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1. ENVIRONMENTAL FLOW
AND
FISH PASSES
SHAHANA S
FRM-PB0-04

2. INTRODUCTION
• ‘Conservation of ecosystems as a public good, independent of their utility as a
resource’ was the main promotion of Earth Summit(1992)
• A logical extension is to grant water rights to the species and ecosystems
• Enormous economic importance of ecosystem functions and services to mankind is
highlighted(Coastanza et al.,1997 & Postel and Carpenter,1997)
• World Water Forum(2000) paid first attention in the he role of sustainable water
resources management in ensuring the integrity of ecosystems
• Environmental protection is the key pillar of sustainable development (World
Summit, 2002)
• Environmental flow is one of the main concepts considered as the key element of
integrated water resource management.

3. ENVIRONMENTAL FLOW
• Environmental flows (EFs) are flows left in or released into a river system with the objective
of managing particular aspects of the river ecosystem
• Efs are the flows to be maintained in the river for its healthy functioning and the sustenance
and protection of aquatic ecosystems
• Water flow regime that has been designed and implemented through release of water from
an impoundment into the immediate downstream of a river so as to achieve desired
ecological conditions and ecosystem services
• EFs target the main river channel and its surface waters, groundwater recharge, estuary of
the river, associated wetlands or floodplains, the riparian zone or any plant and animal
species associated with these ecosystems
• EFs involves the quantity, timing, duration, frequency, and quality of flows required to
sustain freshwater, estuarine and near shore ecosystems and the human livelihoods and
their well-being that is dependent on them

5. WHAT DOES IT DO?
 To purify itself
 Sustaining aquatic life and
vegetation
 Recharging groundwater
 Supporting livelihoods
 Facilitating navigation
 Preserving estuarine
conditions
 Preventing the incursion of
salinity
 Cultural and spiritual lives of
people
Importance of environmental flow regime (EFR)

6. Recognition of the escalating
hydrological alteration of rivers
on a global scale and resultant
environmental degradation
ESTABLISHMENT OF THE SCIENCE
OF ENVIRONMENTAL FLOW
ASSESSMENT
• Diminution of riverine ecosystem is one of the major challenging issues.
• These alterations in river flow is mainly due to the
Construction of storage
Diversion
Control structures
which are primarily for
Generation of electricity
Irrigation
Flood control
Baghel et al.,2018
No. of dams in world based on their purpose. Source:http://www.icold-
cigb.org/GB/world_register/general_synthesis.asp
WHY ENVIRONMENTAL FLOW ASSESSMENT?
A compromise between water resources development and
maintenance of a river in an agreed / prescribed condition

7. Classifications for
ENVIRONMENTAL FLOW ASSESSMENT METHODOLOGY
(EFAM)
• International Union for Conservation of Nature
(IUCN)
1. Methods
2. Approaches
3. frameworks
• World Bank Classification
1. perspective
2. interactive
International Water Management Institute (IWMI)
Classification
1. Hydrological Methods
2. Hydraulic Rating Method
3. Habitat Simulation Method
4. Holistic Method
Flowchart of environmental flow

8. IWMI CLASSIFICATION

9. Hydrological Methods (HM)
 Based on the analysis of historic stream flow data and do not work at a species specific
level.
 The basic approach is that the more quantity of water will provide the best way
• Specific portion of the average annual flow (AAF), equivalent to mean annual
flow(MAF), is required to preserve the biological integrity of a river ecosystemTennant Method
(Montana method)
• An analysis based on graphs developed between historical stream flow
variations and time durations
• It derives percentage equaled or exceedance values of a particular discharge
for given time variations
Flow Duration
Curves (FDCs)
• Assesses flow regime alterations by comprehensive statistical analysis of
ecological parameters.
3.Range of
Variability Approach
(RVA)

