The Virco stream, located in Bertiolo Commune, crosses the biggest survived alkaline fen. At the beginning of the ’80s it was enlarged and lowered to help the drainage of the surrounding areas, by removing an old mill lifting-gate that contributed to keep a sufficienthydraulic level for the fen.
The project, after the purchase of all fen estates, includes the original condition restoration of the Virco stream, by positioning height-suited thresholds on the bottom (with percussion-drive larch piling) and by narrowing the stream at alternate points to reduce its flow, to increase the sinuosity and to allow a new surrounding fen flooding.
Same actions are even scheduled for the Feret stream, in Gonars Commune.
The following actions are expected in the farmlands purchased through this project:
1) the ditch fill-in with made ground coming from environmental restoration works;
2) the drainage channels deep lowering in order to ensure the rain water removal;
3) the partial block of the final sections of drainage channels, with the ground level removal to help the water table raising.
In the natural areas (fens or wet meadows) purchased through this project there will be the wind-up of head/foot drainage channels or the splitting up of channels with more partitions, which prevents the water flowing.
These actions set a limit to water table drainage so as to allow, at the same time, the evacuation of rain waters that carry away nutrients harmful to the oligotrophic fen ecosystem.
For the conservation of the local flora and fauna it is quite essential to avoid the worst lowering peaks of water table and to limit theheight and temperature ranges that cause fatal effects to floristic and animal species.
The water table ranges attenuation will reduce even the actual eutrophication phenomena, due to organic material oxidation, with a consequent project target species habitat improvement.
With regard to the Feret irrigation ditch (Municipality of Gonars) no actions were carried out because it was devoid of water and totally covered by grasses due to refurbishment works made upstream on agricultural lands outside the Biotope.
With regard to the Virco irrigation ditch (Municipaloty of Bertiolo) the drawing of the project and the technical report writing has been longer than expected due to the heavy rainfall of the last two years and the need of repeated hydraulic measures of maximum and minimum flow rate (correct sizing of the works, hydraulic compliance, protection of adjacent private lands, maintenance of flow required by the actual derivations).
Collected data suggests that the ditch has usually a modest flow and is in large part - for more than 90% - supplied by fens. At discharge points of the adjacent ditches, the formed deposits will be settled with the planned works.
However it is already evident that the bottom of the ditch was naturally stabilized after the excavations carried out 20 or more years ago. The water level in the ditch, even in busy periods, it is always kept at least 50 cm below the level of the surrounding terrain.
With the completion of 5 threshold made of larch poles fixtures at the bottom of the ditch, the average slope of the bottom will remain the same and the total annual capacity will not be significantly altered thanks to the compensatory effect of the more constant supply of water to fens.
The result will be guaranteed in a decisive way thanks to the partial closure of the drainage channels among fens and the ditch, as expected from the project.
With this action, it will be also significantly to reduce the presence of sediments and organic fractions in the waters, improving their quality for use in fish nursery. The action will take place before the end of the project.