Water is an irreplaceable resource for the Ossola Valley, particulary if we speak about the most important river of this region: the Toce river. This blue vein passes along all the region, from north to south, for 82 km, from the Toce Falls (located in Frua, Formazza Valley), through the natural caves knowed as "Gorges of Uriezzo", to its mouth in Lake Maggiore.
Water is the largest modeller of the Ossola landscape and is also a vital commercial and economic resource for these lands.