Water Power and Dam Construction. Issue October 2010
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WWW.WATERPOWERMAGAZINE.COM OCTOBER 2010 31
SPILLWAYS
construction was completed at the end of 2006, the investigations on
the morning glory spillway in the middle of 2007.
HYDRAULIC SCALE MODEL
A prototype reservoir area of about 10,000m
2
, a portion of the right
valley ank and the spillway structures of the Val Noci dam were
reproduced in a 1:25 physical scale model using Froude similitude
(see gure 3). Although this similitude guarantees adequate reproduc-
tion of the prototype conditions in the model, accurate modelling of
all hydraulic parameters with the same hydraulic model is impossible.
For example, scale effects related to the water viscosity and surface
tension are signicant on the discharge capacity at small overow
depths. In the present experiments scale effects are negligible for pro-
totype overow depths higher than 0.55m, ie for morning glory dis-
charges exceeding 22m
3
/sec.
INITIAL DESIGN
Layout
The initial design of the morning glory spillway consisted of the fol-
lowing (see gure 4):
r i) A cup-shaped overow structure (transition tube) with a crest
elevation at 537.5m asl, and a crest diameter of 8m, designed for an
overow head of 1.2m and approximately representing a Creager
prole.
r ii) A 32.04m high vertical shaft, 2m in diameter, connected to the
overow structure at 530m asl (throat of the transition tube).
r iii) A circular bottom bend with a radius of curvature of 4m.
r iv) A 26.84m long spillway tunnel, 2m in diameter and with a slope
of 1.6%, joining the existing middle outlet tunnel at an elevation of
492.52m asl. The initial design did not include any aeration device.
DISCHARGE CAPACITY
For reservoir levels up to 538.75masl, the ow is governed by the
crest discharge characteristics, ie the discharge over the morning
glory overow structure can be expressed as
where C
d
is the discharge coefcient, R=4m the crest radius and H
denotes the overow head. According to the service regulation, the
chute spillway is fully opened for reservoir levels above 538.2m asl.
At this water level the chute spillway discharges 150m
3
/sec.
For this case, a strong current towards the chute spillway inu-
ences the approach ow to the morning glory spillway, resulting in
a slightly decreased discharge capacity and a diminished value of
C
d
=0.468, compared to the hypothetical scenario with the chute
spillway out of operation (gure 5). The value of C
d
=0.468 results
from interpolation of measured data. For reservoir levels above
538.75m asl the overow crest is submerged and the entire morning
glory spillway operates under pressure. Therefore, the ow control
section changes from the crest to the downstream end of the spill-
way tunnel. During a pressurised ow regime even a considerable
increase of the reservoir water level leads to only an insignicant
gain in spilling capacity.
FLOW CONDITIONS AND PRESSURES IN THE VERTICAL SHAFT
Annular ow in the overow structure occurs up to a discharge of
approximately 40m
3
/sec. The overow nappe clings to the invert of
the cup-shaped overow structure and a free air core remains in the
centre of the vertical shaft. As the discharge increases, the overowing
annular nappe becomes thicker and converges into a solid vertical jet
at the crotch point. The air-water ow chokes the vertical shaft and
free air entrainment is prevented.
The ow regime changes from free to pressurised ow conditions
and a so-called ‘boil’ forms above the crotch point. Both the boil and
the crotch rise progressively higher for increasing discharge. Due to
the high available net head and the absence of free surface aeration,
sub-atmospheric pressures are measured at the throat of the transition
tube. Due to the lack of a throttle in the hydraulic system, the vertical
shaft is exposed to negative pressures close to the vapour pressure for
discharges of approximately 50m
3
/sec.
At higher discharges, up-scaled pressures at the throat of the tran-
sition tube drop below vapour pressure resulting in a phase change
from water to vapour, ie the water column separates. Therefore, the
ow is governed by this section and the available net head is strongly
reduced, resulting in a restricted discharge capacity.
For a theoretical net head of 45.23m between the reser-
voir water level (538.73m asl) and the tunnel axis elevation
just upstream of the junction with the middle outlet tunnel
(493.5m asl), a calculated discharge of 72m
3
/sec results from
the Bernoulli equation. The corresponding energy and pres-
sure gradients are shown in gure 6. The calculated relative
minimum pressure of –19.4mWC (meter water column) at the
Initial design
8.00m
537.50
2.00m
530.00
497.96
R = 4.00M
498.83
2.35m
530.00
537.50
R = 4.70M
2.00m
492.96
p =
1.6%
492.95
8.35m
28.24m
Circular bottom bend Spillway tunnel
p =
1.6%
2.35m
492.52
Overflow piers
Cup-shaped overflow structure
(transition tube)
Final design
Throat of transition tube
Vertical shaft
Circular bottom bend
with throttle
Junction with the
middle outlet tunnel
2.35m
Figure 3: (a) Downstream view and (b) upper tank of the 1:25 scale model with
(1) reservoir, (2) dam portion, (3) chute spillway, (4) bottom outlet, (5) middle
outlet inlet valve, (6) cup-shaped overflow structure of the morning glory spill-
way, (7) service building, (8) middle outlet tunnel, (9) transition channel, (10)
stilling basin, (11) riprap apron and (12) portion of the Noci valley Figure 4: Layout of both the initial and the final design of the morning glory spillway
32 OCTOBER 2010 INTERNATIONAL WATER POWER & DAM CONSTRUCTION
SPILLWAYS
throat of the transition tube agrees well with the measured and
up-scaled value of –19.5mWC.
