A Special Hydrogeological Unit – South Dobrogea, Romania

A Special Hydrogeological Unit – South Dobrogea, Romania

Geographically, South Dobrogea is situated at the intersection of the 44° north latitude with the 29° east meridian, its limits being: the valley of the Danube, in the west, the Black Sea, in the east, Topalu-Ovidiu fault in the north and the Bulgarian boundary in the south. In between these limits, the surface of South Dobrogea is of 5335 km². Geologically, the unit is made of a crystalline fundament belonging to the Moesian Platform, on which sedimentary-calcareous formations of Jurassic, Cretaceous, Precambrian and Sarmatian age lay, covered in loessoid Quaternary deposits. Altimetrically and morphologically, this unit varies between 100-200 m, its fragmentation being more accentuated towards the Danube and less marked towards the Black Sea. The presence of the calcareous stones in the subbasement leads to the presence an exo- and an endo-karst, which differentiate the drainage of the surface waters from that of the underground waters. The average annual temperatures of about 11° C and the precipitations of around 400 mm/year, along with the influence of the Eurasian anticyclones determine a slightly moderate semiarid continental climate towards the Danube and the Black Sea. From these morphological and climatic features, it results that the autochthonous hydrological potential is low, reducing and even annulling the alimentation of the underground aquiferous structures.

In contrast to these geographic conditions, the presence of certain significant underground water resources raises many questions concerning their source, their circulation and their physico-chemical characteristics. Following the investigations made using geophysical methods and drillings, it was noticed that the antequaternary underground waters gather in two complexes: a discontinuous Eocene-Sarmatian deposit, and a large Jurassic-Lower Cretaceous deposit, which contains significant water resources.  Qualitatively, the underground waters of South Dobrogea have potable and meso-thermal sulphurous characteristics.