The Danube Delta Biosphere Reserve is located in the eastern extremity of Romania (south-east, in Tulcea County and in the north of Constanta County), where the Danube’s mouths flows into the Black Sea. It comprises the Danube Delta, the Danube marshland, the river meadow up to Cotul Pisicii, the lagoon complex Razim-Sinoe and the Black Sea as far as 20 m in depth.
On land, the main point to all the reserve components is the city Tulcea, but one can enter the Danube Delta from the Black Sea, through Sulina, a small settlement placed on the seashore, where the middle Danube’s arm enter the Black Sea. The main access point to Razim-Sinoe lagoon complex is Jurilovca, where the southern side is opened through the locality of Vadu.
GEOLOGY AND GEOMORFOLOGY
There are four distinctive geo-morphologic units: the fluvial delta, the marine delta, the Danube Meadow and the lagoon complex. The three arms of the river and the network of channels, canals and lakes between them(here and there bounded by natural levees) made up the fluvial delta. The marine zone is characterized by sand dunes and sandy levees left by the river’s fresh water when flowing into the salt water of the sea, these levees being placed across the flowing direction. The most important levees are the following ones: Chilia, Ştipoc, Letea, Caraorman and Crasnicol. At the end of Sf. Gheorhge arm there is Sacalin Island, whose shape is continuously changed by the sea. The proper Danube Delta is a new unit, formed during the prehistoric era in a gulf, which was entirely silted up.
By the locality of Pătlăgeanca the river spills into two arms: Chilia(northward) and Tulcea(southward). The later one, very short, branches into another two arms: Sulina(71 km length) and Sf. Gheorghe(112 km length). Through Chlia arm about 60% of the river water flows into the sea, and the middle arm; Sulina is being rectified and dragged for the navigation. The three arms are linked by many secondary arms, channels, lakes and marshlands, many channels and lakes being navigable. Approximately 80% of the delta surface is covered by the water. In 80’s several ponds for fishery were set up but they have been abandoned meanwhile. Other areas have been converted to arable land.
The lagoon complex Razim-Sinoe is placed in the southern part of the reserve, gathering the former lagoons Razim, Sinoe, Zmeica and Goloviţa, transformed into freshwater or brackish lakes, ad they have been disconnected from the sea by a narrow sandbar. The old gates to th sea from Portiţa and Periboina have been closed in order to desalinate the lagoon water and make it suitable for irrigation.