The phenomenon of water column separation could not be repro-
duced in the hydraulic model, as Froude similarity would theoreti-
cally require a reduction of the atmospheric pressure in the model.
The maximum prototype discharge of the initial design of the morn-
ing glory spillway has been calculated theoretically. If it is assumed
that the pressure at the throat of the transition tube is equal to
vapour pressure and full pipe ow conditions occurring in the ver-
tical shaft, a discharge of 58m
3
/sec results. For this discharge, the
water column would separate, ie the discharge capacity of the initial
design of the morning glory spillway is limited to some 58m
3
/sec.
OPTIMISATION AND FINAL DESIGN
The initial design modication aimed at improving the ow condi-
tions in order to ensure safe operation, avoiding water column sepa-
ration at the throat of the transition tube. The modication should
also increase the discharge capacity to 75m
3
/sec. VAW developed a
modied design consisting of:
r An increase of the shaft diameter from 2-2.35m resulting in a
crest diameter of 8.35m, without altering the drop inlet location
and shape.
r A re-design of the bottom bend, including a throttle at its end,
to raise the pressure gradient ensuring pressures higher than the
140
120
40
20
0
Spectral density (mWC
2
/Hz)
Modified design Q - 65 m
3
/s
Final design with overflow piers, Q = 65 m
3
/s
Final design with overflow piers, Q = 75 m
3
/s
0 0.2 0.4 0.6 0.8 1.0
Frequency (Hz)
Modified design without overflow piers
Final design with overflow piers
Curve fit, free overflow conditions, C
d
= 0.459
Curve fit, full pipe flow conditions
540.5
539.5
538.5
537.5
H (m.a.s.l.)
540.5
539.5
538.5
537.5
H (m.a.s.l.)
538.97 m.a.s.l. maximum emergency water level
540.5 m.a.s.l. dam crest
537.5 m.a.s.l.
morning glory crest
020406080
Q (m
3
/s)
Vortex formation
in the overflow structure
Q = 72 m
3
/s
maximum discharge capacity
of the modified initial design
Q = 75 m
3
/s at 538.8 m.a.s.l.
for the final design
Q = 58 m
3
/s
maximum
discharge
capacity for
prototype conditions
537.5 m.a.s.l.
morning glory crest
538.97 m.a.s.l. maximum emergency water level
540.5 m.a.s.l. dam crest
Crest control
Full pipe flow
020406080
Q [m
3
/s]
Water column separation:
the hydraulic model
does not represent
prototype conditions
Q
Q
Chute spillway out of operation
(hypothetical scenario)
Chute spillway in operation
Curve fit, C
d
= 0.468
510.0
490.0
530.0
02040
(m)
60 80
538.73
H (m.a.s.l.)
0 20 40 60 80
3
3
–19.4 mWC
d
shaft
= 2.0m
En
erg
y gradient
Pres
sure gradient
Idea axis
493.5
∆H
geo
= 45.23m
Q = 72 m
3
/s
v = 22.9 m/s
entrance
v
2
/2g =26.8 mWC
k
s
= 0.6mm
= 0.015
= 0.05
= 0.15
bend
140
120
40
20
0
Spectral density (mWC
2
/Hz)
Modified design Q - 65 m
3
/s
Final design with overflow piers, Q = 65 m
3
/s
Final design with overflow piers, Q = 75 m
3
/s
0 0.2 0.4 0.6 0.8 1.0
Frequency (Hz)
Modified design without overflow piers
Final design with overflow piers
Curve fit, free overflow conditions, C
d
= 0.459
Curve fit, full pipe flow conditions
540.5
539.5
538.5
537.5
H (m.a.s.l.)
540.5
539.5
538.5
537.5
H (m.a.s.l.)
538.97 m.a.s.l. maximum emergency water level
540.5 m.a.s.l. dam crest
537.5 m.a.s.l.
morning glory crest
020406080
Q (m
3
/s)
Vortex formation
in the overflow structure
Q = 72 m
3
/s
maximum discharge capacity
of the modified initial design
Q = 75 m
3
/s at 538.8 m.a.s.l.
for the final design
Q = 58 m
3
/s
maximum
discharge
capacity for
prototype conditions
537.5 m.a.s.l.
morning glory crest
538.97 m.a.s.l. maximum emergency water level
540.5 m.a.s.l. dam crest
Crest control
Full pipe flow
020406080
Q [m
3
/s]
Water column separation:
the hydraulic model
does not represent
prototype conditions
Q
Q
Chute spillway out of operation
(hypothetical scenario)
Chute spillway in operation
Curve fit, C
d
= 0.468
510.0
490.0
530.0
02040
(m)
60 80
538.73
H (m.a.s.l.)
