Vaalhartz Weir (alternative spelling) is located on the Vaal River approximately 100 km downstream of Bloemhof Dam and 13 km upstream of Warrenton.
Water is also used for numerous small towns including Vryburg, Hartswater, Jan Kempdorp, Warrenton, Winsorton, Kipdam, Barkly West and Delportshoop.
The main construction of the weir was completed in 1938 and was part of the government initiatives to alleviate unemployment following the depression of the 1930s.
The sluices are of two types; some for the normal river releases and some for flood management purposes.
It diverts water into a concrete lined canal on the right flank with a capacity of 40 m³/s.