Modello matematico di flusso nei sistemi acquiferi del Veneto Centrale

For the last thirty-five years, the aquifer system of Central Veneto (Italy) has been involved by an increasing demand of water for domestic and private use and by a relevant reduction of groundwater heads. The regional groundwater model developed is a large scale model taking origins from detailed studies of the hydrogeological system. Its purpose is to provide boundary conditions for the study of flow and transport models at smaller scale and to predict the behaviour of the aquifers in conditions different from the present-day ones (changes in rainfall trend, rivers regime, soil use). The three-dimensional flow model of the aquifer systems is based on a large number of experimental data, concerning both groundwater balance (measured rain in pluviometric stations, water flux dispersed by rivers and irrigation channels, water flux springing out of the springs, water withdrawal from a large number of private and public wells) and hydraulic permeability of aquifers. A three-dimensional geological model of the system has been created by means of geological sections and stratigraphies. The flow simulations are performed using a tetrahedral finite element code. The model is calibrated on the basis of real piezometric heads and is used to analyze the interaction between the unconfined aquifer, located in the northern part of the study area, and the multiaquifer system that originates in this area and proceeds towards the sea. The model simulates reasonably well the water flow aquifers system of Central Veneto and permits to simulate the effects of changes in withdrawal policies and/or boundary conditions relevant to the complex aquifer system. The model will allow the establishment of causal relationships between withdrawal of water (whatever the production layer, and the extracted flow rates) and the fluctuations of piezometric heads anywhere in the system. We have investigated the robustness of the model towards variations of the geological model and towards variations of the hydraulic permeability of aquifers and low permeability lenses. The implemented 3D flow model has allowed to improve the understanding of the regional groundwater system and of its hydrogeological properties. The model permits to predict the response of the system to overpumping, fluctuations in recharges, relevant land use changes, new public derivations: so it is deemed of central importance for the management of water resources in the area.