The Great River of Thjorsa in Iceland

by : Bjorn Olav Jonsson

The benefit of receiving great rainfall and having big glaciers is that Iceland has a very rich quantity of some very big rivers. The biggest river of Iceland is Thjorsa which is 237 kilometers long and has an average discharge of 380 cubic meters per second. Whereas, River Olfusaa has the greatest flow of water with 440 cubic meters per second. The second biggest river is Jokulsa a Fjollum and it is 206 kilometers in length. Some other rivers of Iceland are Skjalfandafljot, Jokulsa a Bru, Lagarfljot, Skeiaara etc. Let's talk about the biggest river Thjorsa this time.

The ancient book of settlement has got some very interesting explanation regarding the value of this river. "A man named Thorarinn, the son of Thorkell from Alvidra, the son of Hallbjorn Hordukappi, sailed to the estuaries of this river and didn't even remove the carved bull's head from the prow of his ship". This is the longest river and the second biggest discharger of Iceland. The interesting fact is that it acts as a natural border between the districts of Rangarvellir and Arnessysla. Its northernmost tributary is called the spring fed river.

The source of this river is located around 70 kilometers towards south of the end of the Eyjafiord bay in the northern direction. The main course of this river is situated in the southwest direction which is following the main tectonic fissure of the country. The discharge area of this river is huge and it covers around 7530 square kilometers. Most of its discharge is simply the water coming from glaciers named Vatnajokull and Hafsjokull. The biggest flood recorded in this river took place in 1948-49 and the speed of the flow was as fast as 3000 cubic meters per second. Sometime in many years, this river has the tendency to almost vanish away in the lower regions of its way, especially when the ice formed in winter season melts up and creates natural dams.

This river is the carrier of great amount of sludge and exasperate from the areas of erosion based in central highlands. The amount carried by this river is somewhere around 4.5 million tons per year. Some waterfalls are also created by this river before it goes down and vanishes in ocean. Its largest tributary is Tungnaa and it is said that it is even bigger than the river Thjorsaa at its convergence. In ancient times all the rivers of Iceland were great barriers for those who used to cross them with ferries. All the fords of this river are above its biggest island named Arnes. There are many ferry stations on its way and the farmers living close to them give their assistance to the travelers against money.

The first bridge was constructed on this river in 1895 and it was renovated or we can say, rebuilt again in 1949. Another bridge was built on this river in 1973 with the link of construction of a hydro-electric power station on the tributary Tungnaa. Dams and power stations built on this river and its tributaries contribute more than 27 percent to Iceland's total electricity production.

This river has been the forgotten lifeline of the country of Iceland and its people. With the passing time, they have realized the importance of the river and various resources available in it.