South Africa’s largest water supply reservoir remains above 100% capacity for a third consecutive day, with authorities gradually ramping up releases as inflows continue to exceed outflows.
Vaal Dam holds above full supply level despite three-day decline
The Vaal Dam ended the three-day reporting period still well above its full supply level, though its percentage has edged lower each day.
The reservoir stood at 105.23% on 8 June 2026, according to data from The Reservoir, a Water Resource Information Centre for the Catchment Management Forums of the Upper Vaal Water Management Area.
The reservoir recorded the dam’s level easing to 104.96% on 9 June before slipping further to 104.84% on 10 June.
Despite the gradual decline, the dam remained comfortably above capacity throughout, with no flood gates opened on any of the three days.
Inflows held relatively steady across the period. “Inflow: 64.0m³/s,” The Reservoir reported for 8 June, with outflow held at just 3.8m³/s and gates remaining shut.
The following day saw inflows edge higher, with The Reservoir noting: “Inflow: 66.8m³/s,” while outflow remained unchanged at 3.8m³/s.
Outflow jumps fivefold
The most significant operational change occurred on 10 June, when outflow from the Vaal Dam was sharply increased.
While inflows eased slightly to 58.4m³/s, outflow was raised to 20.4m³/s.
The Reservoir captured the shift clearly in its daily reading: “Outflow: 20.4m³/s,” with the dam still recording no open gates.
The increased releases appear to be a managed response to the sustained above-capacity storage, aimed at gradually drawing the level down while avoiding a sudden surge through the spillway.
The incremental approach to increasing outflow, with gates remaining closed across all three days, suggests controlled balancing of the system. “Gates Open: 0,” The Reservoir confirmed consistently across the 8, 9 and 10 June entries.
Vaal Barrage water levels and temperature climb steadily
Downstream, the Vaal Barrage reflected the gradual increase in releases from the dam, with its level rising incrementally over the three days.
The Reservoir reported the barrage sitting at 7.4 metres on 8 June, climbing to 7.5 metres on 9 June and reaching 7.6 metres by 10 June.
Outflow at the barrage also increased in step with the upstream changes.
“Outflow: 5.0m³/s,” The Reservoir noted on 8 June, rising to 5.1m³/s the following day. By 10 June, as the higher dam releases began to move downstream, barrage outflow had climbed to 15.2m³/s.
Water temperature at the barrage showed a notable warming trend across the period.
The Reservoir recorded temperatures rising from 12.4°C on 8 June to 12.9°C on 9 June, then to 14.5°C on 10 June, a rise of more than two degrees over the three-day window. “Water Temp: 14.5°c,” The Reservoir confirmed for the final day of the reporting period.