10. Hydraulic Rating Method (HRM)
• Habitat retention or hydraulic geometry methods is derived through the interrelationship of hydraulic
parameters of a river and its discharge.
• Integrates the flow data with hydraulic parameters obtained from the site over river cross section
obtained from the site over river cross section
• simplest and dependable method since it has clear concept
mathematics of finding the critical point on the curve between
wetted perimeter and stream flow.
• Optimum discharge, usually for fish spawning or highest
production by benthic invertebrates, is generally identified from a
discharge near the critical point of thewetted perimeter-discharge
curve
Wetted Perimeter
Method

11. Habitat Simulation Method (HSM)
 Method incorporates hydraulic rating with the preferential habitat characteristics of the
target species.
 Biological sampling of indicator species is used to populate the habitat part of the
model.
 Hydraulic and biological are merged into a single model, and the resultant model is
used to determine the preferential area for the target species at various flows, and
further will help to deduce the required flows
• works in four stages dealing with various things such as details about the
stakeholders, type of scale, data collection
• At the last stage, all these components are integrated to give the appropriate
environmental flow
Instream Flow
Incremental
Methodology (IFIM)
• A major component of IFIM is a suite of computer models
• incorporates hydrology, stream morphology and microhabitat preferences to
generate relationships between river flow and habitat availability
Physical HABitat
SIMulation model
(PHABSIM)

12. Holistic Methods
consider all biotic and abiotic components present in the river ecosystem along with
other associated water bodies instead of focusing on a few characteristics and
livings
• segregates the flow regime of a river into components in terms of their
timing, duration, frequency and magnitude (Building Blocks)
• Flows characterized into dry-season base flows (low flows), wet-season
base flows, wet-season floods, dry-season freshes and dry-season
subsurface flows
• The modified flow regime is obtained by combining the building blocks
in a manner that it mimics the virgin flow regime
Building Block
Methodology
(BBM)
• utilizes monthly flow data and separates the total flow into high flows and
low flows during ‘‘normal years’’ and ‘drought years’’.
• uses two quantities to represent the hydrological variability: the
Hydrological Index representing climatic variability, and the Base Flow Index
(BFI; proportion of base flow to the total flow)
Desktop Reserve
Model (DRM)

15. DETAILED, PARTICIPATORY METHODS
Upper Ganges, upstream of Kanpur
(WWF-India – IWMI - IHE and other partners)
The four zones were chosen to represent the following
conditions:
Zone 1. A mountainous sub-stretch -Gangotri to Rishikesh
Zone 2. A sub-stretch (or zone) which is relatively intact- ( A
reference zone) from upstream of Garhmukteshwar
to Narora
Zone 3. A sub-stretch (or zone) which is affected by water
abstraction through barrage-Narora to Farrukhabad
Zone 4. A sub-stretch (or zone) which is affected by pollution-
Kannauj to Kanpur

16. Assessment of Environmental Flows for the Upper Ganga Basin
• The report strongly recommends the Building Block Method (BBM) for assessment of
E-Flows as “robust and scientifically most suitable”
• The methodology involves identification of keystone species for the river stretch for
which E-flows is to be assessed, after defining the river cross section and generating
stage-discharge curve
• The report defined Keystone specie as: “A species that has disproportionately large
effect on the environment relative to its abundance.”
• In case of Upper Ganga basin, the report identifies two keystone species at different
locations, namely Snow Trout and Golden Mahseer

17. EF SUMMARY, ZONE 1: GANGOTRI- RISHIKESH
maintenance flows
EF SUMMARY, ZONE 3: NARORA –
FARRUKHABAD
maintenance flows
COMPREHENSIVE (BBM) & PLANNING (GANGES CALCULATOR)RESULTS

18. Technology as an Aid in EFA
“A new EFA technique is used to assess the suitability of fish habitat with respect
to synthetic hydraulic and water quality parameters using Takagi–Sugeno fuzzy
logic”
Use of optimization technique and EF management model to calculate optimal
flow and iSTREEM model to evaluate dilution factors in different flow conditions
also give positive results
GIS Satellite HEC Winxspro IHA
USGS
tools
Global environmental flow
calculators
Flow
Health
SOFTWARES eWater Source
• River Analysis
Package (RAP)
• eflow predictor
• Eco-Modeller
• TREND,
• The Invisible
Modeling
Environment
(TIME) etc…….

