The River
The Ruacana Falls is situated in the Kunene river in northern
Namibia. After a southbound run, the river makes a right turn to
flow directly to the Atlantic, creating a natural setting for the
Ruacana hydroelectric scheme. From here, on the bank of the Kunene
River, Namibia draws most of it's life-sustaining power. To
accommodate the three 80 megawatt turbine generators, as well as
transformers, the switchgear, and the entry and discharge tunnels,
more than 400 thousand cubic meters of rock had to be removed. Water
from the Kunene River is regulated by a series of dams and a
diversion weir, to channel part of the flow to a surge head bay on
top of the mountain.
The Powerstation
The water drops almost 134m down vertical shafts into the heart of
the mountain, where it drives the turbines before rejoining the
Kunene from a discharge tunnel. When in full operation, the three
turbines can generate about 240 Megawatts, which is fed into the
Namibia Power Grid at 330 000 volts. Today the Ruacana hydroelectric
power station is still the core of Namibia's power supply system.
The first component of the Ruacana hydraulic system is the Diversion
Weir, situated in Angolan territory. The Weir consists of a
concrete gravity overspill structure with flap gates to control
flood regulation, also incorporating the pressure tunnel intake.
From the Diversion Weir a 1 500m long Pressure Tunnel runs along the
southern bank of the river, some 30m below the ground.
After crossing the border the Pressure Tunnel
continues through a fault zone in the Palmwash ravine, then pours
into an oval shaped Surge Headbay, 31.5m in depth. The Surge Headbay
is connected to an underground powerhouse complex consisting of
three large parallel caverns, draft tubes and interconnecting
galleries and ducts. The larger cavern houses the machine hall,
turbines, a control building and the workshop area. Next to the
cavern is the 120m long Transformer Hall, just above the horizontal
section of the Penstocks. A third chamber on the southern side if
the machine forms the Surge chamber, 70m long and 28m high. From
here a 675m long Tailrace Tunnel discharges water to the river in
correspondence with the Hippo Pool. The Access Gallery of 300m
connects the caverns with the outside. On the surface next to the
Surge Headbay, a switchgear lift and diesel building is located.
Geology
The large blocks of porphyroblastic gneiss, pink to grey in colour,
characterise the geology at Ruacana, with incidental intercalation
of chlorite-schists, hornblende schists and mica-schists materials.
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