0
20
40
60
80
3
3
–19.4 mWC
d
shaft
= 2.0m
En
erg
y gradient
Pres
sure gradient
Idea axis
493.5
∆H
geo
= 45.23m
Q = 72 m
3
/s
v = 22.9 m/s
entrance
v
2
/2g =26.8 mWC
k
s
= 0.6mm
= 0.015
= 0.05
= 0.15
bend
140
120
40
20
0
Spectral density (mWC
2
/Hz)
Modified design Q - 65 m
3
/s
Final design with overflow piers, Q = 65 m
3
/s
Final design with overflow piers, Q = 75 m
3
/s
0 0.2 0.4 0.6 0.8 1.0
Frequency (Hz)
Modified design without overflow piers
Final design with overflow piers
Curve fit, free overflow conditions, C
d
= 0.459
Curve fit, full pipe flow conditions
540.5
539.5
538.5
537.5
H (m.a.s.l.)
540.5
539.5
538.5
537.5
H (m.a.s.l.)
538.97 m.a.s.l. maximum emergency water level
540.5 m.a.s.l. dam crest
537.5 m.a.s.l.
morning glory crest
020406080
Q (m
3
/s)
Vortex formation
in the overflow structure
Q = 72 m
3
/s
maximum discharge capacity
of the modified initial design
Q = 75 m
3
/s at 538.8 m.a.s.l.
for the final design
Q = 58 m
3
/s
maximum
discharge
capacity for
prototype conditions
537.5 m.a.s.l.
morning glory crest
538.97 m.a.s.l. maximum emergency water level
540.5 m.a.s.l. dam crest
Crest control
Full pipe flow
020406080
Q [m
3
/s]
Water column separation:
the hydraulic model
does not represent
prototype conditions
Q
Q
Chute spillway out of operation
(hypothetical scenario)
Chute spillway in operation
Curve fit, C
d
= 0.468
510.0
490.0
530.0
02040
(m)
60 80
538.73
H (m.a.s.l.)
0 20 40 60 80
3
3
–19.4 mWC
d
shaft
= 2.0m
En
erg
y gradient
Pres
sure gradient
Idea axis
493.5
∆H
geo
= 45.23m
Q = 72 m
3
/s
v = 22.9 m/s
entrance
v
2
/2g =26.8 mWC
k
s
= 0.6mm
= 0.015
= 0.05
= 0.15
bend
140
120
40
20
0
Spectral density (mWC
2
/Hz)
Modified design Q - 65 m
3
/s
Final design with overflow piers, Q = 65 m
3
/s
Final design with overflow piers, Q = 75 m
3
/s
0 0.2 0.4 0.6 0.8 1.0
Frequency (Hz)
Modified design without overflow piers
Final design with overflow piers
Curve fit, free overflow conditions, C
d
= 0.459
Curve fit, full pipe flow conditions
540.5
539.5
538.5
537.5
H (m.a.s.l.)
540.5
539.5
538.5
537.5
H (m.a.s.l.)
538.97 m.a.s.l. maximum emergency water level
540.5 m.a.s.l. dam crest
537.5 m.a.s.l.
morning glory crest
020406080
Q (m
3
/s)
Vortex formation
in the overflow structure
Q = 72 m
3
/s
maximum discharge capacity
of the modified initial design
Q = 75 m
3
/s at 538.8 m.a.s.l.
for the final design
Q = 58 m
3
/s
maximum
discharge
capacity for
prototype conditions
537.5 m.a.s.l.
morning glory crest
538.97 m.a.s.l. maximum emergency water level
540.5 m.a.s.l. dam crest
Crest control
Full pipe flow
020406080
Q [m
3
/s]
Water column separation:
the hydraulic model
does not represent
prototype conditions
Q
Q
Chute spillway out of operation
(hypothetical scenario)
Chute spillway in operation
Curve fit, C
d
= 0.468
510.0
490.0
530.0
02040
(m)
60 80
538.73
H (m.a.s.l.)