19. CHALLENGES
o Hydrological methods: the historic flow data are
scarcely available and are inconsistent.
• HRM: braided nature of Indian rivers, and thus, the
hydraulic characteristics of the river such as depth
and wetted perimeter could not be obtained
• HSM: an intensive data such as habitat data at
various sections and suitability data for the
endangered species
• Holistic approach: extensive physical, biological and
ecological analysis for the entire stretch
SOLUTIONS
 the use of different data simulation software such as
RIBASIM, SWAT, which is capable of generating data up
to past 100 years.
 Wetted perimeter method is very simple and works well
with these generated hypothetical data
 Using multi-criteria decision making approach
 Use of eWater tool in calculating hydraulic characteristics
of river.
 Releasing enough water in the river to maintain a single
channel of flow
 Conduct an exclusive biological research, for habitat
study, for all major rivers of the country
 Guidelines of MOEF for hydropower projects which
highlight EF and mandate study of parameters, namely
water quality in basin, status of ecosystem and hydrology
IN INDIAN CONTEXT,
“Use of softwares such as FLOW HEALTH which utilizes monthly flow data, it is easy to assess EF
For indian rivers having inconsistent data series”

20. SUMMARY
• EF- is a tool to maintain a river in an agreed condition. EF need to mimic
natural flow variability
• A combination of simple (planning) and comprehensive (holistic) EF
assessment tools is ideal for EF management. The levels of accuracy and
confidence differ, but both types of tools have distinct purposes.
• A number of EF tools and information, freely available, are already
developed for India - for further use and refinement with Indian partners
and responsible agencies
• Studies were normally carried out in the conditions of lack of access to
hydrological and hydraulic data.
• Actual EF provisions are not the same as estimated EF. No matter how
advanced and accurate the estimates are, its output remains on paper if
no actual implementation is made. It needs Policy and Institutional
support.

21. “Fish passes are the only option to conserve
migratory fishes if the retention of minimum
environmental flow regime cannot be attained while
constructing the barriers across the natural lotic
aquatic habitats”

22. FISHPASSES
• Most fish species develop movement and migration behaviours in
order to complete their biological functions.
• Depending on the species and the nature of the function, these
movements and migrations occur at different times, distances and
directions
• Many rivers are deteriorated by anthropogenic activities with major
impacts on the river continuity, the flow, the hydromorphology and
the thermal regimes
• Restoration of longitudinal connectivity in an upstream direction
using different fish-pass models is the most frequent remediation
measure because the re-establishment of upstream reproductive
migration is often considered a priority(Roscoe and Hinch 2010).

23. • Many fish species undertake more or less extended
migrations as part of their basic behaviour
• Amongst the best known examples are salmon
(Salmo salar), Tenualosa ilisha and sturgeon
(Acipenser sturio), which often swim several
thousands of kilometres when returning from the sea
to their spawning grounds in rivers
• Other than long distance migratory species, other fish
and invertebrates undertake more or less short-term
or small-scale migrations from one part of the river to
another at certain phases of their life cycles
Tenualosa ilisha
Anguilla bengalensis
Salmo salar

24. A review on impacts Cross-river obstacles on Indian fisheries
• Construction of Mettur Dam on the Cauvery River completely stopped runs of the
Indian shad, Tenualosa ilisha (Sunder Raj, 1941)
• Construction of Salandi dam in Odisha resulted in decline in the annual catch of the
main species from 350 tonnes/annum (1950-65) to approximately 25
tonnes/annum (1995-2000) in the river reach
• Construction of Ithai barrage in India for hydroelectric project has disturbed the
migratory Osteobrama belangeri from Chindwin in Myanmar to Loktak Lake thus fish is
extinct in the wild and there is no possibility of recolonization from Myanmar (CAMP,
1998)
• After construction of Tawa and other projects, the Mahseer catches at
Hoshangabad have already dropped drastically (Arya et al., 2001)

