Glomma

Glomma / Glåma
River
Glomma at Solbergfoss power plant, Østfold
Name origin: Old Norse, Glaumr, from raumr: "noise," "racket"
Country	Norway
Tributaries
- left	Vorma
- right	Rena
Source	Aursund
- location	Røros, Sør-Trøndelag, Norway
- elevation	690 m (2,264 ft)
- coordinates	62°37′06″N 11°48′11″E / 62.61833°N 11.80306°E / 62.61833; 11.80306
Mouth	Fredrikstad
- location	Fredrikstad, Østfold, Norway
- elevation	0 m (0 ft)
- coordinates	59°13′04″N 10°55′51″E / 59.21778°N 10.93083°E / 59.21778; 10.93083Coordinates: 59°13′04″N 10°55′51″E / 59.21778°N 10.93083°E / 59.21778; 10.93083
Length	621 km (386 mi)
Basin	42,000 km2 (16,216 sq mi)
Discharge
- average	720 m3/s (25,427 cu ft/s)
- max	4,700 m3/s (165,979 cu ft/s)
Glomma route

The Glomma, or Glåma, is the longest and largest river in Norway. The 621-kilometre-long (386-mile) river has a drainage basin that covers a full 13% of Norway's area, all in the southern part of the country.

At its fullest length, the river runs from the lake Aursund near Røros in Sør-Trøndelag and runs into the Oslofjord at Fredrikstad. Major tributaries include the Vorma River, which drains Lake Mjøsa, joining the Glomma River at Nes. The Lågen drains into Lake Mjøsa, collecting drainage from the large Gudbrandsdalen and significantly increasing the Glomma's flow.

Because it flows through some of the richest forest districts, it has historically been Norway's leading log-floating river. The combination of raw materials, water power, and easy transport has over the centuries encouraged industry along the Glomma. Some of the country's largest manufacturing and processing concerns are found around its mouth, where supplies of timber and hydropower have been backed by excellent port facilities.

The upper limit of the Glomma valley farms is variable, but typically runs about 500 metres (1,600 ft) in Østerdalen, slightly lower than in the Gudbrandsdalen, which reflects the colder climate. The treeline, with a light birch forest, rises to about 900 metres (3,000 ft) in Østerdalen. Above Røros the forest is restricted to the valley floor.

The upper river valleys of Norwegian rivers have distinctive names which are vestiges of earlier cultural distinctions such as building styles, traditional clothing or bunad and domestic crafts. The upper valley of the Glomma is the Østerdal (or East Valley).

Upon entering Lake Øyeren at Fetsund, the Glomma has formed Europe's largest inland delta which reaches the opposite side of the lake, across its short axis. Some of the vast amount of silt that the Glomma deposits in Lake Øyeren is extracted to manufacture LECA building blocks widely used for in the construction of foundations in Norway.