Spain Hydrography

Five distinct coastal stretches correspond on the two seas to the Iberian peninsular pentagon, and therefore also to the territory of Spain, of which two face Spain and the others each according to one of the cardinal points. The watershed between the Atlantic and the Mediterranean runs along the north-eastern edge of the plateau and the betic mountain range: more than half of that territory is therefore tributary to the former, but of the major rivers that fall on this side only one, the Guadalquivir, runs entirely within the political borders of Spain, flowing, together with the Guadiana, to the sea front of SO. On the other fronts loom, more or less imminent, the mountain rims of the mesetaor peripheral reliefs: therefore there is no space for the development of significant hydrographic basins. The only exception, with the Guadalquivir, is the Ebro, which conveys the waters of the Aragonese depression, but is forced to open its way through the mountain diaphragms that block its path near the mouth. The Ebro is also the only one of the great Spanish rivers that turns to E., in contrast to the prevailing inclination that determines the course of the others. In spite of the abundant liquid inflow that comes from its northern flank (Pyrenees), the intense evaporation and the irrigation bloodletting (canals of Tauste and Imperiale) greatly reduce the liquid flow, with which the river struggles to dispose of its heavy flood load. The Guadalquivir has a completely different character, which just came out of the spring area, in Cordoba, has only a hundred m. high and is ascended from the mouth for 120 km. from the tidal wave. Its navigability is also related to its richness of waters, to which the regular toll of the Sierra Nevada, brought to it by the Genil, contributes in the first place.

According to, the other three major rivers – the Tagus, the Duero and the Guadiana – are characterized above all by an equilibrium profile that is still very irregular: exiting the mesetain which they rise and wander, embedded in deep riverbeds and interrupted by rapids, they must overcome with a series of waterfalls the abrupt difference in height that separates the plateau to the West from the coastal strip along the Atlantic; moreover, their flow is extremely variable, with rapid and disastrous floods, which alternate with long periods of low water, in which they often look more like streams than rivers. For this reason their anthropogeographical importance does not cease, but the most important uses of them, which enhances their hydroelectric reserves, does not exclusively concern Spain. All three rivers in fact cross the Portuguese territory.

As for the minor watercourses, they can on the whole share the characteristics of a still little evolved erosion cycle. Thus on the southern side of the Sierra Nevada, as on the Cantabrian coast, for example, the proximity of the base level, the abundance and regularity of the flows and the recent geological history determine a very intense denudation, with which these rivers evidently tend to a still distant equilibrium. The resulting copy of the sedimentations has a geographical importance in some areas that cannot be overlooked: thus, for example, the creation of the Levantine huertas is to be placed in relation with the alluvial materials that the rivers of the Mediterranean side have transported and carry from the meseta(Júcar, Segura), where with regressive erosion they managed to push their warheads, or from the raised edges of this (Guadalaviar, Mijares).

With all this, the differences between the different hydrographic dominions are very marked: if only between the regularity of outflow of the Cantabrian rivers, and the capricious behavior of those who head to the Levantine region, where disastrous floods can be determined in a short time creek beds that remain dry most of the year.

It should be noted the lack, throughout the Spanish territory, of real lakes, which is matched by the abundance of coastal lagoons (albuferas) and lagoons with variable perimeter (the maximum, that of Gallocanta, reaches 25 sq km in winter.) in arid areas with a steppe regime.

Also as regards its pedological conditions, the Spanish territory presents all the varieties recognizable in the peninsula. Basically, when one leaves aside the restricted Atlantic domain, of which brown lands and peaty soils are characteristic, three quarters of the country present the typical formations of arid and subarid areas: above all the Mediterranean red lands, within which they widen to mo of islands, in the two Castles, in Aragon and in Spain del Guadalquivir, the soils rich in alkaline-earthy salts belonging to the sectors with steppe facies. This behavior, as well as with the current climate, must, according to all reasonableness, be related to the conditions created from the Miocene onwards, following the predominance, or at least the widespread development, of continental deposits.podzol.

Spain Hydrography