Vaal Dam

The Vaal Dam in South Africa was constructed in 1938 and lies 77 km south of OR Tambo International Airport. The lake behind the dam wall has a surface area of about and is 47 meters deep. The Vaal Dam lies on the Vaal River, which is one of South Africa's strongest-flowing rivers. Other rivers flowing into the dam are the Wilge River, Klip River, Molspruit and Grootspruit. It has over of shoreline and is South Africa's second biggest dam by area and the fourth largest by volume.HistoryThe construction of Vaal Dam started during the depression of the early thirties and the dam was completed in 1938 with a wall height of above lowest foundation and a full supply capacity of. The dam is a concrete gravity structure with an earthfill section on the right flank. It was built as a joint venture by Rand Water and the Department of Irrigation (now known as the Department of Water Affairs).The dam was subsequently raised in the early fifties to a height of which increased the capacity to. A second raising took place in 1985 when the wall was raised by a further to above lowest foundation. The capacity of the dam is currently and a further or 26% can be stored temporarily for flood attenuation.The flood attenuation properties of the dam were severely tested in February 1996 when the largest flood ever recorded at the Vaal Dam site was experienced. An inflow of over was measured into the Vaal Dam which was already at full capacity due to good rains and it was only through the expert management of the Hydrology staff at DWAF that the maximum flood released from the dam was limited to. Flows above would have caused serious damage downstream of Vaal Dam and the situation during the 1996 flood became extremely tense as the storage in the reservoir peaked at 118.5% of Full Supply Capacity on 19 February 1996 i.e. only of flood absorption capacity remained before the full inflow would have been released causing massive damage.