On groundwater resources available in Oltenia Plain, Romania

The Oltenia Plain occupies ca 8,400 km² in the SW Romania. With decreasing altitudes from north to south, it includes three W-E elongated subunits: a High Plain (210-110 m elevation), followed to the south by the Danube Terraces (140-35 m) and by the large Danube Floodplain (40–25 m). The fresh groundwater resources are located in the Pliocene-Quaternary formations. The oldest Berbesti Formation consists of lacustrine sands (50-150 m thick) and is overlapped by the Jiu-Motru Formation composed of swampy clays and coal beds with sands insertions (150-300 m). The next lithostratigraphic unit, the Lower Member of the Danube Formation (15-20 m) was built during the Early Pleistocene. Finally, the Danube River moulded Valley own profile. As a result, the higher relief of the Oltenia Plain formed repeated down-cuttings of five-stepped terrace sequence and the Floodplain (Upper Member of the Danube Formation).
   The Berbesti Formation is a continuous multilayered aquifer, the hydraulic conductivity of 0.2-15 m/day and specific capacity values of 0.05-4.0 l/s/m.The Jiu-Motru Formation is the discontinuous multilayered aquifer (sands) on the mainly aquiclude clayey-coaly background. The specific capacity values of the lens-shaped tested sands are in the range of 0.01-0.25 l/s/m. The fine sands inserted on the aquiclude background are characterized by low Na⁺, K⁺, I⁺ contents and by higher contents of organic substances, CO₂, Fe³⁺, SO₂^4-, NO^2- and Br^-. The hydraulic conductivity determined through tests in situ has values between 0.1 and 5.0 m/day. The specific capacity has a large variation interval from 0.2 to 5.0 l/s/m.
   The Lower Member of the Danube Formation, represented by the alluvial fan, is discordantly disposed over the previous two formations and bears a continuous extended phreatic aquifer. Its potentiometric contour lines decrease from 200 m to the north to 95 m to the south. Despite the high hydraulic conductivity values (10-55 m/day), being situated at 40-60 m over the local base level of the floodplains, this aquifer discharges on the slopes of the main valleys and has limited resources.
   The six mono-layer aquifers bear in the Upper Member of the Danube Formation with 5 terraces and the floodplain of the big watercourses (Danube, Jiu and Olt). Within the Upper Member, there is a N-S increase of productivity (from 1-3 l/s/m in the N strip, to 3-6 l/s/m in the middle one and > 6 l/s/m within the whole Danube Floodplain.
   In the eastern subunit of the studied area – the so-called Leu-Rotunda Plain – the Danube Formation is covered by a continuous pile of the Aeolian Formation (30-35 m thick of loose wind-blown silts, clayey sands, fine to coarse sands, having like insertions fossil soils at different levels). Field investigations carried out during April 2010 in accordance to “Climate Change and Impact on Water Supply” Project (see logo) showed that the phreatic aquifer of the Aeolian Formation constitutes the historical source to feeding the people of 15 localities. In large areas, the depth of the water table ranges from 0.5 to 3 m, being vulnerable to estimated climate change. Its resource is contaminated by domestic seepage and fertilizers only within the perimeter of localities. There, the public fountains have around 1,200-2,100 μS/cm Electric