Unified Deep Water System of European Russia

The Unified Deep Water System of European Russia (Russian: Единая глубоководная система Европейской части Российской Федерации) or UDWS (Russian: ЕГС) is a system of inland waterways in Russia linking the White Sea, the Baltic Sea, the Volga River, Moscow, the Caspian Sea and—via the Sea of Azov—the Black Sea. In 2010, UDWS carried 70 million tons of cargo and 12 million passengers, making up two-thirds of overall inland waterway traffic volume in Russia. There are 60 common-use ports and quays on UDWS, including 3 international ports (2 in Moscow and 1 in Dmitrov, Moscow Oblast). Owing to UDWS, Moscow is sometimes called "the port of the five seas".

The depth throughout the system was targeted at 4.5 metres (15 ft), allowing passage of not only river craft but many sea-going vessels including warships and even nuclear submarines. However, at present time, the depth is mostly guaranteed at the lesser 4 metres (13 ft), except the even shallower sections like Gorodets–Nizhny Novgorod at 2.5 metres (8.2 ft), Kochetovsky hydro-system–stanitsa Bagayevskaya at 3.2 metres (10 ft), and others. There are plans to increase depth of these sections to 4 m.

The system includes these waterways:

In 1999, the warty comb jelly colonized the Caspian Sea via the UDWS. The establishment of this population led to a 60% reduction in the number of sprat, which in turn led to a reduction in the population of sturgeon and seals.

In total, according to the unified federal/state agency CaspNIRKh (Russian: КаспНИРХ), about 60 alien species of plants and animals penetrated into the Caspian Sea in the 20th century, which has led to significant changes to ecosystems.

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