Suspended silt concentrations in the lower Olifants River (Mpumalanga) and the impact of silt releases from the Phalaborwa Barrage on water quality and fish survival

Abstract

Silt load in the Olifants and Sabie river systems inside the Kruger National Park, were monitored. The variation in silt concentration, changes in selected physico-chemical water quality variables and fish mortalities during flushing of the Phalaborwa Barrage, were also monitored. The Olifants River inside the Kruger National Park carried high silt loads in summer. It was apparent that silt loads released from the Phalaborwa Barrage led to large variations in the natural silt loads of the Olifants River. These increased amounts of silt caused drastic reductions in the dissolved oxygen concentration of the water, ranging from >6 mg/l to 0 mg/l. Depending on the severity and duration of the flushing, fish succumb to such silt loads. -from Authors