Deuterium as natural tracer in groundwater from neighbouring area of Danube Delta Biosphere Reserve

Measurements of deuterium content of the groundwater from neighbouring area of Danube Delta Biosphere Reserve show that the waters are meteoric in origin, but at the same time the results showed that the water for three sampling points could not originate from local groundwater and have their recharge area at high altitude and a considerable distance. According to the delta D values the following categories of waters were delineated: (1) waters that belong to an confined aquifer in limestone and have their recharge in high altitude region, higher than 1000 m (delta D < - 80 parts per thousand); (2) waters tributary to the Danube river that have a small variability in time of delta D values (delta D > - 75 parts per thousand); (3) local infiltration waters, situated in the West of the investigated area towards the continental platform ed the Dobroudja, with high variability in time of delta D values, due to seasonal effect (delta D > - 70 parts per thousand); (4) waters originated in mixing processes between the waters with different isotopic content. The one endmember is heavier isotopic water that belongs to local recharged waters (local infiltration waters and waters tributary to Danube river) and the other endmember is the isotopically light water.