FLOW MODELLING OF TICINO-ADDA BASIN FOR PREDICTION OF GROUNDWATER LEVELS IN CLIMATE CHANGE SCENARIOS

Undergoing climate change could affect substantially water resources in a long term period, not only for an overall drop of them, but for a different distribution of their availability during the hydrological season. Particularly irrigation systems could suffer of that problem, since they need water in specified seasons (springsummer) when usually it has a depletion. Storage of groundwater in aquifers in cold and wetter seasons, when cultivations don't need irrigation, could be used in order to soften irrigation systems water deficit in warmer and drier ones. Regional groundwater models have a key role in the management of groundwater resources, not only evaluating resource availability nowadays, but also predicting effects of management measures in different scenarios. The hydrogeological conceptual model of Ticino-Adda groundwater basin (having an extension of about 8000 km2 between Ticino and Adda river) was implemented based on a revision of the previous study on aquifers of the Lombardy region, conducted by ENI and Regione Lombardia. 87 hydrogeological cross-sections were used to build the bottom of the first 3 aquifers of the groundwater basin (Group Aquifer A, B and C) by means of a detailed database of hydrostratigraphic logs (about 15 thousands in the whole basin) from ARPA Lombardia. The conceptual model was the starting point for the implementation of a basin scale groundwater flow model (MODFLOW), whose steady-state calibration was performed by means of groundwater survey data conducted by Lombardy Region in May 2014 in 440 observation points in the 3 aquifers examined. Results of the calibration process point out a residual absolute mean scaled on observation range of about 4 %, suggesting a good accuracy. A pilot groundwater flow sub-model of about 255 km2 was then implemented in the north zone of Lodi Provincia, comprising a large part of the Consorzio Muzza Bassa Lodigiana irrigation district, in order to evaluate the quantity of groundwater resource in climate change and current climate scenarios. Using a down-scaled model (Quantile Mapping method) from the Regional Climate Model, predicted temperature and rainfall for the period 2071-2100 was obtained so that a transient model could be built to estimate change in groundwater resource availability. Furthermore, some analysis had made on the possible exploitation of the groundwater resource for the softening of irrigation deficit in the global warming scenario first implemented