25. Contd…
• Construction of a dam on Beas river has resulted in decline in proportional winter fish
catch of mahseers and schizothoracines between Mandi and Nadaun from 10.2 to 13.5 %
in year 1964 to 1.0 – 0.5 % in year 1985-87 (Sehgal, 1999)
• Obstruction by Beas dam has limited the upstream migratory ascend of Tor putitora to
Pandoh (Sehgal, 1990)
• Sharma (2003) has found that construction of Tehri dam in Uttarakhand has considerably
reduced the water flow and have shown detrimental effects on feeding, spawning, and
migration routes of mahseer
• Lakra et al. (2010) reported the considerable loss of fish species in the downstream of
Betwa River due to damming and resulting fragmented river channel. The dam in this river
prevents migratory fishes such as Tor tor, Bagarius bagarius, Pangasius pangasius,
Silonia silondia and Sperata aor

26. Hilsa landings in Ganga upstream of Farakka
Barrage
Pathak et al., 2010
The drastic decline in the hilsa landing from the stretch of river Ganga
above Farakka barrage is a result of obstruction of hilsa runs by the
barrage

27. THAT IS WHY FISHPASSES….
• Fish passes are of increasing importance for the
restoration of free passage for fish and other
aquatic species in rivers
• Fishways can be constructed in a technically
utilitarian way or in a manner meant to emulate
nature.
• Bypass channels and fish ramps are among the
more natural solutions
• The more technical solutions include conventional
pool-type passes, slot passes, fish lifts, hydraulic
fish locks and eel ladders.

28. General requirements for fish passes
A. Optimal position for a fish pass
B. Fish pass entrance and attraction flow
C. Fish pass exit and exit conditions
D. Discharge and current conditions in the fish pass
E. Lengths, slopes, resting pools
F. Design of the bottom
G. Operating times
H. Maintenance
I. Integration into the landscape

29. A. Optimal position for a fish pass: The most suitable position for a fish pass at hydroelectric power stations is usually on the
same side of the river as the powerhouse (FAO, 2002)
General requirements for fish passes
B. Fish pass entrance and attraction flow
C. Fish pass exit and exit conditions:
• Exit into the headwater must be located far enough
from the weir or turbine intake so that fish coming
out of the pass are not swept into the turbine by
the current
• A minimum distance of 5 m should be maintained
between the fish pass exit and the turbine intake
• If the current velocity of the headwater is greater
than 0.5 m s-1, the exit area of the fish pass has to
be prolonged into the headwater by a partition wall

30. D. Discharge and current conditions in the fish pass:
• The discharge required to ensure optimum hydraulic conditions for fish within the pass
is generally less than that needed to form an attracting current
• Current velocity in fishways should not exceed 2.0 m s-1 at any narrow point and this
limit to velocity should be assured by the appropriate design of the pass
At the side of impoundment, several water inlets (fish
exits) at different level guarantee that fish can leave the
pass even at varying headwater levels

31. E. Lengths, slopes, resting pools:
• The average body length of the largest fish species expected in the river as well as the
permissible difference in water level must be considered in defining the dimensions of a
fish pass
• The water level difference between pools in a fishway be also kept below 0.2 m
• The maximum permissible slope ranges from 1:5 to 1:10, depending on the construction
principle chosen
• The swimming ability of the fish species of the potential
natural fish fauna and all its life stages has to be
considered in setting the length of a fishway
• Resting pools where turbulence is minimal should be
inserted at intermediate locations (Figure) into types
of fishways that have normally no provision for resting
Zones due to their design

32. F. Design of the bottom:
The bottom of a fish pass
should be covered along its
whole length with a layer at
least 0.2m thick of a coarse
substrate
G. Operating time:
• Must operate throughout the year.
• Limited operation can be tolerated only during extreme low- and high water
periods since at such times fish usually show a decrease in migratory activity
H. Maintenance:
• The need for regular maintenance must be considered from the start of planning a
fish pass as poor maintenance is the chief cause of functional failure in fishways
• Obstruction of the exit of the pass (i.e. the water inlet) and of the orifices, damage
to the fish pass structure or defective flow control devices are not rare but can be
overcome through regular maintenance
I. Integration into the landscape:
• Every effort should be made to integrate the fish pass into the landscape as
harmoniously as possible, although the correct functioning of the fishway must
take priority over landscaping.
• Natural building materials or construction materials that are typical of the local
conditions should be used in the construction of fishways in a consequent manner

