Danube Delta

Short historical view

The first to notice the deltoid shape of this system was probably, Herodotus studying the Nile Delta nearly 2,500 years ago. His “Histories” provide the first information of the Danube (Istros) and its delta. Since ancient times the Danube Delta has been an object of interest to European people.

Hypsometry

The Danube Delta is a very low flat plain, lying 0.5m above Mean Black Sea Level with a general gradient of 0.006m/km. The highest point o the delta is given by the sand dunes in Letea (+12.4m) and the maximum depth is on Chilia arm (-39 m).

Hydrographic network

According to the most recent measurements the total length of the natural streams is 1,743 km and that of the channels is about 1,753km.

Lakes

There are 479 lakes in the Delta. In the western part of the delta where the siltation is more intense, the lakes are more numerous, small and shallow (

The Razim-Sinoe lagoon complex is the largest lacustrine area of Romania covering 101,500ha. It was formed by closing off the old marine gulf of Halmyris and now is separated by the Black Sea only by a narrow beach ridge. The depth of these lakes ranges between 1.0m and 3.5m.

Hydrology

During the period 1921-1990 the average annual water discharge was 6,570 cubic meters/sec at the delta entrance; the extreme value of 17,700 cubic meters/sec was recorded in 1958. The average annual suspended sediment discharge was 29.2 million tons in the period 1981-1990. In the delta the amount of incoming sediment/year is about 1,5 million tons, a large part of which is deposited in secondary streams, canals and lakes.

Climate

The Danube Delta has a continental-temperate climate with some pontic (marine) influence. The average number of hour sunshine is about 2,500 hours/year.

Average annual air temperature is 11 degrees Celsius with a minimum average in winter of -1.5 C (January) and max average in summer 22.7 C (July).

Absolute minimum air temperature – 27.2 C (18.01.1963)

Absolute maximum air temperature – 39.7 C (02.08.1945)

Precipitation is influenced by the north Dobrogean tableland and by the Black Sea. The average precipitation is 438.4 mm in Tulcea and 330.5 mm at Sulina.

The snow starts to fall in the second week of December until the middle of March.

The air humidity of about 80%, is the highest in Romania, and increases towards the east: 80% at Tulcea and 86% at Sulina. In wintertime air humidity in Sulina may reach up to 90%.

The number of cloudless days is 66 in Tulcea and 80 at Sfintu Gheorghe.

The potential evapotranspiration is > 700 mm/year. The Danube Delta has one of the highest atmospheric moisture deficits in Romania (- 300 – 400 mm).

Aeolian condition – Winds blow 80% of the year and with almost the same frequency from all directions. However, the prevailing direction is from the northwest, followed by the north wind. The highest speed winds – 8.4 m/s -were recorded near the sea.

Human settlements

The first signs of human settlements discovered in the delta date from before the Middle Ages, and even go as far back as the Neolithic Age. The ruins of the ancient Greek cities of Histria and Argamum bear witness this fact and lie on the western side of the present day Razim Sinoe lagoon complex, they were built in the 6th- 5th centuries BC. Constantine VII the Porphyrogenitus (950) mentions the present town of Sulina by the name of Sollina. During the Turkish Empire, which started at the beginning of 15th century, some new settlements where established – Caraorman (1819). The most recent settlement in the Danube Delta is Maliuc in 1953.

Population

In the 20th century the population of the Danube Delta fluctuated between 15,000 and 21,000 inhabitants, being strongly influenced by the two world wars and the development of the town of Tulcea. The population of 15,590 recorded in 1992 was the lowest population for

(Ecosystems of the Romanian Danube Delta Biosphere Reserve – Danube Delta Institute)