0 20 40 60 80
3
3
–19.4 mWC
d
shaft
= 2.0m
En
erg
y gradient
Pres
sure gradient
Idea axis
493.5
∆H
geo
= 45.23m
Q = 72 m
3
/s
v = 22.9 m/s
entrance
v
2
/2g =26.8 mWC
k
s
= 0.6mm
= 0.015
= 0.05
= 0.15
bend
Figure 5: Measured reservoir water level H as a function of the discharge Q in
the initial design of the morning glory spillway
Figure 6: Calculated energy and pressure gradient for Q=72m
3
/sec (initial
design of the morning glory spillway)
Figure 7: Top view of the reservoir with the modified design of the morning
glory spillway, with (1) service building, (2) protruding slope of the right
valley flank, (3) chute spillway and (4) dam. The surface flow field is high-
lighted using floating particles for a morning glory discharge of (a) 10m
3
/sec
(Q
chute
=0) and (b)72m
3
/sec (Q
chute
=187m
3
/sec)
Figure 8: Measured reservoir water level H as a function of the discharge Q in
the modified and the final design of the morning glory spillway
Fig. 9 (a) Top view and (b) detail of the final design of the morning glory spill-
way with overflow piers for a discharge of 75m
3
/sec with (1) service building
and (2) protruding right valley flank
Figure 10: Up-scaled spectral density at the pressure measuring position shown in
figure 11 for the modified design and the final design of the morning glory spillway
WWW.WATERPOWERMAGAZINE.COM OCTOBER 2010 33
SPILLWAYS
maximum tolerable negative pressure head of –(7 to 8)mWC at
the throat of the transition tube. According to common design
criteria, this is the minimum pressure head to avoid water
column separation.
r An increase of the spillway tunnel diameter to 2.35m.
r The addition of an air supply duct of at least 0.7m in diameter
behind the bottom bend to ensure sufcient air supply and free
surface ow in the spillway tunnel.
APPROACH FLOW CONDITIONS
The approach ow towards the morning glory is inuenced by the
protruding slope of the right valley ank and the service building
foundation nearby. However, for small discharges, all-around radial
ow occurs in the vicinity of the morning glory crest (see gure 7a).
At higher discharges the main ow towards the open chute spillway
circulates around the morning glory (gure 7b). Therefore, a strong
current develops in the region between the morning glory overow
structure and the right valley ank.
This ow is deected by the service building foundation, which
negatively inuences the velocity distribution in the vicinity of the
morning glory. For reservoir water levels higher than 538.9masl, a
bathtub vortex develops in the morning glory overow structure. A
considerable amount of kinetic energy is stored in the strong rota-
tional motion resulting in a reduction of the discharge capacity, ie
the discharge decreases for increasing reservoir water level (gure
8). With increasing reservoir water level, the vortex persists and the
discharge capacity is diminished.
The maximum discharge transported by the modified design
of the morning glory spillway reaches 72m
3
/sec at 538.9masl.
Consequently, the modied design did not reach the required dis-
charge capacity of 75m
3
/sec.
For the nal design, four overow piers (0.4m wide and 2m long)
are implemented on the modied design of the morning glory crest
ensuring radial inow conditions (see gures 4 and 9).
The design discharge of 75m
3
/sec is attained at a water level of
538.8masl. The ow condition has then just turned from free to sub-
merged at the morning glory overow structure. The overow piers
enforce radial inow and suppress the vortex formation enhancing
the hydraulic performance. However, the current along the right
valley ank towards the open chute spillway is still strongly deected
by the service building foundation. A three-dimensional ow eld
develops resulting in a single vortex-jet in the vicinity of the morn-
ing glory crest. This vortex may lead to erosion processes in the sur-
rounding area and debris entrainment.
For discharges higher than 75m
3
/sec and for reservoir levels above
538.8masl, the morning glory spillway operates under pressure. The
vertical shaft, however, already chokes for discharges superior to
56m3/sec. For the maximum emergency water level of 538.97masl, a
discharge of 76.7m
3
/sec was measured.
DYNAMIC PRESSURES
For discharges up to 40m
3
/sec the mean pressure heads, along
the cup-shaped overow structure and the vertical shaft, are
near the atmospheric pressure and the pressure uctuations are
rather small. For discharges higher than 56m
3
/sec, full pipe ow
conditions are observed and sub-atmospheric pressures occur in
the upper part of the vertical shaft. A minimum mean value of
–6.53mWC is detected at the throat of the transition tube for a
discharge of 75m
3
/sec (nal design with overow piers). This is
in accordance with the design criteria. Nevertheless, up-scaled
local sub-pressures drop below vapour pressure. These low pres-
sures lead to ow pulsations with considerable pressure peaks,
probably including the formation of localized cavitation bub-
bles. These phenomena may damage the concrete surface. As
a certain amount of air is entrained into the ow, the negative
consequences are minimised.
Prototype experience with similar structures shows no cavitation
damages if the mean pressure is above the vapour pressure. The
occurrence of extreme minimum pressures below vapour pressure
could be avoided by raising the pressure gradient in order to obtain
a higher mean pressure at the throat of the transition tube. This
may be achieved by vertical shaft enlargement and adequate throttle
orice adaptation.
