Adeleke, O.A.

Fadayomi, N.O.

English

Aquatic Commons

ENGINEERING INITIATIVES FOR WATER HYACINTH
CONTROL WITH EMPHASIS ON THE DESIGN,
CONSTRUCTION AND INSTALLATION OF WATER
HYACINTH BOOM (BARRIER) ACROSS RIVER NIGER,
NORTH OF KAINJI LAKE
N. 0. FADAYOMI and 0. A. ADELEKE
Nigerian Submarine Divers Ltd.
68 Jubril Martins Street, Surulere, Lagos, Nigeria
ABSTRACT
The paper describes the concept, design, component and field layout of a physical barrier
to control water hyacinth on Lake Kainji. in spite of the successes of a combination of
control methods evolved by the National Institute for Freshwater Fisheries Research
(NIFFR), New Bussa with the support of the on-going Nigerian-German Kainji Lake
Fisheries Promotion Project (N-G KLFPP) in clearing water hyacinth, yet the weed
continued to arrive annually. Thus, construction of a barrier was conceived as the means
to prevent the ingression. Towards this, the.N-G KLFPP invited and discussed with the
consultants to submit suitable proposals and design. The FISESCO-TALON JOINT
VENTURE produced the finally acceptable designs in 1999. The designs were vetted
and certified by the LAHMEYER INTERNATIONAL (Consulting Engineers for Energy,
Water, Environment and Transportation), Germany, appointed by the GTZ Headquarters.
The barrier comprising of two sections, rigid and floating, was funded by GTZ with the
Federal Government of Nigeria providing the counterpart funds to ensure maintenance,
provide break-up facilities for rbmoval and safe disposal of water hyacinth retained by
the barrier. The technology is recommended for use in other water bodies with similar
hydrological regimes
INTRODUCTION
The involvement of a sister Company
(FISESCO LIMITED) a group of which I
am the Chief Executive, in the control of
water hyacinth started around 1987 when
the weeds drifting from Benin Republic —
entered the Lagos lagoon system en-route
the eastern part of the coastal inland
waterways via Lekki Lagoon down to
Ondo State riverine areas. Further spread
of the weeds afterwards to other
freshwater systems within Nigeria is now
history.
31
Concerned by the deleterious effect of
this menace on inland fisheries and water
transportation, the then Ministry of
Science and Technology constituted' a
Committee of experts to find ways of
utilizing them.
While serious intellectual consulta-
tions were made as to the ways the weeds
could be utilized, the urgent need to
prevent the collapse of artisanal fisheries,
which the phenomenon threatened,
engaged the attention of the experts.
What's more, the hindrance that the carpet
of water hyacinth posed to transportation
of light crafts had started to stiffle the
economic activities of the riverine
communities on its path.
Whilst scientists worked on the
possibility of biological control, in
particular, the Committee agreed that
harvesting the weeds manually or
mechanically was the most practical
approach to bringing relief to the affected
communities. It was at this point that
FISESCO LIMITED a company
offering services in the development of
fisheries infrastructure and hardware
was invited to propose a contrivance that
could be deployed immediately to remove
the weeds and free the waterway from
Lagos-east to Lekki Lagoon. A ciane—
barge equipped with a drag-line to which a
grab-bucket was attached was contrived
and deployed for use for a period of ten
months. A lot of experience on
mechanical harvesting of water hyacinth
was gained thereby.
Experience showed that any
mechanical harvester of any manufacture
could not be very effective if deployed to
grope for clusters of water hyacinth which
formed as soon as the harvester dislodged
the carpet, thus causing the weeds to drift
in several directions. A proverbial "wild
goose chase" ensued as the clusters drifted
unpredictably, resulting in seemingly
uneconomic daily harvests. That is, the
time it took to fill a haul barge for disposal
was too long to optimize the use of the
mechanical option. During this time,
manual clearance was made supplemental
to the mechanical harvesting method.
It was during this exercise that
FISESCO LIMITED experimented on
creating a collection point, using
interlaced bamboo as barrier across water
at selected areas. It was interesting to note
that what took the harvester eight (8)
hours to remove was accomplished in one
(1) hour. Thus, it was found that any
mechanical harvesting device that might
be introduced for this service mUst have a
barrier or a boom as a complement to
optimize the efforts and the investments in
the control and evacuation of water
hyacinth from waterways.
Noticing the effectiveness and
complementarity of the barrier system to
the harvester, the National Electric Power
Authority commissioned NIGERIAN
SUBMARINE DIVERS LIMITED (a
sister company to FISESCO LIMITED) to
install a well engineered barrier at the
water intake area of Sapele Thermal
Power Station to aggregate the water
hyacinth which continuously got sucked-
up with water into their turbines, thus
creating the need fOr very expensive and
frequent descaling or flushing of the
generating plant. A barrier, well-suited to
that application was designed, constructed
and installed during 1990. This
innovation has aided effective harvesting
of water hyacinth from the entrance of the
