dam is a double curvature arch dam 82 m high with a
storage capacity of 128,7 million m3. Provision
was made in the design to allow for a future raising
of the water 1ev by some 15,2 m. The construction of
the wall marked the beginning of an era of double curvature
arch dams in South Africa. Besides the normal central
overspill section, flood-control sluice gates with chute
spillways were provided on the left flank
dam has a catchment area of 388700 ha. The length of
the dam basin is approximately 34 km an the surface
area of the impoundment at full storage capacity is
555 ha. Geologically, the gorge within which the dam
is located, comprises strata of the Table Mountain sandstone
series in which layers of shale and tillite are included.
As the quality of the foundation material was not very
good, extensive measures for safeguarding the dam structure
and its foundations were required. These measures included:
construction of a series of tunnels in the right
flank, from which a system of drainage and grout
holes were drilled to prevent the development
of high uplift water pressures in the rock flank
construction of a thick reinforced concrete
slab against the right flank downstream of the
dam, and post-stressing thereof by means of
cables penetrating to a depth of 24 to 46 m
into the mountainside, to consolidate the rock
under the spiliway apron A comprehensive set
of observation instruments and observation points
in and on the dam wall was incorporated as part
of the normal monltoring procedure.
small hydroelectric power station with three turbines
of 1 200 kVA each was constructed on the right bank.
This makes use of the energy available from the water
discharged into the downstream canal. However, the generation
of power at this station is at present not economical.
Water is distributed to consumers by means of a system
of canals and pipelines. The main canal starts at the
dam and ends at the Loerie Balancing Dam. The canal
system consists of canals, siphons, balancing dams and
pipelines. The total length of the main canal is 97
km (72 km canal, 17 km siphons and 8 km tunnels). The
total length of the branch canals is 30 km and the total
length of the pipelines is 91 km. in addition to the
Loerie Balancing Dam, a further two balancing dams were
constructed along the route of the main canal to prevent
the wasting of water due to fluctuations of demand.
The main canal has a carrying capacity of 8,5 m3/s at
the Kouga Dam. The carrying capacity decreases
at each of the balancing dams until the ultimate caring
capacity at the point of discharge of the canal into
the loerie Dam is 3,1 m3/s.
Loerie Dam with a capacity of 3,4 million m3 consists
of an earthfill embankment with a clay core and a side
channel spillway on the left flank of the dam wall.
The dam also has a crest spillway which was added in
1983 after the earth embankment had been overtopped
on two occasions.
Kouga Dam and the main canal supply water for both
irrigation and urban use; the branch canals are used
mainly for irrigation and the Loerie Dam for urban water
supply only. Water is supplied to the Port Elizabeth
Municipality's purification works at the Loerie Dam
site by means of an outlet control tower and tunnel.
the Kouga Dam, irrigation water is supplied by
means of the canal and pipeline system to 7400 ha of
scheduled ground. Every irrigator is supplied with at
least one draw-off with a selfregistertng meter, which
he himself can operate according to his needs, up to
a mamum Iimit of 8000 m3 per ha per year.
Kouga Dam was also built to serve as a flood-control
dam for floods originating from the catchment area of
the Kouga Rtver and to decrease the effects of these
floods in the lower Gamtoos area.
Valley downstream of the dam, consists of alluvial deposits
of the Ultenhage Series composed of round pebbles, shales
and clays, forming near-vertical cliffs of conglomerate.
Typical vegetation up against the slopes consists of
succulents such as elephant's food, candelabra trees
and aloes forming dense, Impenetrable thickets. Dense
thorn-trees, yellow wood, wild olive, sneeze-wood, wild
fig and many other trees and tall bush grow on the plains
and along the beds of the tributaries.