Water and Sanitation on flood-management operations at Vaal and Bloemhof Dams

The Department of Water and Sanitation has noted the statement issued by the Democratic Alliance on 17 November 2025 regarding the Minister of Water and Sanitation’s alleged “lax attitude” to flood risk at the Vaal Dam. The statement misrepresents both the Minister’s reply to Parliament and the technical flood-management rules that govern the operation of Vaal and Bloemhof Dams.

The Vaal and Bloemhof Dams form part of the integrated Vaal River System and are operated in terms of approved technical guidelines. These guidelines require the Department to balance three key objectives: protection of dam safety, reduction of downstream flood risk as far as is practically achievable, and safeguarding reliable water supply for domestic, industrial, and agricultural users, including users along the Lower Orange River and in Namibia.

The “100%” level that is reported publicly is the full supply level which is critical for long-term water availability planning, not necessarily a safety limit. Both dams are designed with a temporary flood-absorption zone above 100%, which is precisely to be used during high inflows.

It should be noted that the integrated Vaal River System is currently in a deficit and will only be returned to a long-term balance between water supply availability and the projected requirements once Phase 2 of Lesotho Highlands Water Project, which is currently under construction, delivers additional water into the system by about 2028. Until then, it is critical to maintain the dam levels in a healthy state to ensure long-term water security especially during drought situations, while managing short term flooding situations as necessary.

The Minister’s earlier reply to Parliament was given at a time when inflows into the Vaal Dam were low and stable, and no significant flood-producing rainfall was present in the short-term weather forecasts. Under such conditions, pre-emptively releasing large volumes of water simply because the dam was above 100% would have been contrary to the water security objectives and Technical Guides for Flood Management in the Vaal–Orange River System, which cautions against lowering dams based on seasonal weather forecasts alone.

Reference to evaporation and normal water use was made in that context and never presented as the sole flood-management measure. Between the end of the 2024/25 flood season and the beginning of the 2025/26 flood season, the dam levels did reduce from around 110% to 100-101% due to evaporation and water use. This was in line with the projected dam levels trajectory.

The rainfall season has now begun and hydrological conditions have changed over the past few days, and operations have been adjusted accordingly. At the Vaal Dam, due to the current rains, inflow has increased from about 250 m³/s yesterday morning to an estimated 1019 m³/s today. In anticipation of these higher flows, outflows were first increased from 60 m³/s to 700 m³/s by opening five sluice gates on Monday. On Tuesday, up to eight gates will be opened so that releases can approximately match the incoming flows and the dam level can start to recede. The Vaal Dam level has risen from around 104% to about 109%, and releases will be sustained and adjusted as needed to bring the level back down into the target operating range of 100–103%.

Bloemhof Dam is currently at approximately 99,8% of capacity. To create space ahead of the additional water moving down from Vaal Dam, the outflow at Bloemhof was increased from 250 m³/s to 400 m³/s on Monday, and will be further increased to around 600 m³/s today. It typically takes about three days for water released from Vaal Dam to reach Bloemhof Dam. These actions are specifically intended to keep Bloemhof as low as possible in anticipation of the higher inflows expected from upstream, while keeping downstream flows within ranges that previous events have shown to be manageable.

Decisions on dam releases are based on real-time inflow measurements, river-routing models, and close coordination with disaster-management structures, not on political considerations. The Department will continue to operate the Vaal–Orange River System strictly in line with the approved technical guidelines, adjusting releases as conditions change, and will keep the National Disaster Management Centre, provinces, municipalities, and affected communities informed as the rainy season progresses. Far from being “lax”, these operations reflect an active, adaptive approach to managing flood risk and water security in a complex, highly utilised river system.

Enquiries:
DWS head of communications
Dr Mandla Mathebula
Cell: 083 235 8675
E-mail: MathebulaM@dws.gov.za

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