Elvo
The Elvo (Piedmontese: "Elv") is a torrent (an intermittent stream) in the Piedmont region of north-west Italy and is the principal tributary of the Cervo. It runs through the communes of Sordevolo, Occhieppo Superiore, Occhieppo Inferiore, Cerrione and Salussola in the Province of Biella, and of Carisio and Casanova Elvo in the Province of Vercelli. The river’s valley is named after it as the Valle dell'Elvo. Here the municipalities are organized into two comunità montane: the Comunità Montana Alta Valle Elvo in the upper part of the valley, and the Comunità Montana Bassa Valle Elvo in the  lower. Many of the water courses of the Canavese and of the area of Biella—the torrent Orco, for example—are noted for the presence of gold-bearing sands. In the case of the Orco these are concentrated in the area of the Bessa nature reserve. Course. The river’s source is at an elevation of about on the slopes of Monte Mars, in the heart of the Biellese Prealps. Having passed through various centres of population, it is joined from the right at Mongrando by its major tributary, the Viona. From here its broad pebbly shores follow the edge  of the Bessa nature reserve, which lies to its right and is part of the Riserva naturale orientata delle Baragge. Near Salussola it enters into the plains of Vercelli and follows a slower and more sinuous course before emptying into the Cervo near Quinto Vercellese. Regime. The Elvo has a regime typical of a prealpine Italian torrent with maximum discharges in the autumn and spring together with a tendency to dry up in the summer and winter months. In the event of high levels of precipitation it is liable to become ‘torrential’.