Danube Delta Biosphere Reserve - Romania

During the period 1921-1990, the average annual water discharge was 6,570 m3/s-1 with a mean variation range of about 5,700 m3/s-1 at the delta entrance. The extreme values were recorded in June 1970 at 15,440 m3/s-1 and in 1954 at 1,610 m3/s-1.The highest values quoted in the literature are 17,700 m3/s-1 in 1958 or even 35,000 m3/s-1 in 1897. The hydrographic network plays an important role in the appearance,evolution and functioning of the delta system. The main branches and the secondary streams have evolved over time, depending on the neotectonic factors and intensity of the silting processes.According to the most recent measurements (P. Gastescu and Driga,1983) the total length of the natural (or partially modified) streams is about 1,743 km and that of the canals is about 1,753 km.The lakes represent another important morpho-hydrographic feature of the DDBR(Danube Delta Biosphere reserve)landscape. A recent inventory of the lakes within the delta has revealed that before 1980 there were 668 lakes with a total area of 31,262 ha (9.28% of the delta area). Because of the embankment and drainage of the Pardina and Sireasa agricultural polders the number of lakes was reduced to 479 and the area to 25,794 ha (8.06% of the delta area).