River Tungnaa discharges a larg area of the western part of glacier Vatnajokull, the largest one of Europe.  Its volume is sufficient to feed several hydroelectric power plants enroute, before it spills into the country's longest river, Thjorsa, where it looses its name.  During its course it collects small and large triburaries like Kaldakvisl and other smaller streams.  The landscapes along the river have been changed by man-made lakes, reservoirs for the power plants.  It has two bridges to facilitate the crossing of the interior by 4wd vehicles from south to north or vice versa.

Some of the tributaries and connected lakes count among the best fishing lakes of the country, i.e. Lake Kylingavatn, River Kaldakvisl, Lakes Veidivotn and others.