(and that's no racialist statement! :)
Gullfoss detail.
The river Hvitá (White river) is 155 km long, draining southwards from the lake Hvitárvatn, a 30 km²/84m deep lake on the eastern side of Langjökull,
the 2nd largest glacier in Iceland. Average summer water-flow is 140 m³/s, in winter 80 m³/s, while the highest flood ever measured was a whopping 2000 m³/s!