Meaning of a dam
A dam is a barrier constructed to hold back water and raise its level,
forming a reservoir used to generate or as a water supply
IMPORTANCE OF DAMS
1) Dams are
important because they provide water for domestic, and irrigation purposes
2) Dams often
also provide hydroelectric power production and river navigation
3) Dams and
their reservoirs provide recreation areas for fishing and boating.
4) They help
people by reducing or preventing floods
USES OF DAMS
A dam is constructed mainly for power
generation, irrigation/water supply or flood prevention. However in most of
cases dams have multiple functions. The main uses of a dam are presented below
hydroelectric power is a major source of electricity and the world.
Reservoirs created by dams not only
suppress floods but also provide water
for activities such
as irrigation, human consumption, industrial use, aquaculture and navigability
hydropower is often used in conjunction with dams to generate electricity .
ADVANTAGES
OF DAMS
1) Once a dam is constructed, electricity
can be produced at a constant rate
2) If electricity is not needed, the
sluice gates can be shut, stopping electricity generation. The water can be saved for use another time when
electricity demands is high
3) Dams are
designs to last many decades and so can contribute to the generation of
electricity for many years/decades
4) The lake’s water can be used for
irrigation purposes
When in use, electricity produced by dam
system does not produce green house gases. They do not pollute the atmosphere.
DISADVANTAGES
OF DAM
1) Dams are extremely expensive to build
and must be built to a very high standard.
2) The high cost of dams’ construction
means that they must operate for many decades to become profitable.
3) The flooding of large areas of land
means that the natural environment is destroyed.
4) People living in villages and towns
that are an the valley to be flooded, must move out
5) The bunding of large dams can cause serious geological
damage
TYPES OF
DAMS
1) Arch dam
2) Buttress dam
3) Coffer dam
4) Diversion dam
5) Embankment dam
6) Gravity dam
7) Hydropower
dam
8) Industrial
dam
9) Masonry dam
10)
Overflow dam
11)
Regulating (After bay) dam
12)
Saddle or dike dam
HOW TO BUILD A DAM
Construction of a dam__ STEP I to build a dam the engineers
must first de water the part of the river valley an which they wish to place
the dam. This is usually achieved by diverting the river through one side of
the valley around the planned construction area a series of holes is denied in
the rock explosive are placed in drill holes, blasting takes place and broken
rock is then removed. This procedure is repeated many times until the tunnel is
computed diversion tunnels are often lined with concrete.
STEP 2
Work on diverting the river starts
in summer when river levels are low earth moving equipment is used to build a
small dam (called a coffer dam) upstream of the main construction area. This
act as a barrier to the river and cause it flow through the diversion tunnel.
Another coffer dam is built
downstream of the main dam site to prevent water flowing back into the
construction area. Pumps are used to remove water that step to the cofferdam.
Diversion tunnel are not always necessary when concrete dams are being built.
The river can sometimes be channeled through a large pipe and the dam
constructed round it
STEP 3
The construction method used in building a dam
depends on the type of dam being built. The first stage normally involve he
removal to lose rock and rubble from the valley wall and river bed. Concrete
facing rock field dam require a footing (or punt) to be constructed around
their off-stream edge. The plinth is made from concrete and serves as a
foundation or connection between the dam and the valley walls and floor. It has an important role in preventing water
leaking around the edge of the dam. The area under the punt is waterproofed by
drilling holes and pumping cement grout into cracks in the rock. The thin
concrete face on the upstream side of the dam is connected to the plinth via
stainless steel and rubber seal called water stops
STEP 4
During dam construction the
associated power station and intake works are also being built when the dam is
completed the diversion tunnel is closed and the lakes begin to flow to fill.
The closure of the diversion tunnel has two
phases. During low flow a large reusable steel gate is lowered across the
entrance. The diversion tunnel is then permanently blocked off by the
construction of a concrete plug. In some
instances, dewatering outlets are built into the plugs so water can be released
during an emergency.
LISTS OF DAMS AND RESERVOIRS IN NIGERIA
1. Ede-erinle
reservoirs found in Osun State
2. Asejire
reservoirs found in Oyo State
3. Bakolori
dam found in Sokoto State
4. Challawa
gorge dam found in Kano State
5. Dadin kona
dam found in Gombe State
6. Goronyo dam
found in Sokoto State
7. Ikere gorge
dam found in Oyo State
8. Jebba dam
found Niger State
9. Jibiya dam found in Kastina State
10.
Kafin zaki dam found in Bauchi State
11.
Kainji dam found in Niger state
12.
Kiri dam found in Adamawa state
13.
Oyan river dam found in Ogun state
14.
Shiroro dam found in Niger state
15.
Tiga dam found
in Kano State
16.
Zauro polder project found in Kebbi State
17.
Zobe dam found in Kastina State.
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