Along Mediterranean coastal areas, most of the industrial production, agriculture and population are concentrated. The consequent high demand for fresh water leads to groundwater overexploitation, pollution and eventually, saline intrusion. The Arborea plain, located in the central-western coast of Sardinia, is an intensive farming district based on dairy production and agricultural activities. The plain passed through deep reclamation actions in the 1920s, when the insalubrious swamp areas were covered, and a complex network of drainage channels and pumping stations were built to lower the piezometric level and intercept runoff waters. Since 2005 it has been declared a Nitrate Vulnerable Zone (ZVN -91/676/CEE) because of the high nitrate concentration measured in groundwaters and caused by manure and effluents (Biddau et al.,2018). According to the hydrogeological model of the coastal plain, a phreatic multi-layer aquifer is hosted within the Holocene littoral sands superimposed to a deeper alluvial aquifer hosted in Pleistocene continental deposits. The two aquifers are physically separated by a thick silty clay layer quite continuous northworth and are locally connected in the southern part of the plain because of the gradual thinning of clay deposits (Ghiglieri et al., 2016). To better understand the dynamics of the phreatic aquifer and to study the nitrate source and fate, a steady state and a transient numerical groundwater model have been implemented for the Arborea plain with Feflow 7.4, within the PRIMA-Sustain COAST project. In detail, the main water inputs (precipitation, irrigation), industrial and agricultural abstractions, and exchanges with surface waters, including the drainage channels, have been modelled. Lastly, various nitrate contamination and groundwater management scenarios were simulated. Preliminary results indicate that approximately 58% of the total annual outflow is drained by the ditches, while transport simulations globally underestimate the observed nitrate concentrations. A second groundwater model, now under development at the local scale, wants to simulate the efficiency of a Managed Aquifer Recharge system (MAR) implemented through a Forested Infiltration Area (FIA). The FIA pilot site has been realized in the south part of the plain by the NRD-UNISS of Sassari University in the framework of the ENI-CBC MED MENAWARA project with the objective of testing new strategies to mitigate the nitrate contamination of the phreatic aquifer.
3D Hydrogeological Numerical Modelling for the Sustainable Management of Groundwater in the Arborea Coastal Plain (Sardinia, Italy)
Antonio Maria Sessini
;Alberto Carletti;Claudio Arras;Stefania Da Pelo
2023-01-01
Abstract
Along Mediterranean coastal areas, most of the industrial production, agriculture and population are concentrated. The consequent high demand for fresh water leads to groundwater overexploitation, pollution and eventually, saline intrusion. The Arborea plain, located in the central-western coast of Sardinia, is an intensive farming district based on dairy production and agricultural activities. The plain passed through deep reclamation actions in the 1920s, when the insalubrious swamp areas were covered, and a complex network of drainage channels and pumping stations were built to lower the piezometric level and intercept runoff waters. Since 2005 it has been declared a Nitrate Vulnerable Zone (ZVN -91/676/CEE) because of the high nitrate concentration measured in groundwaters and caused by manure and effluents (Biddau et al.,2018). According to the hydrogeological model of the coastal plain, a phreatic multi-layer aquifer is hosted within the Holocene littoral sands superimposed to a deeper alluvial aquifer hosted in Pleistocene continental deposits. The two aquifers are physically separated by a thick silty clay layer quite continuous northworth and are locally connected in the southern part of the plain because of the gradual thinning of clay deposits (Ghiglieri et al., 2016). To better understand the dynamics of the phreatic aquifer and to study the nitrate source and fate, a steady state and a transient numerical groundwater model have been implemented for the Arborea plain with Feflow 7.4, within the PRIMA-Sustain COAST project. In detail, the main water inputs (precipitation, irrigation), industrial and agricultural abstractions, and exchanges with surface waters, including the drainage channels, have been modelled. Lastly, various nitrate contamination and groundwater management scenarios were simulated. Preliminary results indicate that approximately 58% of the total annual outflow is drained by the ditches, while transport simulations globally underestimate the observed nitrate concentrations. A second groundwater model, now under development at the local scale, wants to simulate the efficiency of a Managed Aquifer Recharge system (MAR) implemented through a Forested Infiltration Area (FIA). The FIA pilot site has been realized in the south part of the plain by the NRD-UNISS of Sassari University in the framework of the ENI-CBC MED MENAWARA project with the objective of testing new strategies to mitigate the nitrate contamination of the phreatic aquifer.
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