Grootdraai Dam is situated in the upper reaches of the Vaal River less than 10km upstream of Standerton. The full supply capacity of the reservoir is 364 million m3 (364 Ml). It has a catchment area of 8 195km2, a mean annual precipitation of approximately 750mm, a mean annual potential evaporation at the dam site of 1 400mm and a natural inflow of 580 million m3/a.
Grootdraai Dam is a composite structure comprising a central concrete gravity section 360m long and two earthfill flanks giving a total crest length of 2 180m and a maximum wall height of 42m above lowest foundation level. The dam was completed in 1982 and was built primarily to support the water needs of the SASOL I, II and III coal to petrol plants at Secunda, ESKOM's, Tutuka Power Station as well as the Matla, Duvha, Kendal and Kriel power stations located on the coal fields in the adjacent Olifants River basin.
The dam also provides some flood attenuation for Standerton and stores up to 100 million m3/annum pumped into the upper reaches of the Vaal River basin from Heyshope Dam in the Usutu basin.