HR: 1340h
AN: H33H-1715    [Abstracts]
TI: 3-D Numerical Modeling as a Tool for Managing Mineral Water Extraction from a Complex Groundwater Basin in Italy
AU: * Zanini, A
EM: andrea.zanini@unipr.it
AF: Università degli Studi di Parma, Viale G. P. Usberti 181/a, Parma, PR 43100, Italy
AU: Tanda, M
EM: mariagiovanna.tanda@unipr.it
AF: Università degli Studi di Parma, Viale G. P. Usberti 181/a, Parma, PR 43100, Italy
AB: The groundwater in Italy plays an important role as drinking water; in fact it covers about the 30% of the national demand (70% in Northern Italy). The mineral water distribution in Italy is an important business with an increasing demand from abroad countries. The mineral water Companies have a great interest in order to increase the water extraction, but for the delicate and complex geology of the subsoil, where such very high quality waters are contained, a particular attention must be paid in order to avoid an excessive lowering of the groundwater reservoirs or great changes in the groundwater flow directions. A big water Company asked our University to set up a numerical model of the groundwater basin, in order to obtain a useful tool which allows to evaluate the strength of the aquifer and to design new extraction wells. The study area is located along Appennini Mountains and it covers a surface of about 18 km²; the topography ranges from 200 to 600 m a.s.l.. In ancient times only a spring with naturally sparkling water was known in the area, but at present the mineral water is extracted from deep pumping wells. The area is characterized by a very complex geology: the subsoil structure is described by a sequence of layers of silt-clay, marl-clay, travertine and alluvial deposit. Different groundwater layers are present and the one with best quality flows in the travertine layer; the natural flow rate seems to be not subjected to seasonal variations. The water age analysis revealed a very old water which means that the mineral aquifers are not directly connected with the meteoric recharge. The Geologists of the Company suggest that the water supply of the mineral aquifers comes from a carbonated unit located in the deep layers of the mountains bordering the spring area. The valley is crossed by a river that does not present connections to the mineral aquifers. Inside the area there are about 30 pumping wells that extract water at different depths. We built a 3-D numerical model of the study area using a finite difference grid describing the surface with 20000 cells (each cell is 30m × 31m). 17 layers represent with high accuracy the boreholes stratigraphy and the available geological cross-sections of the area. The aquifer is described using 6 materials characterized by different hydraulic parameters. Taking into account the particular morphology and the boundary conditions, only 30% of the grid cells were activated in order to improve a better simulation of the physical domain obtaining the reduction of the computation nodes and the speeding up of the numerical processes. MODFLOW 2000 was used to solve the flow problem. After assigning the boundary conditions as fixed heads downstream and input flow discharge upstream, a first calibration of the model has been carried on in steady state condition on the basis of the piezometric heads collected during a measuring campaign. Only a few hydraulic conductivity values were available, so the calibration consisted in varying the hydraulic conductivity of the materials with the aim at reproducing the measured heads in the monitoring points. A refined second calibration in dynamic condition has been carried on because a large dataset of observations during the wells activity were available. The result of the work was a model that allows the study of the flow directions in the aquifers and the analysis of different scenarios of increasing extraction of mineral water with new drilling of pumping wells.
DE: 1829 Groundwater hydrology
DE: 1876 Water budgets
DE: 1880 Water management (6334)
DE: 1894 Instruments and techniques: modeling
SC: Hydrology [H]
MN: 2007 Fall Meeting