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In this study, modelled groundwater actual flow times in intermediate and deep aquifers, covered by regional scale impermeable aquitards, were compared with 4He and 81Kr age dating results. To improve the reliability of the steady state 3D groundwater flow model, the isotopic ages of deep groundwater were compared to the MODPATH modelled travel times. The highest helium values in groundwater reservoirs coincide with fault zones in the crystalline basement and sedimentary cover near Rapakivi granite massifs. Insights into isotope-geochemical anomalies of the Baltic Artesian Basin intermediate and deep groundwater support their main distribution peculiarities in the flow path towards the Baltic Sea coast lowland and seabed depression as the regional groundwater discharge area.

Groundwater abstraction not only affects subsurface water, but also causes changes in the hydrosphere, lithosphere, and biosphere. There are certain symptoms of these environmental changes that might be designated as geoindicators. Geoindicators related to groundwater abstraction and contamination in Lithuania have been classified into three groups related to: (1) the decline/rise of groundwater levels, (2) the deterioration of groundwater quality, and (3) the intensification of water-rock interaction. On the basis of hydrogeological and hydrological investigations carried out over many years, different environmental impacts of intensive groundwater use are demonstrated. The most important among them are the formation of depression cones, intensification of groundwater pollution, saltwater encroachment, and the intensification of karst.

Pietų Lietuvoje esantis cenomanio-apatinės kreidos vandeningasis sluoksnis pasižymi savitomis plačiai paplitusiomis sūraus požeminio vandens anomalijomis. Šis sluoksnis formuojasi vandeniui pertekant per gilumines lūžių zonas iš giliau slūgstančių triaso ir permo vandeningųjų sluoksnių. Sūraus vandens intruzijos išreikštos didesnės chloridų koncentracijos kupolais, aptinkamos iškrovos vietose – Šešupės ir Nemuno upių slėniuose, dažnai siekia net gruntinio vandens sluoksnius. Sūraus vandens kontūras juda link vandenviečių, blogina požeminio vandens eksploatacinių išteklių kokybę ir riboja jų kiekį.

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