The river Alva is born in Serra da Estrela at about 1600 meters of altitude, between Fraga das Penas and Curral do Martins. It runs for about 115 kilometres until it flows into the Mondego river, in the town of Porto de Raiva, near Penacova, after being broken by the Raiva Dam and the Aguieira Dam. Serving as an affluent, Alva integrates the Mondego river basin. It therefore borders the Mondego River to the north and west, the Mondego River to the south and southwest, the Ceira River, also an affluent of the Mondego River, and the Tagus River to the east and southeast. Along the way, excavated between the slopes of the Serra da Estrela and the Serra do Açor, there are several localities and some fluvial beaches, such as São Gião, Avô, Côja, Secarias or Caldas de São Paulo. The high variation of the flow is one of the main characteristics of this fluvial course. The precipitation, high in winter and low in summer, and the fact that it is largely controlled by the water system of the Serra da Estrela contribute to that variation.

Flora and fauna

On the slopes of the river Alva, there are scattered stands of maritime pine, eucalyptus and chestnut trees. Near the water courses, poplars, alder and willow trees predominate. In the waters of the Alva, the diversity of fish species is notorious, namely the barbel, the boga, the trout and the lamprey. In the humid places and near water lines we find the salamander and the Iberian frog, the heron, the river keeper and the otter. Among the vegetation, several species of birds can be seen, such as jay, blackbird and partridge. There is also room for foxes, rabbits and wild boars.

Geology

The river Alva sketched deep valleys and was determinant in the morphology of the relief, as well as for the human presence along the banks, which is noticeable in the weirs, wheels (azenhas) and canals.