water intake canal of the power plant.
THE RIVER-NIGER EXPERIENCE
CONCEPTUAL FRAM EWORK
The concept of aggregation of water
hyacinth for easy evacuation appealed to
GTZ — a German Donor Agency that had
invested a lot of aid
— money into fisheries
promotion within and around the Kainji
Lake area. The menace of water hyacinth
remained the major hurdle to the
actualization of its objective of empow-
ering the communities along the river-
valley through unhindered water transport-
ation of tradable products and unhindered
fishing operations on the River Niger and
within the Kainji Lake area.
Because of the difference in water
behaviour and wind flow pattern at the
32
chosen site — Zamare in Kebbi State
across to Rofia in Niger State — a different
barrier design became imperative. Taking
into consideration all the variables, an
anchor-buoy arrangement — which is used
for mooring commercial fishing vessels
mid-stream — was adopted to be replicated
and installed in series such that a boom or
barrier would be formed across the river
valley to aggregate the water hyacinth that
drift down the river towards Kainji Lake.
Because of variations in water levels
which occasion the flooding of the
landmass contiguous to the river valley, a
steel-mesh design frame was to be
adopted. This component which we refer
to as the rigid boom and the anchor-buoy
arrangement which we refer to as the
flexible boom, together constitute the
water hyacinth barrier or boom now in
operation since May 1999.
This GTZ financed Zamare/Rofia
Water Hyacinth Barrier Fojeet which was
vetted by LAHMEYER INTER
NATIONAL — a German corisultancy firm
— was designed, constructed, installed and
being maintained by NIGERIAN
SUBMARINE DIVERS LIMITED -
LAGOS (FISESCO LIMITED's sister
Company) under the supervision of
NIFFR.
DESIGN CRITERIA OF THE
ZAMAREIROFIA WATER
HYACINTH BARRIER
In our design of water hyacinth boom,
a lot of factors were considered with a
view to achieving a product that is
efficient, cost effective and serviceable.
These are:
effectiveness in trapping the weed
• local availability of material (to
reduce cost)
• technical/fabrication knowhow
durability of component parts
• ease of maintenance
• resistance to corrosion
• ability of the floating parts to keep
afloat
ability to adjust to varying water
levels
to withstand impact load
from wind, water, weed and
• ability to adjust to wave movement
(i.e. flexibility)
• ability to withstand extreme weather
conditions.
DETERMINATION OF FORCES
It is very important to determine the
forces expected on the boom in order to
adequately design its strength and size.
The basic forces considered in our design
are those due to water, wind, wave, weeds
and other debris.
In arriving at these forces, some
natural design parameters were physically
obtained or determined at the proposed
site of the boom. These are
Velocity of Flow of the River:
This was taken at various times during
the two seasons experienced in the area
i.e. flood and dry seasons. The flooding is
between September and February while
dry period is between March and August.
1. Density of Water:
This is the mass per unit volume of
water. It usually varies from slightly
saline to fresh water. Water samples were
taken at different times and density
• ability
arising
wave.
, 3
determined in each case. An average of
the measurements was then used for the
design.
2. Wind Speed:
Speed of wind in the locality was also
measured and recorded during the two
season. The maximum wind speed value
known as the peak value was adopted for
the design.
4. Wave Amplitude:
In inland waters, wave amplitude is
mostly dependent on wind speed. Efforts
were made to measure wave heights
during the periods of high wind speed.
5. Variathn in Water Level:
There is need to know the maximum
and minimum water levels including the
spread i.e. maximum and minimum width
of the river during high and low waters.
This enabled us to determine the tidal
heights and width of the flood plain. This
became very necessary because of the
need to determine the overall length or
coverage of the boom, and to know which
length of the barrier will be permanently
in water and that which will be in partial
contact with water i.e. having water during
the high water period and dry thereafter.
ESSENTIAL COMPONENTS OF THE
BOOM ASSEMBLY
The water hyacinth boom designed
and constructed by Nigerian Sub-marine
Divers Limited is in two sections. The
first section is the rigid barrier while the
second is the flexible boom. Due to
seasonal flooding on the Kainji Lake, the
rigid section is installed on the flood plain,
which receives water only between Sept-
ember and February while the flexible part
is installed to cover the actual river
channel which receives water all the year
round.
RIGID BARRIER (APPENDIX 5)
The rigid barrier consists of steel
support piles and sfeel screen.
Support piles
This is made up of steel casings 8
inches diameter driven at 3 metres interval
such that the depth of penetration is twice
the freeboard (i.e. depth beneath the
ground is twice the length above the
ground.). The interior of the casing was
reinforced with steel rods and filled with
concrete for additional strength after
which the external portion above the
ground was coated with epoxy resin to
avoid corrosion,
