The Danube Delta is the wetland where the Danube, after a 2,850 km run past or through ten countries, splits into three main branches and enters the Black Sea, mostly in Romania’s Tulcea County, with its northern edge in Ukraine’s Odesa Oblast. The delta proper covers about 4,152 km², of which 3,446 km² are Romanian; adding the Razim–Sinoe lagoons to the south brings the total to 5,165 km². After the Volga Delta it is the second-largest delta in Europe and the best preserved, a low maze of channels, reed beds, lakes and floating reed islands averaging just 0.52 metres above sea level. The Romanian part became a UNESCO World Heritage Site in 1991, the delta is a Ramsar wetland, and since 1998 a 6,264 km² biosphere reserve has been shared by Romania and Ukraine. The best way to understand it is to travel it, branch by branch, from the city at its western gate to the sea.
Tulcea and the First Fork
Every journey into the delta begins at Tulcea, the county seat at the delta’s western edge, with 65,624 inhabitants in 2021. The town was founded as Aegyssus in the 7th century BC and later served as a Roman fort and port for the Danube fleet. Today it is the hub of the region and the gateway to the delta, the place from which nearly every boat trip downstream begins.
Upstream of the town, the river makes its first great split. The northern arm becomes the Chilia branch; the southern one, the Tulcea branch, flows past the town and divides again further downstream into the Sulina and Sfântu Gheorghe branches. The Danube arrives at the head of the delta carrying about 6,350 cubic metres of water per second, and roughly half of it goes north into the Chilia.
Down the Chilia Branch, Romania’s Border with Ukraine
The Chilia is the delta’s northern branch and its most powerful. For most of its course it forms the border between Romania and Ukraine, following the Kilia and Old Stambul channels, the line set between Russia and Romania in 1878. The branch takes its name from the twin towns that face each other across it, Kiliia on the Ukrainian bank and Chilia Veche on the Romanian one; further upstream stands Izmail, the largest town of the Ukrainian delta.
Geologically the Chilia is the youngest of the three arms, around 2,000 years old. For much of that time it emptied into a lagoon called the Thiagola, and only after about 1000 CE, when the lagoon filled with sediment, did it reach the sea directly. By the late 14th century it had become the main shipping route across the delta, with a Genoese trading post on its banks. It is also the most vigorous of the three: since around 1600 AD the Chilia has been building its own lobe of new land into the Black Sea, and a microdelta is forming at its end today.
Near the sea the branch reaches Vylkove, founded in 1746 and home to 7,712 people in a 2022 estimate. Its canals, dug through the town, earned it the name “Ukraine’s Venice”, and boats remain the usual way to get around. About 70 percent of the town was Lipovan at the 2001 census: descendants of Old Believers who fled religious persecution in Russia in the 18th century. The administration of Ukraine’s Danube Biosphere Reserve is based here.
Bystroe: Ukraine’s Deep-Water Channel to the Sea
Near Vylkove the Chilia splits again, and one of its mouths became a diplomatic dispute. Ukraine lost its own deep-water route to the Black Sea when the Prorva distributary silted up in 1997, leaving its shipping dependent on the Romanian-controlled Sulina channel. In 2004 it began dredging the Bystroe distributary, which runs through Ukrainian territory inside the Danube Biosphere Reserve. Romania objected on ecological grounds, the European Union advised Ukraine to halt the work, and Romanian officials threatened to take the case to the International Court of Justice. The channel was declared open on 10 May 2007 for ships with a draft of up to 4.5 metres. The Chilia has also become a major route for Ukrainian shipping since the country’s Black Sea ports became targets during the Russian invasion.
Along the Sulina Branch: Crișan and Mila 23
Back at the second fork below Tulcea, the central arm, the Sulina branch, is the delta’s highway. It is the shortest route to the sea and carries only about 20 percent of the Danube’s flow, yet it has been engineered more than any other channel. Under the Treaty of Paris of 1856, which ended the Crimean War, the European Commission of the Danube was set up to make the river mouth navigable. Jetties were built at the Sulina mouth from 1858 to 1872 and later lengthened to reach 9,300 metres from the shore, and work to straighten the channel began in 1862, cutting out many of the bends of its winding original course of more than 80 km. Together the works more than doubled its flow and made it fit for large ships.
