It shall meet the following requirements:
— the net is made of knotless material to reduce abrasion of collected fish;
— the net is big enough (i.e. have sufficient net area) to have low through-flow velocity and thus prevent
impingement of fish and related injury;
— the mesh size is tailored to the sizes of collected fish to prevent fish escapement or injury. For
instance, for smolt size fish a mesh size of 18 mm stretched mesh can be used;
— it is possible to remove fish easily and without injury from the collection net.
In addition:
— the net is big enough for fish to move away from the discharge stream and seek refuge in areas of low
velocity,
or
— a floating collection box, live well, or keepnet is attached to the end of the collection net, large enough
to provide adequate shelter from high velocities and turbulence.
Preferably, the net should be closed from above to prevent predation by birds.
If, during field tests, a lot of debris enters the net, a larger net area or a larger mesh size may be required.
If a full-flow collection net cannot be applied on site, balloon-tagging of test and control fish may be
considered as the next best recapture alternative.
5.2 Fish introduction device
A piping system to introduce fish into a pump or turbine installation with minimum risk of damage. The
introduction device is designed and built to fit the dimensions of the intake structure and the largest size
class of fish in the survival test.
All pipe surfaces are finished, edges are rounded, and contractions or expansions in pipe diameter are
gradual. Pipe connections are flush on the inside. Protruding parts are avoided.
After insertion at the entrance, fish are flushed through the pipe by a secondary flow of water from a
pump or auxiliary tank. A large-radius pipe bend redirects and aligns the fish parallel with the flow in the
intake structure. The flush water capacity should ideally match the local velocity in the intake at the point
of release, which usually is around 1 m/s. Higher velocities may be selected for good swimmers, like
salmonids.
Figure 8 shows an illustration of a safe fish introduction device. Figure 9 shows how fish are being
introduced.
Key
1 inflow of secondary water
2 fish insertion
3 bend (≤90°)
4 release of water and fish
Figure 8 — Illustration of a fish introduction device, top and side view

Figure 9 — Example of fish introduction
5.3 Transport tank
Tank used for transporting fish over large distances.
Recommended fish density: ≤ 20g of fish per L of water. Has continuous oxygen supply and discharge of
toxic gases. May include a water circulation system to maintain oxygen levels and water temperature, as
well as a means to monitor and control these conditions.
5.4 Storage tank
Tank, closable or coverable, where fish are held before and during the survival test.
The volume of the tank depends on the number and the size of fish. Recommended fish density: ≤ 20g of
fish per L of water. Each tank has continuous oxygen supply and discharge of toxic gases. May include a
water circulation system to maintain oxygen levels and water temperature, as well as a means to monitor
and control these conditions.
NOTE 1 Eel can be stored at larger fish densities, e.g. 60 g/L.
NOTE 2 Test and control fish can be held in separate tanks but under the same conditions (water quality, fish
density).
5.5 Keepnet
Net used to temporarily hold and store fish, designed to allow water to flow through it, keeping the fish
alive while they are in the net. It should be placed in slowly flowing se
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