Thjórsá(thyōrs`ou'), Icelandic Þjórsá, longest river of Iceland, c.150 mi (240 km) long. It rises on the eastern slopes of the Hofsjökull and flows SW to the Atlantic Ocean.
a river in southwestern Iceland. With a length of 230 km, the Thjórsá is the longest river in Iceland, and it drains an area of 7,530 sq km, of which some 1,200 sq km are covered with glaciers. The river rises from the plateau in the center of the country. A number of the river’s right tributaries originate at the edge of Hofsjökull (a glacier). The Thjórsá forms many waterfalls; the Háfoss, the largest waterfall in Iceland (approximately 130 km high), is on the Fossa, one of the Thjórsá’s tributaries. The river empties into the Atlantic Ocean.
The Thjórsá has a mean flow rate of 390 cu m per sec. The Burfell Hydroelectric Power Plant, which has a capacity of 210 MW, is situated along the middle course of the river. In winter, the upper course of the river freezes.