Vale do Guadiana (Guadiana Valley)
There are three types of landscapes that characterize Vale do Guadiana and attribute it peculiar features: the Alentejo peneplain, with altitudes below 200m and where extensive farming predominates; the quartzite elevations of the mountain ranges of Serra da Alcaria Ruiva (this is the highest point in the region, with 370m), Serra de S. Barão and Serra de Alvares; and the embedded valleys of the Guadiana River and its affluents marked by the rugged banks and coated by the Mediterranean scrublands.
Apart from the Guadiana river, the valley is transversed by several water paths, such as: Vascão, Carreiras, Oeiras, Terges e Cobres and Limas. While in summer the streams tend to be quite low (or in some cases even dry), in winter the flow increases significantly, leading to the rise of the Guadiana river flow.
BIOPHYSICAL CHARACTERIZATION
CLIMATE
This is a region in which the climate is typically Mediterranean, in other words hot and dry summers contrasting the mild rainy winters.
Here, the average annual temperature is 16.5° C. In the coldest month which is January, the average minimum temperature is 4.7º C. In the hottest month, in August, the heat reaches about 33.8° C.
It is also here where the lowest rainfall of the country is registered. The annual average does not exceed 500 mm. It rains mostly between October and March, in the remaining months the rain is practically non-existent.
In the month of July, there are about 367 hours of sunshine; while in December and January, the values fall to about 149 hours.
The winds are predominantly from the northwest quadrant and the average annual speeds are between 7.8 km/h and 9.8 km/h.
BIOPHYSICAL CHARACTERIZATION
GEOLOGY AND SOILS
We find ourselves in the “South Portuguese Zone”, in one of the units of the Hesperian Massif, where the rock formations of the territory are proof of a history of millions of years.
An area consisting mainly of metamorphic rocks (such as schist, greywacke, sandstone, conglomerates), crossed by a Pyrite Range that extends from Seville to Grândola. It is made up of volcanic rocks that form a mineralized structure of great relevance and economic impact.
This Range has mining resources of great economic importance to Portugal, especially concerning the second half of the 19th century and first half of the 20th century. The former mining operations of the S. Domingos Mine or the Balança Mines (between the villages of Alcaria Ruiva and Azinhal) are some examples.
Most of these soils are lithosols (skeletal soils) and Mediterranean soils, which are characterized by low agricultural capacity and low water retention capacity. They are considered unsuitable for agricultural production and showing high sensitivity to erosion.
The geological formation of Pulo do Lobo, a 20m high narrow waterfall on the Guadiana River, is one of the most important geosites in the Natural Park area.
