Vaal Dam stays full at 100% despite steady fall in inflows

Vaal Dam was 100% full on Friday, 4 September 2026, even as inflows into the reservoir declined through the week, the weekly hydrological report compiled for Rand Water and the Department of Water and Sanitation (DWS) shows.

Storage fluctuated but stayed at full capacity

The report recorded the dam’s storage opening the week at 100.63% on Monday, then falling to 100.38% on Tuesday, 100.35% on Wednesday and rising slightly to 100.41% on Thursday before settling at 100% on Friday. The weekly average storage was 100.35%, with a high of 100.63% and a low of 100%. The DWS noted the level on Friday represented a drop from the same week last year when the dam stood at 106.7%.

Inflows fell daily; discharge steady

Inflow to Vaal Dam fell on most days, starting at 43.7 m³/s on Monday, dropping to 39.3 m³/s on Tuesday and to 38 m³/s on Wednesday. Thursday saw a small rise to 42.6 m³/s, followed by the week’s lowest inflow of 25.7 m³/s on Friday. The weekly average inflow was recorded at 37.9 m³/s.

Despite the falling inflows, discharge from Vaal Dam remained constant at 16.8 m³/s each day from Monday to Friday. The report also states that no sluice gates were opened on any day of the week.

Vaal Barrage conditions

The Vaal Barrage held a consistent level of 7.5 metres from Monday through Friday, with discharge at the barrage steady at 22.6 m³/s. Water temperature at the barrage varied during the week, from 12.6°C on Monday to a high of 16.4°C on Tuesday and Thursday, falling slightly to 16.2°C on Friday. The weekly average temperature was 15.4°C.

Data caveat

The report cautions that not all abstraction and evaporation losses from Vaal Dam were reflected in the figures, and that weekend data remained unverified pending confirmation.