The area of Fontana Gigante is situated in the lower plain of Vercelli. The site is characterized by the presence of a lake basin formed by eight adjacent water stretches, with a variable size and covering a total area of about 12 ha; the water level goes from 10 to 180 cm. Their origin is linked to the drainage of natural aquatic systems and the digging of basins used for hunting and sports fishing purposes, subsequently undergoing a naturalization process.
The site represents the second natural water system of the Province of Vercelli after Viverone Lake. The area seems like a semi-buried marsh, almost entirely covered with vegetation dominated by common reed formations and, in the marginal areas, by Salix cinerea marshy-shrubby formations. According to a classification of the local vegetation considering the level of naturality, rarity at a local and regional level, as well as the renaturalization potential, the most important coenoses as far as conservation is concerned are: water lily formations dominated by Nuphar luteum, pioneer common reed formations with Bidens cernua, ripe common reed formations with Thelypteris palustris, hygrophilous shrub formations dominated by Salix cinerea, hygrophilous alder formations, uncultivated wetlands, mesohygophilous shrub formations with Salix cinerea and Salix alba, mesophyte oak-alder formations, Quercus robur oak formations, hygrophilous oak woods with Quercus robur and Salix cinerea.
to now, 21 species of Odonata have been identified in the area: they
represent about the 50% of the species living in Piedmont. Several
species reproduce in the rice-fields and in the channels outside the
biotope and frequent the area only when they are adult. In any case,
the specific richness is relevant if we consider the limited area
covered by the biotope. Carabids are present with 57 species, some of
which are rather interesting for their rarity at a regional level and
their marginality with respect to the known distribution area (Platynus
krynickii, Europhilus thoreyi, Platysma gracile, P. oenotrium,
Acupalpus maculatus, A. luteatus, A. exiguus, A. flavicollis, Baudia
dilatata, B. peltata). Moreover, the area represents a shelter for a rich hygrophilous group of carabids.
As far as herpetofauna is concerned, 3 species of amphibians and 6 species of autochthonous reptiles have been signalled. The most interesting ones, since signalled in the rice-growing plain only in relict natural or semi-natural areas, are Bufo bufo, Anguis fragilis and Vipera aspis. Relevant is also the presence of Emys orbicularis, an extremely rare species in the region.
Moreover, in Fontana Gigante there are 11 bird species of European conservation interest, two priority at a national level (Bittern and Savi's Warbler), and 6 (3 certainly nesting: Bittern, Purple Heron, Savi's Warbler; 3 possibly nesting: Shoveler, Teal, Marsh Harrier) are of regional conservation interest.