The Volga–Baltic Waterway, formerly known as the Mariinsk Canal System (Russian: Мариинская водная система), is a series of canals and rivers in Russia which link the Volga River with the Baltic Sea. Its overall length between Cherepovets and Lake Onega is 368 kilometres (229 mi).
Originally constructed in the early 19th century, the system was rebuilt for larger vessels in the 1960s, becoming a part of the United Deep Inland Waterway System of European Russia.
After Peter the Great wrested the Gulf of Finland from Sweden, it was necessary to provide a secure means of river transportation with the Russian hinterland. The earliest Vyshny Volochyok canal system, completed by 1709, was intended to provide for this. It was followed by the ambitious project of the Ladoga Canals.
Under Alexander I of Russia, the traditional waterway through Vychny Volochyok was complemented by the Tikhvin canal system (1811) and the Mariinsk canal system (1810), the latter becoming by far the most popular of the three.
The Mariinsk canal system was an outstanding monument of early 19th-century hydrotechnics, which proved to be of vital importance to the national economy. The system started in Rybinsk and passed through the Sheksna River, Lake Beloye (and Belozersky bypass canal), Kovzha River, the artificial Novomariinsky Canal, the Vytegra River to Lake Onega. Thereupon vessels sailed through the Onega Canal, the Svir River, the Ladoga Canal, and the Neva River to the Gulf of Finland.
In 1829, the Northern Dvina Canal was opened; it connects the Sheksna River (one of the Volga's tributaries) through the Kubenskoye Lake with the Northern Dvina, flowing into the White Sea. In the following decades, the system was further expanded: three more canals, Belozersky, Onezhsky, and Novoladozhsky, enabling smaller craft to bypass dangerous waters of the three big lakes (Beloye, Onega, and Ladoga), were inaugurated towards the end of the century.
In recent years, the Volga–Baltic Waterway has gained additional importance as a tourist route for boats sailing along the Silver Ring of Russia.
Volga–Baltic Canal improvement 
In Soviet time, the Mariinsk canal system was constantly improved. Two locks were built on the Svir River (in 1936 and 1952); 3 locks were built on the Sheksna River. Major improvement of the Volga–Baltic Waterway took place in 1960–1964, and the new Volga–Baltic Waterway was opened on June 5, 1964. 39 old wooden locks were replaced with 7 new locks, and one parallel lock was built later in 1995. The locks' limiting dimensions are 210 m long, 17.6 m wide and 4.2 m deep, allowing passage of river-sea ships of up to 5000 tons displacement. Such ships were able to sail directly across the big lakes instead of using the bypass canals. Typical travel time for Cherepovets – Saint Petersburg route decreased to 2.5–3 days from 10–15 days.
The new canal route somewhere follows the route of old Mariinsk system, somewhere diverges from it. 6 of canal's 8 locks are located along 35 km of the northern slope, with a total lift of 80 meters. The only 2 locks (parallel) on the southern slope, with a lift of 13 meters are located near Sheksna on Sheksna River, 50 km upstream from Cherepovets. The canal route on the northern slope follows the Vytegra River flooded riverbed. The summit pound of the canal between Pakhomovo locks on Vytegra River and Sheksna Reservoir dam is 278 km long. It includes artificial divide canal ( 40 km long), Kovzha River, Lake Beloye and Sheksna River. The route of the southern slope follows the Sheksna River, where it is in the backwater area of Rybinsk Reservoir.
Current developments 
The canal is actively used for oil and lumber export and as a river tourism route. According to the Maritime Board (Morskaya Kollegiya) of the Russian Government, 17.6 million tons of cargo were carried over the Volga–Baltic Waterway in 2004, which is very close to the waterway's maximum capacity. The Lower Svir Lock was one of the two busiest locks on Russia's inland waterways (the other one was the Kochetov Lock on the lower Don River).
At the same time, as stated by a former Soviet inland waterways official to the Gudok newspaper in September 2006, the Volga–Baltic Waterway had suffered from deferred maintenance over the previous years. "During more than 7 years" (i.e. 1999–2006), no dredging had been done; as a result, the guaranteed channel depth had decreased from 4 m to 3.5 m, and the guaranteed channel width, from 80 m to 25 m meaning that vessels greater than 4,000 tons could not make it through the canal anymore. Travel times through the canal had lengthened from 3–3.5 days to 7 days. The locks needed repairs as well.
- СУДОХОДСТВО НА БЕЛОМ ОЗЕРЕ ДО И ПОСЛЕ ПРОРЫТИЯ БЕЛОЗЕРСКОГО ОБВОДНОГО КАНАЛА
- Морская коллегия: Речной транспорт (Maritime Board: River Transport) (Russian)
- Bagrov, Leonid (2006-09-11). "Единая глубоководная система России в шаге от катастрофы" [Russia's United Deep Inland Waterway System is on the brink of a disaster]. Gudok. Retrieved 2012-10-22. Mr. Bagrov is Director General of Russia's Tanker Union, and former Minister of River Fleet of the RSFSR.
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- Volga-Baltic waterway on Infoflot site (Russian)