Particular attention has to be paid to the pressure uctuations in
the vertical shaft due to the formation of an oscillating boil and two-
phase ow phenomena during the transition phase from free to full
pipe ow. These pressure uctuations are analysed by determining
the spectral density of a time series, ie the frequency of the measured
pressures. For a discharge of 65m
3
/sec the spectral density shows
one distinct peak at 0.03Hz (gure 10). This is the well-dened
oscillation frequency of the boil causing a pressure amplitude of
1.8mWC for the modied design and 0.7mWC for the nal design
with overow piers.
During submerged inow conditions, ie for Q≥ 75m
3
/sec, the
asymmetrical approach ow conditions towards the morning
glory spillway without overow piers, lead to the formation of
an air-core vortex within the overow structure. This phenom-
enon causes additional intensive pressure uctuations due to
unstable ow conditions as the air core bathtub vortex intermit-
tently collapses in the inlet structure (gure 11). Instantaneous
uctuations up to 20mWC are detected. The nal design with
overow piers avoids this bathtub vortex formation, reducing
the pressure uctuations. The spectral analysis shows no peaks,
ie no signicant pressure uctuations occur in the vertical shaft.
CONSTRUCTION WORKS AND OPERATION
The update of the total available spilling capacity of the Val Noci
reservoir is a part of a major maintenance plan which includes works
at the dam and all its auxiliary structures.
The construction works for the morning glory spillway started in
2008. The vertical shaft was carried out by raise boring after rock
mass concrete reinforcements at construction site. The over ow
structure’s internal prole was obtained using a prefabricated steel
formwork. To date, no signicant information about the morning
glory operation is available.
Mattia PINOTTI, Dipl. Bau-Ing. ETH, Hydraulic
Engineer at Lombardi Engineering Ltd., Minusio
(Switzerland), formerly: Laboratory of Hydraulics,
Hydrology and Glaciology (VAW) of ETH Zurich
(Switzerland), Email: mattia.pinotti@lombardi.ch
Adriano LAIS, Dipl. Bau-Ing. ETH, Head of the
Hydraulic Structures Division at Laboratory of
Hydraulics, Hydrology and Glaciology (VAW) of ETH
Zurich (Switzerland). Email: lais@vaw.baug.ethz.ch
IWP& DC
Figure 11: Side view of (1) vertical shaft, (2) bottom bend, (3) aeration duct
and (4) spillway tunnel of the morning glory spillway for (a) transition phase
at 65m
3
/sec, final design; (b) modified and (c) final design at submerged
inflow conditions. Without overflow piers air entrainment occurs batch-wise
causing strong pressure fluctuations
ENVIRONMENT
Submerged trees at Lois Lake, British Columbia
What lies
beneath?
Underwater trees in reservoirs can pose a multitude of problems worldwide. Removal
prior to ooding has never been as simple as it sounds, while harvesting afterwards has
long seemed like science-ction. However, Canadian company Triton Logging has gained
over ten years of experience in developing underwater forestry on a commercial scale.
WWW.WATERPOWERMAGAZINE.COM OCTOBER 2010 35
ENVIRONMENT
A
ROUND the world, an estimated 300M trees stand sub-
merged beneath the waters of dam reservoirs. Though
out of sight and out of mind for most people, these
trees represent both a challenge – and an opportunity
– for reservoir managers, local communities and governments.
Increasing attention on environmental, social and public safety
issues has prompted dam owners to seek innovative solutions and
partners to the problem of underwater trees.
DECADES IN THE MAKING
Largely preserved in an oxygen-deprived environment, submerged
trees continue to affect the reservoirs in which they stand. Increasingly,
these trees are being highlighted by governments, non-governmental
organisations (NGOs) and communities as something that cannot be
ignored. The incentives to address this challenge – and the risks of not
doing so – have never been greater than they are today.
Removing standing timber prior to ooding has never been as
simple as it sounds while harvesting post-ooding has long seemed
like science-ction. Nonetheless, Triton Logging of British Columbia,
Canada has been developing the technology and expertise to survey,
assess and remove submerged trees on a commercial scale for over a
decade. Reservoir managers around the world – from North America
to West Africa – have engaged Triton as a critical component of their
reservoir management plans to make hydro facilities safer, more ef-
cient and to create a new standard of environmental performance,
economic development and corporate social responsibility.
THE CHALLENGE
Generally, reservoir managers identify the challenge of submerged
trees in three categories: safety, environment, and dam performance.
Safety – Reservoirs located in populated areas act as important
transportation corridors, recreational venues and economic drivers.
Boat trafc – including ferries, pleasure craft or shing vessels – use
these waterways on a daily basis and run the risk of hitting submerged
or partially submerged trees. Fluctuating water levels increase these
risks for even experienced operators. Large, tree-lled reservoirs with
underdeveloped marine safety provisions claim hundreds of lives each
year. Government, hydro managers and non-governmental organisa-
tions see a clear need for the creation of veried, navigable channels
where trees have been removed.
Environment – Global demand for green power is putting energy
sources under a new environmental lens and hydro is no exception.
