Near the confluence of the Harts and Vaal River a major irrigation system, the Vaal-Harts Scheme has been set up in 1933 as part of the national renconstruction effort after the Depression.  Here water drawn from both the Vaal and the Harts rivers provide water to intensively irrigate numerous smallholdings through a system of canals in an otherwise dry area of the country, supporting towns such as Jan Kempdorp and Vaalharts. (Ref 2)

“Water in the Harts River downstream of the Vaalharts irrigation scheme is of exceptional high salinity as a result of saline leachate from the irrigation fields (± 1 100 mg/l salinity), and needs to be carefully managed through blending with fresher water. Water quality in the lower reaches of the Vaal River is also impacted upon by irrigation return flows from the Harts River as well as from the Riet/Modder River further downstream, necessitating further blending with low salinity water from the Orange River at the Douglas weir.” (Ref 4)

Ref 4:   Department of Water Affairs and Forestry, South Africa. 2004. Lower Vaal Water Management Area: Internal Strategic Perspective. Prepared by PDNA, WRP Consulting Engineers (Pty) Ltd, WMB and Kwezi-V3 on behalf of the Directorate: National Water Resource Planning. DWAF Report No P WMA 10/000/00/0304)