33. TYPES OF FISH PASSES
Types of fish passes
Close to nature type
Bottom
ramps &
slopes
Bypass
channels
Fish
ramps
Hydraulic
designs
Technical fish passes
Pool pass Slot pass
Denil
pass
Eel
ladders Fish lock Fish lift

34. River
Name of
the weir
Year of
construction
(fish ladder)
Design/Specifications
Fish species
encountered
Sutlej
Ropar
1882 – 1st
1921 – 2nd
Two fish ladders. The left ladder originally had 14 bays and
an additional bay was added in 1914 – 15. The right ladder
had 10 bays to begin with and additional compartment
added on 1926 – 27, with further modifications in 1927 –
28.
Aspidoparia
morar, Wallago
attu, Clupisoma
garua and
Mahseers
Ferozepore 1927-29
A single fish ladder consisting of 18 bays with incomplete
baffle walls. The dimensions of the bays are 3 feet by 4
feet with a fall of 6 inches in each.
A. morar, Labeo
microphthalmus
Suleimanki 1926
Two fish ladders. The right ladder (308 feet long) consists
of 24 bays with incomplete walls. Left ladder is built on
inclined plane system.
A. morar,
Eutropiichthys
vacha, Labeo
rohita, L. calbasu
and Cirrhinus
mrigala
Islam 1930
Single fish ladder (total length of 355 feet) consisting of 10
bays with trapezoidal shape, each measuring 10 feet by 8
feet.
Panjnad 1931
Single fish ladder with 20 bays (each measuring 7 feet by 8
feet) having incomplete baffle walls.
Khan (1940)
Fish ladders of the Punjab Province on weirs along River Sutlej

35. River Name of the weir
Year of
construction
(fish ladder)
Design/Specifications
Ravi
Madhopur 1928
Single fish ladder consisting of 17 bays with complete
baffle walls, each having an opening of 2 feet wide for
passage of fish.
Balloki 1921
Single fish ladder (127.05 m long) consisting of 17 bays
with baffle walls, each having an opening of 2 feet wide
for passage of fish.
Chenab
Marala 1910
Single ladder built on the inclined plane system. There
are 6 compartments, each measuring 12 feet by 10 feet.
Khanki
First ladder in 1912
– 13. Dismantled
and substituted by
new one in 1934 -
35
Single 203 feet long fish ladder consisting of 16 bays
with incomplete baffle walls. Constructed on improved
Cail fishway system. No fish has ever been reported to
use this ladder.
Jhelum
Rasul 1901
Single ladder consisting of 7 bays with incomplete baffle
walls leaving an opening of 3 feet width for the passage
of fish. Occasionally used by small sized species such as
A. morar.
Fish ladders of the Punjab Province on weirs along Rivers – Ravi, Chenab and Jhelum
Khan (1940)

36. STATUS OF FISH PASS IN INDIA
• Limited fish pass facilities were provided in the dams constructed on the rivers, Ganges,
Yamuna, Mahanadi, Jhelum and Teesta only during post-independence
• Fish pass facilities installed in India during recent times can be broadly categorized in to
four – pool pass, Denil pass, fish ramps and fish locks
• ICAR-CIFRI have been instrumental in carrying out feasibility studies regarding installation
of fish passage structures in Indian dams
• The recommendations were considered for developing fish passage facilities in India at
Farakka in the Ganges, Bichum dam in Arunachal Pradesh and Teesta Low Dam stages III
and IV on Teesta River in West Bengal
• No detailed information on efficacy of fish pass facility at India is available
• Currently, ICAR-CIFRI is carrying out efficacy study of fish pass installed at Teesta Low
stage Dam III & IV

37. Fish lock facility at Farakka barrage
• No comprehensive studies on passage performance is
available
• Presently the fish lock facility is not in operation so deemed
non functional
• Studies conducted by ICAR-CIFRI has revealed that collapse
of Hilsa fisheries upstream Farakka

