The Vaal Dam, on the Vaal River at the border of the Free State and Gauteng provinces, is one of South Africa’s most strategically important reservoirs. Construction started during the Depression and the dam was completed in 1938. It has since been raised twice — in the early 1950s and again in 1985 — bringing its full supply capacity to 2,609 million cubic metres (Mm³), making it South Africa’s fourth-largest dam by volume and second-largest by surface area.
Its lake covers approximately 320 km² with more than 800 km of shoreline, making it one of the country’s most popular inland recreation destinations.
Why It Matters for Gauteng
The Vaal Dam is the primary surface water storage reservoir for the Integrated Vaal River System (IVRS), which supplies water to roughly 16 million people in Gauteng, plus parts of North West, Free State, and Mpumalanga. The Lesotho Highlands Water Project supplements supply by transferring water into the system by gravity from Lesotho’s highlands.
When the Vaal system drops below ~50% combined capacity, Rand Water introduces water restrictions for Gauteng. During the 2017–2018 drought, levels fell below 30%, triggering severe restrictions across the province.
Current Level
As of 11 June 2026: 104.9% — Spilling over
Week-on-week change: -1.0 pp on the week
Inflow: 51 m³/s | Outflow: 17 m³/s
Full supply capacity: 2,609 Mm³
The Vaal Dam is sitting at 105.1% capacity as of 4 May 2026, up 0.4 percentage points on the week. At that level the dam is above full capacity and actively spilling, which is good news for downstream water security. It has been a solid week for the catchment area.
The Vaal Dam is currently sitting at 110.6% capacity as of 12 May 2026, well above full supply level. With one sluice gate open, inflow is running at 186 m³/s against an outflow of 147 m³/s, meaning water is actively being released to manage levels. Good news for the region heading into the dry winter months.
110.6% with net positive inflow is actually notable for this time of year. Doing the rough math, 186 m³/s in against 147 m³/s out means the dam is still gaining around 39 m³/s net even with the sluice gate open. At that rate they’ll probably need to open more gates soon, otherwise levels keep climbing.
As someone in Pretoria, I track these numbers fairly closely because Vaal feeds directly into Rand Water, which supplies most of Gauteng’s taps. Rand Water pressure at my place has been noticeably more consistent this year compared to last summer when load shedding was hammering the pump stations.
Does anyone know if Rand Water publishes real-time abstraction data anywhere publicly? Would love to pull that into a Home Assistant dashboard alongside the dam level, just to see how quickly drawdown responds to consumption spikes during peak morning hours.
As of 28 May 2026, the Vaal Dam is at 106.9% capacity, down 1.3 percentage points from last week. It is still above full capacity and actively spilling, with 1 sluice gate open, inflow at 67 m³/s and outflow at 133 m³/s.
The Vaal Dam stood at 105.9% capacity as of 4 June 2026, down one percentage point on the week but still well above full, so the sluice gates remain open and the dam is actively spilling. Inflow is currently measured at 56 cubic metres per second while outflow is much lower at 4 cubic metres per second.
As of 11 June 2026 the Vaal Dam is at 104.9% capacity, which is down one percentage point from last week, but it remains comfortably above full capacity with the sluice gates open and water actively spilling. Inflow is currently at 51 cubic metres per second while outflow is at 17 cubic metres per second.
Spilling over
+0.4 pp
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-0.3 pp