Núpsárfoss is a gorgeous waterfall in the south of Iceland but difficult to reach. When the rivers Núpsá and Hvítá join each other in two gorgeous waterfalls (Núpsárfoss and Hvítárfoss) the river course is called Núpsvötn. The river is fed by the glacier Skeiðarárjökull and can rise enormously and causes big floods from lake Grænalón by the edge of Skeiðarárjökull.
In the first part of the 20th century the water volume was massive, appr. 5.000-10.000 m³/sec. These days it will peak at approx. 2.000 m³/sec, which still is considerably.
The valley between Lómagnúpur and Skeiðarársandur,Núpstaður, is very attractive but difficult to reach. It is possible to hike along the eastern side of the canyon, but isn’t easy. From road 1 it is a 1 day hike.
It is also possible to drive (partially) , but the track between the main road and the woods requires a 4WD and experience in crossing wild rivers. Sometimes it is impossible to cross the river because of the heavy flood.
I have read that there is also a possibility to go by bus from Núpstaðarskógur. More info is available at Kirkjubæjarklaustur.