linguistic:voice_change, structural:summarization
Description

The Volga is the longest river in Europe, and its catchment area is almost entirely inside Russia, though the longest river in Russia is the Ob – Irtysh river system. It belongs to the closed basin of the Caspian Sea, being the longest river to flow into a closed basin. The source of the Volga lies in the village of Volgoverkhov'e in Tver Oblast. Rising in the Valdai Hills 225 meters (738 ft) above sea level northwest of Moscow and about 320 kilometers (200 mi) southeast of Saint Petersburg, the Volga heads east past Lake Sterzh, Tver, Dubna, Rybinsk, Yaroslavl, Nizhny Novgorod, and Kazan. From there it turns south, flows past Ulyanovsk, Tolyatti, Samara, Saratov and Volgograd, and discharges into the Caspian Sea below Astrakhan at 28 meters (92 ft) below sea level.

The Volga has many tributaries, most importantly the Kama, the Oka, the Vetluga, and the Sura. The Volga and its tributaries form the Volga river system, which flows through an area of about 1,350,000 square kilometres (521,238 square miles) in the most heavily populated part of Russia. The Volga Delta has a length of about 160 kilometres (99 miles) and includes as many as 500 channels and smaller rivers. The largest estuary in Europe, it is the only place in Russia where pelicans, flamingos, and lotuses may be found. The Volga freezes for most of its length for three months each year.

The Volga drains most of Western Russia. Its many large reservoirs provide irrigation and hydroelectric power. The Moscow Canal, the Volga–Don Canal, and the Volga–Baltic Waterway form navigable waterways connecting Moscow to the White Sea, the Baltic Sea, the Caspian Sea, the Sea of Azov and the Black Sea. High levels of chemical pollution have adversely affected the river and its habitats.

The fertile river valley provides large quantities of wheat and other agricultural produce, and also has many mineral riches. A substantial petroleum industry centers on the Volga valley. Other resources include natural gas, salt, and potash. The Volga Delta and the Caspian Sea are fishing grounds.