Danube Delta: A lost paradise

The Danube Delta begins at the first ramification of the branches called the Ismail Ceatal. It is included in the lobate type among Terra's deltas, and far as dimensions are concerned, it is on the 24th position. The approximately 300 tributary streams ensure, when flowing into the delta, a medium multiannual flow of 6430 cubic meters/sec. The maximum flow was recorded in 1897 when it reached 1900 cubic meters/ sec, and the minimal flow was 1280 cubic meters/sec., recorded in 1942. The conditions of the levels, when entering the delta, display a polyphase behavior, with repeated rising and diminution in cycles, with amplitudes and durations which vary from year to year. The quasypermanent fluctuations of the water level demand the typical hydrological note of the delta. The most frequent highest levels are recorded in spring and in early summer, and the most frequent lowest levels are recorded in autumn and winter. The hydrographic network is represented by the Chilia, Tulcea, Sulina and The Sfantu Gheorghe branch borders the ancient relief of the Tulcea hills

The Sfantu Gheorghe branch borders the ancient relief of the Tulcea hills

Sfantu Gheorghe branches, and by the channels, streams and sahales among these, with a total length of 3500 km.
The Chilia branch begins at M.34 where the Ismail Islet is located and it is 121 km long up to the river's mouth of the Stambulul Vechi (the Old Istambul) branch from the Chilia secondary delta. The branch ensures at present the flowing of 55% of the total flow of the Danube at the top of the delta. The specific character of the branch is entailed by the two diffluences; the first is between Pardina (the 76 km) and Chilia Veche (the 46 km), and the second one between the 38 km and Periprava (the 22 km). These ramifications with the isles between them represent old secondary deltas of the Chilia branch. Downstream Vilcov there is at the top of the secondary delta Chilia, which began to form at the end of the XVIII-th century, coming nowadays to reach an area of 400 km2 with a medium rising rhythm of 1.8 km2 per year. Most of the Chilia secondary delta surface is to be found on the Ukrainian territory.
The Tulcea branch begins at M.34 (the Ismail Islet); it is only 17 km long and- at present it ensures flowing of 45% of the total discharge of the Danube. Between M.41 and M.37, it forms a meander curl, which culminates in Tulcea, where it has maximum depth (38m).
The Sulina branch begins at the Sfantu Gheorghe Islet that is to be found at M.34. Initially, it was winding and shallow. The Sulina branch was revamped for navigation by dredging starting with 1857 and, from 1868 by cutting the curls of the meanders. The revampings were finished in 1902, when the Sulina branch was made shorter with 21 km., being completely retrofitted and transformed into a shipping canal for oceanic ships. These refurbishments have been the first anthropic interventions with major effects in the transformation of the structure and of the deltaic system functions. At present, it transports approximately 22% of Tulcea's branch total flow. Downstream Sulina advances into the sea almost 8 km. At the mouth of the canal, sandy and clay deposits are accumulated. They're forming a bar that needs to be constantly dragged in order to ensure a minimum depth of 11 m necessary to allow access for sea ships.
The Sfantu Gheorghe branch begins at the islet with the same name (M.34), its total length is 110 km and it transports about 23% of the Tulcea's branch flow. It does not display diffluences. Downstream the 85 km, it is the largely winding forming 7 meanders curls, the biggest varying between the 85 km and the 64 km, known as the Murighiol meander. Between 1983 and 1985 these meanders were cut in order to shorten the navigable rout. The branch finishes off with a small secondary delta whose area is 13 km2 at present. The delta began its formation process at the beginning of the last century, developing with the medium multiannual rhythm of 0.07 km2 per year. The secondary delta, Sfantu Gheorghe is blocked by the barrier island Sacalin.
Sahales are old branches of the Danube that were left inside the delta. They are properly represented on Vidrascu's map, dating from the beginning of the century, later on being transformed in to canals by dredging and rectification. The Sireasa, Sontea, Papadia,Iacob, Adinca, Pardina, Repedea, Gotca, Poliacova, Bratusca, Statului sahales used to be between the Chilia and Sulina branches. Of all these only Sontea and the last tree above still exist, the others being completely transformed or having disappeared as a result of damming and draining. Between the Sulina and Sfantu Gheorghe branches there were two big sahales, Litcov and Macovei, both being revamped through hydrotechnical workings.
Garle are natural link arteries between branches and the stagnant aquatoriums inside the delta. Between the Sulina and the Sfantu Gheorghe branches, the Eracle, the Lopatna, the Matita, the Sulimanca, the Magearu streams are maintained. Between Sulina and Sfantu Gheorghe there are the Perevolovca, the Vatafu, the Busurca, the Imputita streams, and south of Sfantu Gheorghe branch there were the Dunovat, the Dranov and the Cernet, revamped under the guidance of Gr. Antipa, as early as the beginning of the century. Most of the streams are clogged up or rectified.
Stagnant aquatoriumsare ghioluri, pools, backwaters,lakes, lagoons. Ghioluri are deltaic lakes with great areas and depths, which are undergoing different stages of clogging at present. The main marshes are Fortuna, Matita, Babina, Marhei, Obretin (between the Chilia and Sulina branches) Gorgova, Isac, Puiulet, Puiu, Lumina, Rosu (between Sulina and Sfantu Gheorghe) and Dranov (south of Sfantu Gheorghe). Pools have reduced areas and depths, many of them having been formed by the mineral and biogen clogging of marshes. North of the Sulina branch the most important pools are: Tataru, Mester, Papadia,Nebunu, Baclanesti, Babinti, Rosca, Buhaiova, and south of Sulina there are the following pools: Iacub, Cuibida, Pojarnic, Rosulet, Uzlina. Japses are pools found in highly advanced stages of clogging, especialy biogen clogging. In summer, backwaters are invaded by submerged and floating vegetation, which makes them look like swamps.
In shallow waters they dry up. Lakes are prolonged and narrow, formed through the blocking of the little deltaic gulfs by sandy barriers in ascending evolution. When deltaic barriers reach the stage of descending evolution, lakes are open, first by wickets which gradually become larger. This is how Zatonul Mare and Zatonul Mic, in the south of the delta, were formed. Lagoons are wide aquatoriums formed through the blocking of the Dobrudja gulfs by series of sandy barriers. Razelm is the biggest lagoon, Sinoe (115 km2), Golovita (85km2) and Zmeica (60 km2) come after. Lagoons are supplied with waters coming from the Sfantu Georghe branch through the Dunovat and Dranov canals. Soth of Razelm lagoon there are the little lagoons in the Peritesca Leahova complex.
The conections between the flowing and the stagnant aquatoriums are established depending on the polyphase conditions of the lowing waters on the Danube. In spring, as the rivers's flows grow, turbid waters loaded with alluvial deposits and nutrientsget through the channels, streams and sahales inside the delta supplying the marshes, pools and backwaters. This is the filling up interval which frequently lasts by the end of May and during this period a volume of maximum 5 thousand million cubic meter of water may accumulate in the delta. There follows the stagnation interval of waters into the delta when a process of alluvial deposits decantation takes place, yearly about 1 million tones of sendiments deposit into the delta. The greater the flows that entered the top of the delta, the longer the stagnation interval. The decreas of the flows specific to the late summer and autumn determines the decrease of the flows on branches and simultaneously the release of the emptying interval of the delta. Waters flow through streams and channels, at confluence with branches of the river, the difference between the turbid waters and the clear waters from the delta being obvious. Owing to the frequent fluctuations of the flows on the Danube, during one year, several cycles of filling up stagnation-emptying may develop.