Steel Screen
The steel screen is made of flat
steel bars spaced at 100mm centre to
centre. Fabricated in units of 3 metres
wide and heights ranging from 1 metre
to 3 metres. Each 3 metres length is
placed to cover the gap between two
support piles and secured firmly by
welding on to the pile casing. The screen
was also protected against corrosion by
applying coats of epoxy resin.
FLEXIBLE BOOM
The flexible boom is the floating part.
It has the following members
(a) Steel buoys
(b) Anchor bollard with floating hook
(c) Pile anchors
(d) Warning signal buoys
Steel buoy (APPENDICES 2,3 & 4)
The steel buoys are designed and
fabricated in units of 1 .5 metre long x 1.2
34
metre width and 0.8 metre high. It is
made from flat steci sheet and reinforced
with steel angles.
Each unit is fitted with 2 No.. rubber
fenders to prevent buoy to buoy contact
which can damage the units. Attached
also are eight steel hooks, each of which is
capable of resisting 2 KN force and a
reflective sticker to define the boom
alignment at night.
The unit buoys are linked together by
high tensile chain fitted at the ends with
bolted shackles. A vent is provided at the
top of the buoy to ease internal pressure
build-up, which may result from hot
weather condition.
Anchor bollard with floating hook
(APPENDIX 6)
There are 2 No. bollards situated at
the banks of the river channel, to
anchor the flexible boom assembly at
one end. Each is designed for a
horizontal pulls of 90 KN force,
capable of holding up to 500 metre
length of boom.
The hook on the bollard is also
designed for same load (90 KN) with 2
No. floaters attached on the sides to allow
for variation in water levels.
Pile anchor (APPENDIX 4)
The pile anchors are submerged in
water. They are meant to anchor the
flexible boom assembly firmly to prevent
drifting and allow for proper alignment.
Each of the pile anchor is designed to
resist a minimum vertical pull of 9 KN.
Link between the buoy assembly and a
pile anchor is done with the use of
galvanized sling wire rope fitted with
shackles, bolts and nuts at both ends.
35
Warning signal buoys (APPENDIX 7)
Floating warning signals are incorpo-
rated into the design to warn the waterway
users of an impending obstacle to free
flow of traffic. The signal buoys are two
sets located one kilometer from the boom
up and downstream. Each set consists of
three signal buoys, two of which are
situated on each bank (left and right) and
the last one at the midstream.
Inscriptions on the ones at the bank
are in the native language (Hausa) while
the one at the midstream is in English
Language. Each of the buoys is held in
position by 3 No. 350kg concrete anchors
placed at the bottom of the river.
BOOM LOCATION AND LAYOUT
(APPENDIX 1)
The water hyacinth boom in question is
located upstream of Kainji Lake across
River Niger at Zamare in Kebbi State and
Rofia in Niger State. Zamare is accessible
from Kontagora — Sokoto Road while
Rofia is the last village on New Bussa
Agwara — Rofia Road. The barrier is
aligned at 60° to the river bank on both
sides. A five (5) metres wide passage is
provided along the rigid barrier to cater
for movement of animals and persons
during the low water period and canoes
that cannot get to the midstream because
of wind during high water.
At the midstream, there is a passage-
way wide enough (80 — 100 metres) for
ferries and passenger boats navigating up
and downstream. The configuration is
such that the Zamare wing of the boom
overlaps the other from Rofia thus
preventing weeds from drifting across.
CONCLUSION
Since the installation of the barrier in
May 1999, the influx of water hyacinth
weed into Kainji Lake has reduced
drastically. Quite a large volume of the
weeds which otherwise would have drifted
down the river are being trapped or
deterred by the facility at the point of
installation, thus making evacuation of the
weeds relatively easy for those engaged
for this service.
Inforniation reaching us from
villages down-stream of the barrier site
at Zamare/Rofia indicate tremendous
improvement in fisherfolk's ability to
operate unhindered by the weeds and
the freedom to navigate without any
obstacles up to the site of the boom
assembly.
Although the aggregation of water
hyacinth for harvesting was the object of
this initiative, experience at Zamare/Rofia
has shown that the barrier — as designed
and constructed — effectively aggregates
other floating weeds such as Niger grass
and other weed species, submerged plants
and logs.
It is to be recommended that where a
mechanical harvesting device is contem-
plated, an aggregating device (a boom or
barrier) should be made complementary
for optimal control of and evacuation of
water hyacinth, in particular from
waterways that may be so infested.
36
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Engineering initiatives for water hyacinth control with emphasis on the design, control and installation of the water hyacinth boom (barrier) across River Niger, north of Kainji Lake

http://aquaticcommons.org/968/1/WH_031-043.pdf

Engineering initiatives for water hyacinth control with emphasis on the design, control and installation of the water hyacinth boom (barrier) across River Niger, north of Kainji Lake

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