The Phongolo River rises just east of Wakkerstroom and drains an area of nearly 8,000 km² where the rainfall often exceeds 1,000 mm a year. Because the irrigation weir at Pongola could not fully regulate the river's erratic water flow, the 89-meter-high Pongolapoort Dam wall was built in 1972 in a narrow gorge in the Lebombo Mountains. Phongolo is the Zulu word for trough, referring to the many deep pools with steep sides along the river's course.