Lateral and induced recharge from Po river to paleo-channels in low Padana plain: the Settepolesini project (Ferrara)

Great rivers, like Po in the Padana plain, are a main water supply for municipal use; at the same time, however, surface waters are subjected to higher pollution risk, need expensive purification procedures and are exposed to recurrent episodes of drought in the season where higher is the demand for water supply. An interesting alternative resource may be identified in paleo-channels running near the river; such mainly sandy lithosomes are indirectly recharged by the big river and might become as well targets for the implementation of induced recharge project schemes. The paper deals with a sector of the “Po-shallow sandy aquifers complex”, located along the southern bank of the river across the boundaries of Lombardy and Emilia Romagna regions. The area is located 15 km to the west of the city of Ferrara, at the moment depending mainly on the Po river for its public water supply demand. In this area two different sandy aquifer occur, both in indirect recharge relationship with the Po: an upper unconfined Holocenic aquifer and a lower leaky confined Upper Pleistocenic aquifer, separated by a silty-clayey aquitard. Somewhere the two units amalgamate each other so originating a single unconfined high thickness aquifer; in this hydrogeological context it’s peculiar the presence of sand quarry lakes, so directly recharged by the Po. Water quality of this lakes is much better than that one of the Po itself due to the natural attenuation power of the porous medium. The paper shows the results of a groundwater heads and surface water stages continuous monitoring programme (active since July 2002), integrated by hydrochemical data, for studying the processes of pressure and mass transfert of this complex indirect recharge system, to evaluate the water budget of the Settepolesini lake and, trough a numerical modelling, the potential of stimulating induced recharge.