Increased scrutiny of standards and performance demand not only com-
pliance but innovation. In a report on environmental impacts of dams
for The World Bank, experts highlight lower water quality, increased
oating weeds, and heightened greenhouse gas release as the primary
impacts of ooded forests, along with negative secondary effects such
as water-related disease and poor aquatic habitat. Increasingly, NGOs,
governments and funding agencies seek clarity from reservoir owners on
how the impacts of submerged trees are being addressed post-ooding.
Careful inventorying and eventual removal of trees can be a critical
component of environmental management plans.
Dam performance – Understanding how submerged trees impact
generation performance demands a shift from reactive thinking to
proactive management. Woody debris, weeds and turbine corrosion
due to poor water quality can be linked to the existence of submerged
trees. Creating a comprehensive plan to remove some or all trees can
mitigate these and other performance-related issues before they esca-
late into costly, long-term problems.
On the other hand, if addressed proactively and as part of an inte-
grated management plan involving all stakeholders, the removal of
submerged trees can also present opportunities for reservoir owners:
Local economic development – The removal of submerged trees
can significantly contribute to communities’ economic capability.
Harvesting marketable, environmentally certied underwater wood
can build value-added local wood economies or supplement existing
land-based bre supplies. Removing hazardous trees can open develop-
ment and recreational possibilities and create new, cost-effective trans-
portation corridors. And, in some cases, removing or thinning specic
tree zones can improve shing and aquaculture opportunities.
Community engagement – Each hydro manager holds a mandate
to work closely with all stakeholders and none can be more challeng-
ing – or potentially rewarding – than the community which surrounds
the reservoir. A well-planned timber harvest programme can create
the basis for positive dialogue and future-oriented relationships and
can help parties move past adversarial paradigms.
UNDERWATER LOGGING DRIVES INNOVATION
Ten years ago, the founders of Triton Logging had a vision to recover
the millions of trees that had been ooded by dam reservoirs around
the world. By providing a new source of legal and eco-certied timber
– underwater trees that no longer sequestered carbon, nor acted as criti-
cal natural habitats – Triton sought to set a new standard for forestry.
Triton’s rst step was to develop harvesting technologies that
would overcome the key obstacles that other underwater logging sys-
tems had faced. Previous attempts using divers were limited by depth
and were often dangerous. Other ideas were either too expensive, too
inefcient or simply didn’t work. Triton’s approach matched marine
technology with logging industry know-how to create two unique
and complementary tools, the Sawsh and SHARC Harvesters.
THE SAWFISH UNDERWATER HARVESTER
Developed and manufactured by Triton, Sawsh is a remotely oper-
ated vehicle (ROV) with eight video cameras, sonar and GPS and is
powered by a 75hp electric motor and biodegradable hydraulic uids.
Each Sawsh comes equipped with a large grapple and 55-inch chain-
saw which, in the buoyant water environment, allow it to cut and
handle trees larger than any land-based mechanical harvester. Trees
are oated to the surface using one of the 50 inatable airbags carried
inside the machine and attached with a bolt mechanism.
Sawsh uses patented technologies to nd, cut and surface sub-
merged trees. These specications give the Sawsh signicant advan-
Below: Triton Logging’s remotely operated Sawfish underwater harvester uses
patented technologies to find, cut and surface submerged trees
Below: Triton’s SHARC Harvester has been developed to tackle difficult shal-
low water submerged forests
36 OCTOBER 2010 INTERNATIONAL WATER POWER & DAM CONSTRUCTION
ENVIRONMENT
tages. The rst is deepwater access, as it navigates precisely by a
remote pilot on a barge as deep as any reservoir in the world, says the
company. Secondly, the patented airbag system de-couples the cutting
and surfacing processes, enabling the Sawsh to perform multiple
cuts without returning to the surface. Thirdly, its remote operation
means workers are safely out of harm’s way. And, nally, with no
need to build roads, ght forest res and insects, or replant trees,
Triton’s underwater logging approach holds signicant cost advan-
tages and a reduced environmental footprint.
Triton has built Sawsh that have worked successfully across a
range of reservoir and forest environments from Canada to Malaysia.
Each tree cut has been marked with a GPS coordinate and can be
accessed for channel marking and other navigational purposes.
THE SHARC UNDERWATER HARVESTER
Following the success of Sawsh in deep-water reservoirs, Triton
developed its shallow-water tool in 2009. Soon to be deployed at
Volta Lake, Ghana, Triton’s patent-pending SHARC underwater
harvester brings new capabilities and exibility to the removal of
submerged timber.
Utilising a customised, fully-integrated barge and excavator, the
SHARC can precisely navigate using thrusters and a dynamic positioning
system (DPS). Capable of reaching up to 36.5m, the SHARC’s telescop-
ing boom and highly manoeuvrable cutting head can harvest quickly and
efciently using one operator. Side bunk log cradles hold the cut trees
and are towed to shore while the SHARC operator continues harvest-
ing. Remote cameras, sonar and GPS guide the operator and, as in the
Sawsh system, can provide precise coordinates of each tree cut.
