Vaal River System maintains strong water storage levels amid weekly fluctuations
The Department of Water and Sanitation (DWS) continues to monitor the major dams that form part of the Integrated Vaal River System (IVRS), with the latest assessment indicating that the system remains in a favourable water-storage position despite week-on-week fluctuations in individual reservoir levels.
The overall IVRS storage level has decreased from 97.7% last week to 96.7% this week. Although this represents a marginal decline, the system continues to retain substantial water reserves. Weekly changes in dam levels are influenced by several factors, including rainfall, catchment runoff, inflows from upstream areas, water consumption, evaporation, inter-basin transfers and controlled releases. The movement of an individual dam's storage level should therefore be viewed within the context of the broader interconnected system and does not, on its own, indicate a deterioration in the overall water-security position.
The Vaal Dam has recorded a slight decline from 100.0% last week to 99.7% this week. Despite the marginal decrease, the dam remains virtually at its full supply level and continues to hold a substantial volume of water. The change reflects normal fluctuations associated with inflows, water consumption, evaporation and operational releases. Given the strategic importance of the Vaal Dam to the water supply system, DWS continues to closely monitor its storage levels and operational conditions.
Grootdraai Dam has increased from 97.5% last week to 98.4% this week. The improvement brings the dam closer to its full supply level and reinforces its strong storage position within the IVRS. At 98.4%, the dam continues to provide a substantial reserve that contributes to the overall resilience of the system.
Bloemhof Dam has declined from 110.0% last week to 108.2% this week. Despite the decrease, the dam remains significantly above its defined full supply level and continues to hold substantial water reserves. A storage reading above 100% indicates that the reservoir water level is above the reference full supply level used for operational purposes. The current level therefore continues to reflect a strong storage position.
Sterkfontein Dam has recorded a marginal increase from 98.7% last week to 98.8% this week. The dam remains close to its full supply level and continues to maintain a strong storage position. Its near-full storage level provides an important reserve within the broader IVRS and contributes to the reliability of water resources available to the system.
Mohale Dam recorded a decrease from 101.7% last week to 94.1% this week. This is the most notable week-on-week change among the reservoirs monitored during the current reporting period. Despite the decline, the dam remains at a substantial storage level. The change should be understood within the operational management of the interconnected water-resource system, including transfers, releases, inflows and water requirements. Mohale Dam forms part of the Lesotho Highlands Water Project (LHWP), which plays an important role in augmenting water supplies to the Vaal River System.
Katse Dam has decreased from 80.1% last week to 79.0% this week. While the dam recorded a marginal decline, it continues to retain a significant volume of water and remains an important component of the LHWP and the broader water-supply system. DWS continues to monitor storage levels at Katse and Mohale dams as part of the ongoing management of water transfers into the IVRS.
The Integrated Vaal River System currently stands at 96.7%, compared to 97.7% during the previous reporting period. Despite the one percentage-point decrease, the system remains close to full supply and continues to hold substantial water reserves. The IVRS is a strategically important network of dams and water-resource infrastructure that supports water supply to Gauteng and surrounding areas. The system plays a critical role in meeting the water requirements of households, industries, agriculture and other socio-economic activities.
As an interconnected system, its overall water-storage position is influenced not only by individual dam levels, but also by inflows, transfers, controlled releases, rainfall, evaporation and water demand. Consequently, short-term fluctuations in individual reservoirs are a normal feature of the operational management of the system.
While the current storage position of the IVRS remains favourable, DWS urges all water users to continue using water responsibly and to avoid unnecessary wastage.
Maintaining high storage levels does not remove the need for water conservation. Responsible water use is essential to preserve available resources, particularly in the context of increasing water demand, population growth, infrastructure pressures and changing rainfall patterns associated with climate variability and climate change.
The Department will continue to closely monitor dam levels, catchment conditions, inflows, transfers, releases and water-use patterns across the IVRS. DWS will provide further updates as necessary to keep the public informed and support sustainable and reliable water-resource management.
For more information, contact:
Wisane Mavasa
Spokesperson for the Department of Water and Sanitation
Cell: 060 561 8935
Email: mavasaw@dws.gov.za
Maria Lebese
Gauteng DWS: Communication
Cell: 082 611 9264
Email: lebesem@dws.gov.za
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