Kogelberg Dam and Palmiet Pumped Storage Scheme, Western Cape

This photograph captures the downstream face of Kogelberg Dam on the Palmiet River in the Western Cape, showing the concrete dam wall set within the steep, fynbos-covered landscape of the Hottentots Holland Mountains. The image provides a clear view of the substantial dam structure from the downstream river valley, with the Palmiet River flowing away from the dam through a naturally vegetated channel. The contrast between the engineered concrete wall and the rugged surrounding landscape illustrates the distinctive character of the Palmiet Pumped Storage Scheme, one of South Africa’s important hydroelectric and water-transfer infrastructure projects.

Kogelberg Dam is located on the Palmiet River south of Grabouw and forms the lower reservoir of the 400 MW Palmiet Pumped Storage Scheme. The scheme consists of Kogelberg Dam as the lower reservoir, Rockview Dam as the upper reservoir and an underground pumped-storage power station situated between them. Eskom operates the electricity-generating component of the scheme, which consists of two 200 MW reversible pump-turbine units and was fully commissioned in 1988.

The dam is considerably more than a conventional water-storage reservoir. It forms part of a dual-purpose infrastructure system combining electricity generation and water transfer. During periods of low electricity demand, water can be pumped from Kogelberg Dam to the much higher Rockview Dam. When electricity demand rises, the stored water is released from Rockview through the underground waterways and reversible turbines, generating electricity before returning to Kogelberg Dam. Eskom states that the Palmiet station can respond to changes in electricity demand extremely rapidly and supply power to the grid within approximately two and a half minutes.

The photograph is particularly interesting because it shows the downstream side of the lower reservoir rather than the large expanse of water normally associated with a dam. The concrete wall is positioned between two steep natural ridges, with the downstream Palmiet River continuing through the valley below. The structure appears relatively compact when viewed from this perspective, but its technical specifications reveal its substantial scale.

According to Eskom’s technical information, Kogelberg Dam is a mass concrete gravity arch wall with a separate earth saddle embankment. The concrete wall contains approximately 70,000 cubic metres of concrete, while the associated earth embankment contains approximately 220,000 cubic metres of material. The concrete section has a maximum height of 57 metres above the river bed and a crest length of approximately 186 metres.

The dam has a gross storage capacity of approximately 19.3 million cubic metres, with an active storage capacity of about 15 million cubic metres. At full supply level, the reservoir has a surface area of approximately 155.4 hectares. Its spillway has a design capacity of approximately 1,060 cubic metres per second and uses an ogee-type arrangement.

The concrete structure visible in the photograph is therefore only one part of a much larger hydraulic system. Water entering Kogelberg Dam can ultimately be transferred through the pumped-storage system towards Rockview Dam, which is located at a substantially higher elevation on the watershed between the Palmiet and Steenbras river systems. The difference in elevation provides the hydraulic head required for the generation of electricity.

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