The main rivers originate from the Spanish Meseta; these in the northern part of Portugal are mainly directed towards the O.-SO. (Minho, Duero, Mondego); in the center towards SW. (Tagus), in the south towards S. (Guadiana). With the exception of these, which are the major rivers, the others all have very short courses. A common feature of Portuguese rivers is the clear distinction between the mountain section, in which the river flows at the bottom of very narrow and deep gorges and is often interrupted by waterfalls, and the much more regular downstream course, characterized by wide river beds and mouths estuary. In this second part almost all the rivers are navigable, at least by large boats, while the upstream section lends itself very well to the exploitation of hydroelectric energy, which is still very little used. Overall, they almost all have an irregular regime and derive their food mostly from the rains, with the greatest flow of water in autumn and spring and the least during the summer. In southern Portugal, where the rains are very scarce, the rivers in the summer period are reduced to a weak stream that flows between the gravel and sand that covers the river bed; the “fiumara” character of these rivers is very pronounced, especially in the areas where schists predominate.
The Minho, the great river of Galicia (length 280 km, surface area of the basin 22,500 sq km), separates Portugal from Spain for 75 km. This river, flowing in a very deep valley, has a torrential character up to Monção, from here instead its course becomes calm and is navigable up to the mouth. For Portugal geography, please check franciscogardening.com.
The Lima (basin area 1145.39 sq km) flows into Portugal for 62 km. and flows into the Atlantic at Viana do Castelo; it is a small river used mainly for motive power. The course, which is torrential up to Ponte da Barra, then widens into a sinuous valley often flooding the surrounding plains, which are transformed into natural grasslands.
In northern Portugal, the most important river from an economic point of view is the Duero (see), whose valley is the main communication route between the sea and the Traz os Montes region; it also constitutes one of the largest hydroelectric energy reserves and a large part of the economic life of the region it crosses (Paiz do Vinho) is linked to it.
Entirely Portuguese river is the Vouga (surface of the basin 3656.24 kmq., Length 136 km.), Which originates from the Serra da Lapa; with its course it separates the Serra Gralheira from the Serra de Caramulo and flows into the Aveiro lagoon. The Mondego (basin surface 6772, 29 sq km, length 220 km) originates from Serra da Estrella, which flows between picturesque gorges in the upper course and then, starting from Foz do Dão, becomes navigable (85 km). The Mondego waters are abundant and subject to frequent flooding.
The largest Portuguese river is the Tagus (v.; in port. Tejo), which constitutes a magnificent natural way of communication from the ocean to the border with Spain. Finally, the rivers of the Algarve, with the exception of the Guadiana, are nothing more than short streams, some of which end in estuaries more or less encumbered with sand. The Guadiana (v.) Flows in Portugal for 260 km. and in two sections it serves as the border with Spain: in N. between the Alemtejo and Extremadura, in S. between the Algarve and Andalusia.
Portugal has some lakes of glacial origin in the Serra da Estrella and coastal lagoons, of which the most important are those of Aveiro and Setúbal, which give a considerable quantity of salt.
Fauna, flora and vegetation. – The fauna of Portugal does not differ substantially from that of the rest of the Iberian Peninsula.
The phytogeography of Portugal is quite well known for the studies of M. Willkomm, J. Henriques, J. Daveau and others. According to Willkomm we can distinguish a north-Atlantic, a central and a south-Atlantic district; but perhaps it is better to take the Tagus as the dividing limit and distinguish the territory at the N. of this river from that at the S. and examine the different zones: littoral, plains and hills, mountain and subalpine.
The littoral zone has many northern species; there is the domain of the Pinus pinaster and the Armeria of the sect. Macrostegia in its northern part, while in the south of disappearing species of the northern beaches of Europe and takes over the Pinus pinaster the Portugal pinea, first mixed with it, then alone; there are the Helianthemums of the Halimium section and the Armory of the section. Otostegia together with Iberian or endemic species, Ulex Welwitschianus and Willkommii, Stauracanthus aphyllus and spectabilis, the Nepa, etc. In its southernmost part or coast of the Algarve, Mediterranean, Iberian and Mauritanian species grow and endemism occurs in the great promontories (Capo da Roca, Espichel, S. Vincenzo) which, pushing into the ocean, form an almost insular environment.
The area of the plains and hills includes all the lowlands, close to the coast, which are subjected to the action of the Atlantic climate and the elevations not exceeding 400-500 m. with their western sides. At No. associate the Portugal pinaster and the Quercus pedunculata ; on the edge of the mountain area is the Q. the Rhododendron baeticum is squat and along some watercourses. In the center we are associated with the Portugal pinaster, the Quercus lusitanica and the olive tree; Instead dell’Alemtejo in the western area there is the Portugal pinea alone or with Portugal pinaster ; the shrubby vegetation is formed by Quercus coccifera, Q. humilis, Ulex, Nepa, Stauracanthus, Helianthemum frutescenti, Chamaerops humilis, while in the eastern Alemtejo pines are missing, Quercus ilex and Q dominate. suber and among the shrubs the Cistus ladaniferus, and in the humid areas grow the Nerium oleander and the Securinega buxifolia. South of this area are Q. ilex, Nepa, carob, and in the sub-mountain Q. Mirbeckii, Castanea vesca, Rhododendron baeticum, Myrica faya.
In the mountain area we can distinguish a cismontana part subject to sea winds and a transmontane part sheltered from these winds, whose flora differ considerably from each other.
The subalpine zone formed by the highest peaks of the territory, which do not exceed 2000 msm (for which there is no alpine zone): here is the Juniperus nana and the Nardus stricta in dense and compact tufts, in the north there are formations of Ericaceae replaced in the south by spots of Cistus.
Orange thrives throughout the low coastal area, penetrating the valleys of the Tagus and Duero; the date palm is found only in southern Portugal and the Macrochloa tenacissima esparto is found only in the Algarve.