As Portas reservoir keeps Camba river waters, which has its birthplace at the municipality of Laza, in San Mamede mountain range, at 1.480 meters in height. The course of the river is encased at its northern side by Queixa and Invernadoiro mountain ranges, and by Peña Nofre mountain range in the south. The flow managed by the dam makes use of hydroelectric power from Camba and Conso rivers, both tributaries of Bibei river, and this one, in turn, tributary of Sil river.
The reservoir was built in this gorge in 1974, over geological faults called “de los Romanos y Mateo”. With an area of 1.183 hectares, is a type of double curvature arch dam which is 141 meters high, being the one with the highest capacity throughout the Ourense Province with 538 million cubic meters. The land is formed by paleozoic siliceous slates with a great hardness, alternating with more clayey slates. The construction of this dam flooded the towns of Veiga de Camba, Campos and Cambalán.
Farmlands fertility surrounding the reservoir, as well as the landscape full of chestnuts, pines and heathland justify the presence of a varied and wide community of rabbits and hares, badgers, wolves, partridges, quails and wild boars. On the other hand fishing is allowed all year long and it has a great prominence in the reservoir, especially dedicated to cyprinids, black bass and trout.