The accurate measuring of flow in rivers is essential for optimal utilisation of the surface water resources in South Africa. Long-term hydrological records containing the characteristic parameters of change and variability are required for the effective management and conservation of scarce water resources. The runoff from catchments is measured by using gauging structures in rivers and at dams. In South African rivers, the use of compound gauging weirs is common due to the large variation in flows. This allows for accurate measuring of discharge in a river section at low and high flow rates (Wessels & Rooseboom 2009).