Usa (Pechora)

Usa
Physical characteristics
Mouth	Pechora River
Length	565 km

Usa (Template:Lang-ru; Template:Lang-kv) is a river in the Komi Republic of Russia. It is the largest tributary of the Pechora River, which it joins from the right. It is 565 km long, with a drainage basin of 93 600 km².

The Usa has an average discharge of 1310 m³/s, but this varies from a maximum of 21 500 m³/s in June to a minimum of 43,9 m³/s in April. It freezes over in October/November, and is icebound until the spring thaw begins in May or June. Its largest tributaries are, from the left: Yelets, Lemva, Bolshoy Kochmes and Koshu, and from the right: Vorkuta, Seyda and Kolva.

The river has its sources in the northern Ural Mountains, and it flows towards the southwest, roughly parallel to the mountain range. The main river is formed by the confluence of the Bolshaya Usa (Large Usa) and the Malaya Usa (Little Usa) some 30 km east of Vorkuta. The two tributaries are steep, with many rapids and waterfalls. After the confluence the main river is calm, with only a few rapids in its upper sections. Its banks here are high and cliff-like, but further downriver they become lower, wooded and boggy, except for a section around the settlement of Adak (russian: Адак), where the river cuts through the Chernyshov Hills.

Below the settlement of Sivomaskinsky (Russian: Сивомаскинский) the river gets much wider, and in its lower reaches it is from 700 meters to 2 kilometers wide. It also starts forming meanders and sand islands, and it keeps this appearance all the way to its mouth. Some 30 km from its mouth lies the town of Usinsk and the river port of Parma. The Usa flows into the Pechora River at the settlement of Ust-Usa.

The river is navigable 325 km from its mouth, and there are river ports at Abez, Petrun, Makarikha, Parma and Ust-Usa. Within the Usa basin is the large Pechora coalfield, and in its lower parts, by the town of Usinsk, there are several big petroleum- and natural gas fields.

The Usa valley has been inhabited for 40,000 years, as evidenced by the archaeological site Mamontovaya Kurya (Russian: Мамонтовой Курьи, "the mammoth curve").