Þjórsá

Þjórsá at the height of Hekla, overlooking the Búrfell

Þjórsárver, headwaters of the river at the foot of Hofsjökull

The river Þjórsá [ θjour̥sau ] is located in the south of Iceland. With its 230 km, it is the longest river of the island. The catchment area of the river covers 7530 km ² or 7.2% of the total surface area of Iceland. Near the mouth of the waterfall Urriðafoss the average amount of water in the summer is 350-700 m³ / sec

Name

To the name of the river it says in the book Conquest: " Þórarinn was a man, the son of Þorkell ... He came with his ship in the Þjórsárós (which is the mouth of the Þjórsá ). He had appointed a cow head on the bow and then the river. " ( Altisl. Þjór " cattle " )

Source areas

The Þjórsá springs on the glacier Hofsjökull mainly at the glacier tongue Þjórsárjökull, where the river is called Bergvatnskvísl Þjórsár, often only Bergvatnskvísl. But you also relates water from springs in the Þjórsárdragar and of a known nature reserve, an interspersed with sources bog with names Þjórsárver. The name Þjórsá contributes to the flow of the place where the streams flow from Háöldakvísl and Fjórðungskvísl Tungnafellsjökull in him.

Course

The main flow direction follows the orientation of the rift zone from northeast to southwest.

Þjórsá makes its way partially through narrow gorges about the Icelandic highlands. She falls over several waterfalls. The overall gradient is here, at about the height of Hekla 280 m to 40 km. Man has used the enormous power of the river and its tributaries as the Tungnaá here in some power plants. The Tungnaá for example, now flows into a reservoir, Sultartangalón, in the Þjórsá. The Búrfell power plant uses the force V.A. the waterfall Tröllkónuhlaup, who is now almost dried up, because is allowed to flow in channels through the mountain Búrfell part of the water where the water force drives the turbines in a turbine house situated beyond. In the year 2012, is just another power plant on Budarhals under construction.

Later, after she has taken up the tributary Tungnaá near the historic farm Stong (see also Háifoss ), flows through the Þjórsá in the level and wide through various lava fields, including the 8000 years as Tungnaárhraun, then.

After that, she branched more frequently and forms small islands. Middle of the river is about the island Árnes, which was a headland earlier. On it there is an old Thingstätte. After the island is also the county Árnessýsla is named.

Between Selfoss and Hella crossed above the falls Urriðafoss the ring road ( Hringvegur ) the bridge over the river, which it joins a few kilometers south-west into the sea.

Floods and droughts

The Þjórsá prone to significant flooding. It causes even the biggest in the country, if one disregards the glacier runs.

The largest so far measured tidal waves in the Þjórsá amounted to more than 3,000 m³ / sec in the years 1948 and 1949.

Flooding can also be due to the enormous ice formation in some winters. This was the case in the winter of 2006 /2007. In this form, for example, ice barriers on bridges, behind the dam the water and thus flooding auslösen.Solche phenomena are also other rivers in Iceland in winter are not uncommon such as in the Hvítá in Borgarfjorður. This Hofbewohner to islanders can be.

It has however also been found to droughts. Thus, their average amount of water was reduced to only 20 m³ / sec in April 1963.

Glacial river

For the most part Þjórsá is a glacial river. It flows also on long distances over desert-like erosion areas in the highlands. This means that it carries large amounts of sediment with it.

Obstruction

In the past, the river was a significant impediment to traffic. He is so today in the highlands, where there is only one viable ford Sóleyjarhöfðavað. If this is not to commit to cross people who are traveling in the highlands, and over must, for example, in search of sheep or hiking, the individual tributary streams to the north.

We made ​​use of earlier boats to cross the river. Some Fährplätze are known, such as the already made ​​use of to land acquisition times Sandhólaferja.

The first bridge across the river is dated from 1895, it was renewed in 1949 and leads the ring road near the waterfall Urriðafoss. Another bridge stands in the highlands at the power plants. Here the highland road sprengisandur begins.