Johannesburg: Measures are being implemented by the Department of Water and Sanitation to release water from the Sterkfontein Dam into the Vaal Dam, aiming to augment its levels once it reaches 18% of its capacity. This strategy is part of the department’s standard operating procedure to manage water resources effectively.

According to South African Government News Agency, the Vaal Dam is currently at 28.2% and has been experiencing a weekly decrease of 1.5 to 2%, attributed to various climatic factors. These include low inflows due to insufficient rainfall in the Vaal catchment area and elevated temperatures leading to increased evaporation losses. The geographical features of the Vaal Dam, being wide and shallow, make it particularly vulnerable to such evaporation.

Additionally, the decrease in water levels is compounded by the closure of the Lesotho Highlands Water Project (LHWP) tunnel for planned maintenance. This tunnel is crucial as it transfers 780 million cubic metres of water annually into the Int
egrated Vaal River System (IVRS), but there was a shortfall of 80 million cubic metres this year due to the shutdown.

Despite the tunnel closure, an analysis by the department indicated that the overall performance of the IVRS would remain stable, as other dams within the system, including Sterkfontein, are sufficiently full. The maintenance, scheduled from 01 October 2024 to 31 March 2025, is not expected to disrupt water supply to Rand Water and its municipal customers across Gauteng and other provinces.

The department’s risk assessment in May 2024 suggested a 5% probability of needing releases from Sterkfontein Dam to support the Vaal Dam. This probability has now been realized due to ongoing below-normal rainfall and high evaporation rates. Consequently, a notice has been issued to water users and the public along the Nuwejaarspruit and Wilge Rivers about the potential release of water from Sterkfontein Dam. They have been advised to remove movable equipment, such as irrigation pumps, and avoid low-lyin
g bridges by 15 December 2024.

It is estimated that the water released from the Sterkfontein Dam will take approximately three to four days to reach the Vaal Dam, providing a crucial boost to its water levels.