The channel passes through the commune of Crișan, about 50 km downriver from Tulcea, which takes in the villages of Crișan, Caraorman and Mila 23 and had 1,092 inhabitants in 2021. The commune has an unusual claim: it has produced a long line of sprint canoeists, among them Ivan Patzaichin, who won four Olympic gold medals. At Mila 31, near the village of Partizani, the Ukrainian-flagged vessel Rostock sank in 1991 and partly blocked the channel; the last piece of the wreck was raised only in 2015.
On either side of the channel lies the delta’s interior: reed beds, floating plaur islands of tangled reed roots and soil, and lakes such as Dranov (21.7 km²), Roșu (14.5 km²) and Gorgova (13.8 km²), the three largest. Most of the delta is less than a metre above sea level, and about a fifth of it lies below.
Letea and Caraorman: Forests on the Dunes
Between the Chilia and Sulina branches, the land rises in a way that surprises most visitors. The Letea strand plain carries sand dunes up to 12.4 metres high, and the Caraorman strand plain, south of the Sulina, reaches about 7 metres.
Letea Forest, about 2,825 hectares of oak, ash, poplar and elm growing in the hollows between the dunes, became Romania’s first nature reserve in 1938. Climbing plants give it a subtropical look, among them Periploca graeca, a Mediterranean vine that reaches its northernmost refuge here. The forest is also home to feral horses: about 4,000 roam the delta, around 2,000 of them at Letea. Their numbers rose sharply after the collective farms closed in 1990 and their horses were turned loose, and they are now a concern because their grazing threatens rare plants.
Sulina, Where the Middle Branch Meets the Black Sea
The Sulina branch ends at the town of Sulina, the easternmost point of Romania and the only settlement with an urban character in the Romanian delta. It grew from a 14th-century Genoese harbour and an 18th-century Ottoman lighthouse into a busy transshipment port after the Treaty of Adrianople in 1829 freed the Danube grain trade. The Ottoman administration declared it a free port in 1870, and in 1878 it passed to Romania with the rest of northern Dobruja. In the early 2000s about 20,000 people lived in the Romanian delta, roughly 4,600 of them in Sulina; the rest are scattered among 27 villages.
North of the town, Musura Gulf is one of the best examples of what biologists call the beforedelta, the zone where fresh river water and salt sea water meet and mix.
The Sfântu Gheorghe Branch and the Sacalin Islands
The southern branch, the Sfântu Gheorghe, carries about 22 percent of the river’s flow and is the oldest and most sparsely populated of the three. Cutting through six large meanders shortened it by roughly 40 km. It is also the key to how the whole delta formed. The modern delta began after about 4000 BC, when the Black Sea rose to its present level and a sandy barrier closed off a Danube bay. Once the bay had filled, the river pushed out to sea in successive lobes: St George I (3500–1600 BC), Sulina (1600 BC to the start of the Common Era), St George II (from then to the present) and the Chilia lobe (from about 1600 AD). The geologist Liviu Giosan has estimated that probably 40 percent of the delta was built in the last 1,000 years, largely from soil eroded after forests were cleared upstream.
The branch ends at the fishing village of Sfântu Gheorghe, which appears as San-Giorgio on the Genoese cartographer Visconti’s map of 1318. Offshore, sediment from the branch has built the Sacalin Islands since 1897; they now stretch for 19 km. The delta as a whole is pelican country. More than half of all Eurasian great white pelicans breed in the Danube Delta, and some 450 pairs of the rarer Dalmatian pelican nest here too. The delta holds over 320 bird species in summer, and more than a million birds spend the winter.
Razim–Sinoe: The Lagoons at the Southern Edge
South of the Sfântu Gheorghe branch, the journey ends in open water. The Razim–Sinoe complex of lagoons covers about 1,015 km², 865 km² of it water, and is geologically part of the delta and inside the World Heritage Site. Lake Razim alone covers about 400 km², the largest liman in Romania. When the Razim and Golovița system was closed off from the sea in the late 1970s, its salinity fell almost to zero and eutrophication followed, but Popina Island at its northern end remains an important refuge for birds.
The lagoons also show what the delta has lost. Under the communist regime large areas were drained after 1960, and by 1991 farmland in the delta exceeded 100,000 hectares, with more than a third of its surface affected by crops, plantations or fish farms. Dams built upstream in the second half of the 20th century have left the delta short of sediment. To see where all that water starts, follow our Danube River guide upstream, or compare this delta with Europe’s largest, the Volga Delta on the Caspian, and with the sea it feeds, the Black Sea.