Evaluation and mapping of groundwater resources allocation key factors in northern apennines torbidites: the pilot study of the Montone watershed (Forlì-Cesena)

The Northern Apennines chain is located along the border between Emilia-Romagna to the north and Tuscany to the south; on both sides of the chain heavily anthropized plains (Padana Plain to the north) and valleys (intermountaine basins like Florence plain and Mugello to the south) have porous unconsolidated aquifers with a locally high exploitation and consequent undesired effects like subsidence, groundwater depletion and contamination. By the way, differently from Central and Southern Appennines with high occurrence of limestones and other permeable formations, Northern Apennines has not been considered for a long time a possible groundwater reservoir for exploitation or for integration-emergency purposes; the huge outcroppings of torbidites, with more or less regular alternance of sandstones and marlstones/siltstones, has been considered for a long time a reason to consider this chain as a dominantly “aquitard type” behaviour fractured medium. But, as a consequence of the Tunnelling of the new railway connection (TAV) between Florence and Bologna, the boring of the E 45 national road coonecting Rome and Ravenna and also of the derivation tunnel of the Ridracoli reservoir in the Romagna Apennines, huge groundwater outflows were locally registered, particularly originating from the Marnoso-Arenacea unit, the most widespread torbiditic formation in the Northern Apennines. High yield local aquifers, with high renewal rate, were identified; the coefficient of effective infiltration, with a high contribution of what has been termed “deep interflow”, attains locally value up to 0.3 (Canuti et alii, 2002). The Geological Survey of the Emilia-Romagna Region, with the scientific support of the Earth Sciences Department of the University of Ferrara, has financed a research project with the aim of defining a methodology to evaluate and map groundwater resources allocation factors in the Northern Apennines area and specifically in the Marnoso-Arenacea and analogous flysch units. The project has identified as pilot research experimental area the Montone watershed in the Romagna Apennines. The final goal of the project, taking into account the results coming out from the pilot study, is the definition of rules and a legenda for the hydrogeologic mapping of groundwater resources in Northern Apennines. The research began in 2002, is forecasted to last at least one year more and has been considering until now the upper sector of Montone watershed, immediately bordering the main appenninic divide. The presented paper is a short outline of the research approach and of the main results until now obtained.