Though focused initially on wood value, Triton always understood
that removing submerged trees had other critical benets for reser-
voirs. As the business developed the company engaged with the hydro
industry to better understand how Triton’s experience and tools could
support specic reservoir objectives.
Triton’s approach can be broken down into four key components:
rAssessment, which can involve pre-ood data collection, use of
satellite imagery and eld work to understand the problems and
develop potential solutions
rPlanning includes budget development, environmental permitting
and customisation of equipment and software
rTree removal takes advantage of its patented SHARC and Sawsh
Harvesters, as well as GPS and visual verication technologies
rMaintenance involves everything from post-project mapping to
data management and project integration and supervision
rUsing Triton’s multi-stage approach allows reservoir managers to
develop customised project solutions to match individual needs. In
this way, Triton’s project plan can account for scheduling restric-
tions – such as ood seasons and wildlife, environmental and indus-
trial activity – that offer project managers the exibility to meet
budgetary, community and business priorities.
CASE STUDIES SHOW RESULTS
Trilateral Partnership in Northern Canada
Ootsa Lake is part of the Nechako reservoir in northern British
Columbia, Canada and was built by Alcan (now Rio Tinto Alcan) to
generate power for its Kitimat aluminium smelter in the early 1950s.
More than 10Mm
3
of pine and spruce were ooded; however, all
previous salvage attempts had been unsuccessful.
In 2005, the company engaged Triton Logging in a pilot project
with a long-term goal in mind – salvage enough marketable bre
to sustain a modest-sized industry of 100 to 300 jobs for 50 to 75
years. Working under contract to Alcan and in collaboration with the
Cheslatta Carrier Nation, Triton deployed two Sawsh. A total mer-
chantable volume of 1093m
3
was harvested and 7.1ha of emergent
snags were cleared. The operation was certied by The Rainforest
Alliance’s SmartWood Rediscovered Wood programme and met or
exceeded all standards set by Alcan and regulatory agencies.
“Through this underwater logging initiative, the company is work-
ing with regional stakeholders and the government to develop an
associated industry and to bring value to local stakeholders,” reported
Alcan. “Facilitating access to the valuable submerged timber will also
help mitigate an expected downturn in the forest industry. By devel-
oping a deeper relationship with the community, Alcan has fostered
open dialogue and created a more collaborative environment.”
“The pilot project went well in the rst year and even better the
next,” says Triton’s Vice President of Operations, Richard Shipley.
“We continue to view Ootsa Lake and other BC reservoirs as great
places to show a shared approach to submerged forest management.”
Salmon enhancement project
More recently, Triton was asked to survey and plan the removal of
biomass in an area earmarked for a proposed salmon propagation
facility on a US hydro reservoir.
Triton deployed two different sonar surveys for the assessment
work. Multi-beam sonar was used to identify and target underwa-
ter obstacles, forested areas and anthropogenic structures within the
survey area. Sonar transects were conducted over the entire survey
area in both east/west and north/south directions with 50% transect
overlap to ensure 100% coverage and to determine anomalous
returns. The data was processed by Triton’s team to give spatial ref-
erence of any object and its depth information within the survey area,
allowing them to: locate areas requiring obstacle removal or further
sampling; identify the size of the proposed removal/sample areas;
approximate tree heights and water depths; and produce a bathy-
metric map in digital and paper format.
High resolution sonar was then used to detail tree and obstacle
characteristics, including stem and canopy proles and tree height
and diameter. Both surveys identied the presence of woody obsta-
cles in the form of standing and downed trees and stumps throughout
the survey area. “The client now has the results of our work and
our analysis of what it will take to remove the problem trees,” says
Shipley. “We expect to start the tree-removal phase this fall.”
THE FUTURE OF SUBMERGED FORESTS
Triton and its partners around the world continue to explore the
immense value of underwater logging. Increased social and environ-
mental expectations point to a growing need for dam owners and
managers to understand and address the challenges and opportunities
posed by submerged forests.
“We’ve had hydro managers approach us on a regular basis
because they need to meet new social and environmental criteria set by
funders,” concludes Shipley. “The World Bank, IFC and other inter-
national nancial institutions want to know what reservoir owners
and managers are going to do with ooded trees.”
Jim Hayhurst is Vice President, Marketing at Triton Logging
and manages the company’s Industrial Services Business.
He can be contacted at jim.hayhurst@tritonlogging.com
IWP& DC
Above: Triton wood harvested from Lake Kenyir, Malaysia brings value to
local communities
WWW.WATERPOWERMAGAZINE.COM OCTOBER 2010 37
ENVIRONMENT
T
HE 192MW Allain Duhangan hydropower project is a run-
of-river scheme that began commercial operation in April
2010. Located in the Kullu district of Himachal Pradesh in
northern India, it was built on the Allain and Duhangan
tributaries of the Beas river. The build-own-operate project is owned
by the Allain Duhangan Power Company Limited. Sponsorship was
given by the Indian rm Bhilwara Group, with support from SN
Power and the International Finance Corporation (IFC).