38. Pool passes at Teesta Low Stage Dam III and IV
•No comprehensive studies on passage performance is available
•This is being operated by National Hydro-electrical Power
Corporation
•Presently efficacy study of fish pass is being carried out by
ICAR-CIFRI, Barrackpore

39. Denil pass at Naraj Barrage
Denil pass at Mahanadi Barrage
Occurrence of hilsa shad during rainy
season at Mundali (7 km upstream of
Jobra/Mahanadi barrage), Ramdashpur
and further upstream was an indication
of the possible upstream migration
through fish passes (Das and Hassan,
2008

40. Denil pass at Hathnikund Barrage
The pass provides safe upstream passage to the Mahseers and other carps which is migrating
upstream through 8 falls provided in the Western Yamuna Canal ( Das and Hassan, 2008)

41. Details of proposed pool pass at Bichum dam

42. Fish ramps
• Principle-Ramps with gentle slopes and a rough surface; integrated into the
weir structure. Their body may be of rockfill, with boulder sills to reduce
flow velocities
• Applicability-Used at fixed weir sills, and at multi-bay weirs as a substitute
for a weir bay. They are not suitable for variable impounding heads
• Effectiveness-They are passable for all aquatic fauna in both directions, i.e.
upstream and downstream.

43. FISH RAMP

44. Fish locks
• Principle-A pit-shaped chamber with controllable closures at headwater and
tailwater openings. The attraction current is formed by controlling the sluice
gate openings or by sending water through a bypass.
• Applicability-Used for high heads, and where space or available water
discharge is limited.
• Effectiveness-According to present knowledge, suitable for salmonids and fish
with weak swimming capacities. Less suitable for bottomliving and small fish.

45. FISH LOCK AT FARAKKA BARRAGE

46. Pool passes
• Principle-Are generally concrete channels with cross-walls of wood or
concrete which are fitted with submerged orifices and top notches on
alternate sides
• Applicability-Used for small and medium heads, at melioration dams and at
hydroelectric power stations
• Effectiveness-Suitable for all species of fish if the dimensions of the pools
and orifices are chosen as a function of the fish size that can be expected to
occur. There might not be sufficient attraction current at low discharges.

47. Pool pass

48. Denil pass
• Principle-Wooden or concrete channel with sectioned baffles (usually
of wood) that are U-shaped, and are set at an angle of 45° against the
flow direction.
• Applicability-Suitable for small heads, particularly for retrofitting of
old milldams when there is not much space.
• Effectiveness-According to present knowledge, less suitable for weak
swimmers or small fish. Selective. Benthic fauna cannot pass.

50. Methods for fish passage performance studies
1. Conventional Fish trapping
2. Electrofishing
3. Video-recording and auto counting machine
4. Mark and recapture
5. Visual Observation
6. Eco sounding
7. Telemetry

51. Sl. No. Types of factor Factors
1 Hydrological Flow and discharge, water temperature, turbulence and drag
2 Structural Design, distances between resting areas, depth of water column, in pass
attraction features, % slope
3 Biological Size of tagged individuals, Sex of individuals, Species, swimming
performance of fish species-size-sex (slip velocity, burst velocity), Post
tagging recovery physiological condition and motivation, diurnal behaviour
and genetic differences among individuals.
FACTORS AFFECTING THE PASSAGE PERFORMANCE

52. SUMMARY
• Fish passes are structures (natural or manmade) bypassing barriers (e.g.,
dams), enabling satisfactory movement of migratory fish species
• Reestablishment of fish passage, including facilitating overcoming barriers
presented by impoundments
• Restoration of defunct structures, is attracting interest among scientists and
policymakers as a mechanism to enable recovery of target fish species or fish
communities
• Studies of existing devices have shown that many of them do not function correctly.
• Various stakeholders should come together to give a valid design criteria and
instructions that correspond to the present state-of-the-art of experience and
knowledge.

53. REFERENCES
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55. THANKYOU…..