Arborea, Oristano (Italy)
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Arborea is one of the most productive agricultural sites in Italy with a milk productivity among the highest in Europe.
In the past, it was an insalubrious swamp infested by mosquitoes bearing malaria disease. During the years 1920–1930, a huge land reclamation work was implemented for the entire plain: sand dunes were flattened and transformed into agricultural land and brackish and salted wetlands were drained by pumping water from below the sea level. A fertile plane was then generated consisting of rectangulare fields (2 to 4 ha) delimited and protected by eucalyptus edges and surrounded by a drainage network consisting of main channels and a dense network of smaller drainage channels.
Nowadays, Arborea is equipped with a modern system of agro-zootechnical companies, cooperative processing industries, an advanced system of associated services and a diversified range of activities that make it one of the more advanced areas of Sardinia.The farmers’ cooperative includes more than 200 farms managing some 30,000 dairy cattle on a 6,000-ha irrigated plain.
The intensive dairy cattle system, characterized by high levels of nutrients input (in particular N and P), if it is, on the one hand, the main driver of soil fertility, it is, on the other hand, the main cause of groundwater pollution considering the high concentration of nitrates and the eutrophication caused by phosphorus in the surrounding wetlands and lagoons. Thus, since 2005, Arborea has been recognized as a Nitrate Vulnerable Zone.
In the plain, the MENAWARA action consists in the implementation of a Forested Infiltration Area (FIA) system over a surface of around 0.7 ha by using drainage water, which usually flows to wetlands, to recharge the sandy phreatic aquifer (SHU) through a Managed Aquifer Recharge (MAR) technique, without compromising the minimum vital flow of the drainage network and wetlands.
👉The aim is to test the FIA technique as best practice which could be integrated by the Regional Agency of the Hydrographic District (ADIS) into the Sardinia Basin Management Plan as a possible tool to mitigate the quantitative-qualitative degradation of groundwater not only in the Arborea plain but also in similar hydrogeological context.
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Managed Aquifer recharge (MAR) is an increasingly worldwide important water management strategy to mainatin, enhance and secure stressed groundwater systems and to improve water quality.
FIA is a MAR technique consisting in the distribution of surface water on areas specially equipped with a network of drainage trenches and forested with trees and/or shrub species. The forest area maximizes the infiltration rate whereas the “active layer” generated in the rhizosphere has an effective action to promote nitrate attenuation, due to the occurrence of anoxic conditions, abundant organic matter provided by the woody plants and denitrifying bacteria living in symbiosis with the roots.
In collaboration with the Arborea Farmers’ Cooperative and the Oristanese Land Reclamation Consortium, a pilot site has been identified in the southern part of the Arborea plain, where high nitrate concentrations in groundwater, even over 250 mg L-1, have been detected.
The FIA System consists of 6 parallel recharge trenches with a depth of 1 m which are supplied with drainage water, pumped from an existing dewatering pumping station. Water infiltrates into the sandy soil through the trenches towards the aquifer. An incoming sediment control system (a mesh filter) has been installed upstream to the system.
In the recharge trenches, rows of poplar (white and Luisa Avanza species) and euchalyptus trees have been planted thanks to the support of students from the Agricultural Technical Institute of Bosa. In such forest areas, the water that infiltrates into the soil meets an effective filter made up of tree roots.
While waiting for the full development of the forested area that, in the medium-long term, will ensure the denitrification process, the depurative action, in the short term, is ensured by an innovative Passive Treatment installed on the bottom of the recharge trenches. The system consists of a mixture of inert and organic materials, to attenuate organic and inorganic contamintation and to prevent clogging processes.
A monitoring system has been installed to assess the groundwater quality after the recharge and the impacts on the phreatic sandy aquifer.
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NRD UNISS has been working since several years in both exploring with stakeholders a range of options to mitigate the N surplus in the Arborea plain, in facilitating dialogue and in collaborating for systemic change and local economic growth. The participatory and knowledge-sharing approach (living lab) has been adopted also in MENAWARA through meetings and public events that gathered together the main stakeholders of Arborea and Oristano province including social, economic and institutional players laying the foundations for a sustainable learning space.
Synergies with current ENI CBC MED standard project "MEDISS" and PRIMA project "SUSTAIN COAST" allowed the creation of a fervent and rich environment where the greatest number of actors possible could exchange experiences and discuss possible solutions.
