Hydrochemical and isotopic groundwater investigation in the Oltrepo region (Po Valley, Northern Italy)

A hydrogeologic investigation was conducted using hydrochemistry and isotope techniques in the lowland of the Oltrepò region (Po valley, Northern Italy). Groundwater generally displays a calcium bicarbonate facies. Along major discontinuities, the Po valley brines moves upward and mix with fresh groundwater. Stable isotopes of the water molecule indicate the main aquifer recharge areas, corresponding to the alluvial fans of the major rivers flowing from the Apennine towards the Po river. The observed different deuterium excess in groundwater relates to the origin of precipitation and the location of the river drainage basins. A hydraulic connection, underneath the Po river, between the deep aquifers of the Lomellina and the Oltrepò is also evidenced, implying that deep groundwater is recharged in the pre-alpine area and is several thousand years old.