Chemical spraying on the water lettuce and water hyacinth in the Vaal is expected to resume.
The spraying was stopped after an uproar over the use of glyphosate to kill the weeds. The chemical is said to be carcinogenic, and residents and watchdog groups, such as WaterCAN, were concerned that it had the potential to poison the potable water that is supplied to 19 million people.
Since October, the weeds have flourished to double every two weeks.