Across the full week, inflow ranged between a high of 49.3 m3/s and a low of 44.1 m3/s, averaging 47.5 m3/s.
The Vaal Dam wall is seen with during a period of heavy rains on 3 January 2021. Picture: Michel Bega
The Vaal Dam remained more than 100% full for this week.
This comes even as inflows into the dam declined steadily through the period, according to data from The Reservoir, a Water Resource Information Centre for the Catchment Management Forums of the Upper Vaal Water Management Area.
Storage levels dropped slightly from 102.53% on Monday to 102.02% by Friday, the weekly hydrological report showed.
Full Vaal Dam levels this week
On Monday, 20 July, inflow into the dam measured 49.3 m3/s, storage stood at 102.53% full, discharge was recorded at 16.9 m3/s, and no sluice gates were open, the report showed. On Tuesday, 21 July, inflow eased slightly to 47.8 m3/s, storage dropped to 102.40%, discharge held at 16.9 m3/s, and sluice gates remained closed.
By Wednesday, 22 July, inflow rose marginally to 48.5 m3/s, storage fell further to 102.27%, discharge stayed unchanged at 16.9 m3/s, and no gates were opened, according to The Reservoir’s figures.
On Thursday, 23 July, inflow dipped to 47.9 m3/s, storage stood at 102.14%, discharge remained steady at 16.9 m3/s, and sluice gates were still closed.
Inflow fell to its lowest point of the week on Friday, 24 July, at 44.1 m3/s, storage dropped to 102.02%, discharge again held at 16.9 m3/s, and no sluice gates were opened, the data indicated.
Across the full week, inflow ranged between a high of 49.3 m3/s and a low of 44.1 m3/s, averaging 47.5 m3/s.
Storage ranged from a high of 102.53% to a low of 102.02%, averaging 102.27% for the week, while discharge held steady throughout at 16.9 m3/s.
Barrage discharge fluctuated through the week
At the Vaal Barrage, water levels held steady at 7.5 metres throughout the week, but discharge rates swung considerably, the data showed.
Discharge started at 5.0 m3/s on Monday, climbed to a weekly high of 22.6 m3/s by Wednesday, held near that level on Thursday at 22.5 m3/s, then dropped to 15.1 m3/s on Friday.
Water temperature at the barrage rose gradually across the week, moving from 11.0°C on Monday to 12.0°C on Friday, with a peak of 12.6°C recorded on Thursday, according to The Reservoir.
The information was supplied on behalf of Rand Water and the Department of Water and Sanitation, and it was noted that not all abstraction and evaporation losses from the Vaal Dam were reflected in the figures.