COMPLAINTS
Although the design of the Allain Duhangan project involved divert-
ing the majority of the Duhangan, project sponsors had made com-
mitments to ensure that sufficient water flows were left for the
downstream village of Jagatsuk. However, in October 2004, village
residents were unhappy and lodged a complaint with the Compliance
Advisor Ombudsman (CAO).
The CAO is an independent ofce within the World Bank Group
charged with responding to complaints raised by people who believe they
may be negatively affected by IFC-supported projects. It reports directly
to the president of the World Bank and seeks to assist parties in nding a
jointly agreed settlement to the complaint that has been raised.
The complainants believed that water supplies would dry up due
to the project’s diversion of the Duhangan river, with negative con-
sequences on agriculture and tourism. They also expressed concerns
about safety during construction, protection of religious sites affected
by water diversion, plus the adequacy of potable water. The complain-
ants also stated that the Environmental and Social Impact Assessment
(ESIA) documents prepared by the sponsor neither adequately consid-
ered the legitimate concerns of the villagers nor provided a sufcient
basis for informed consultation on key project impacts.
Upon initial assessment, CAO became concerned about the lack of
methodological rigour in the calculation of water ows and therefore
the manner in which ESIA requirements were managed. CAO also
noted that the ESIA document did not contain sufcient detail to allow
an informed decision on project environmental and social viability.
To make matters worse, the community also lacked a formal rep-
resentative body to express its concerns. The local government (the
Panchayat of Jagatsukh) dealt directly with the project company but
failed to communicate effectively with the local community. In turn
this led to misunderstandings in the village about the distribution of
project benets.
In response, CAO made ve site visits throughout 2005-7. It insti-
gated key stakeholder dialogue with complainants, the village govern-
ment, Bhilwara company ofcials and the district commissioner.
In 2006, as construction was underway, the CAO team was joined
by consultants from the Consensus Building Institute (CBI), a global
dispute resolution organisation. They were tasked with the role of
helping to design and facilitate conict resolution between commu-
nity stakeholders and the project owners. It also helped to bring local
language capacity and cultural knowledge to the team which was
critical in understandings village dynamics.
Over a period of two years CAO worked with the consultant team
to maintain contact with all stakeholders and keep up-to-date with
project activity. Improvements were also made to protect water sup-
plies; additional water studies were released; and safety and labour
conditions were addressed and enhanced. Furthermore the CAO
generated a Commitments Register for the hydropower project as a
means of tracking company performance against the ESIA.
In December 2006 the IFC visited the site to evaluate the situa-
tion and was satised with the company’s fullment of social and
environmental obligations. The case was closed in May 2007. After
a period of six months, based on the Commitments Register and peri-
odic supervision reports from the IFC, the CAO accepted that obliga-
tions had been met. By February 2008 the CAO had not received any
more complaints relating to project and so the case was concluded
one month later in March.
LESSONS TO LEARN
CAO believes that its involvement helped achieve a number of key
project-related outcomes, including better information sharing, great-
er company accountability, and on the ground improvement on key
social and environmental issues. It was able to provide a channel for
community grievances.
As the concluding documents about this CAO case stated, build-
ing relationships with groups that are on the boundary of project
impacts is essential. Although the sponsor and IFC believed that there
would no signicant impact on the Jagastsuk community due to the
EIA, some community members, such as farmers, saw little to gain
and much to lose from the project. There was much distrust of the
sponsor and local government and the community found it difcult
to believe that commitments would be upheld.
In hindsight it can be seen that detailed social mapping could have
uncovered key sectors of the community, and identied their percep-
tions of risks and opportunities. This could have resulted in solutions
being found much earlier along in the process.
Greater project transparency also played a key role in settling issues
at the Allain Duhangan project. CAO was keen to share all informa-
tion. It strategically chose to make all documents publicly available
and encouraged the hydro company and community to address spe-
cic concerns in a transparent manner. Greater transparency can help
reduce misunderstandings and false rumours about project activity
and benets, as well as improve relationships within the community
and between the company and community.
Greater project transparency can quash
community fears about the development of
hydro projects, as the Compliance Advisor
Ombudsmen discovered at the Allain
Duhangan project in India
Seeing is
believing
IWP& DC
Top: Project construction was underway at Allain Duhangan but village
opposition to the scheme had not been resolved; Above: Staff from the
Compliance Advisor Ombudsmen met with local farmers to address concerns
PROFESSIONAL DIRECTORY
38 OCTOBER 2010 INTERNATIONAL WATER POWER & DAM CONSTRUCTION
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