Geography and Climate: River Systems and Forest Types

Key Hydrological Concepts and River Systems

• Dry season: The period during which a river reaches its lowest flow.
• Watershed: The land whose waters pour into a river and its principal tributaries.
• Headwaters of a river: The upper area of a river valley.
• River Regime: The seasonal variation in river flow, which depends on the distribution of rainfall and the importance of nival (snowfall) precipitation.
• Torrente: An intermittent watercourse that forms during times of very fast rainfall or snowmelt.
• Rambla: The course of a torrent that remains dry for much of the year.
• River Diversion: A transfer of water between surplus and deficit basins.
• Glacier Lake: A mass of water collected in basins excavated by ice in the valley of a glacier.

Ocean Climate and Deciduous Forests

The Ocean Climate corresponds to the Eurosiberian floral region. The deciduous forest is made up of tall trees with straight, smooth trunks and large leaves that fall in autumn. These trees form large masses that considerably reduce the access of light to the forest floor, allowing ferns and mosses to grow in a gloomy atmosphere within the thicket.

Characteristic Trees of the Ocean Climate

• Beech tree: Characteristic of fresh, humid mountains. It suits both siliceous and limestone soils, although it prefers calcareous ones. Its wood was formerly used for obtaining charcoal and making farming utensils; today, it is used for furniture.
• Oak tree: A tree that does not support hot summers, has a lower tolerance to cold, and requires less moisture than the beech, so it is located at lower heights. It prefers siliceous soils, and its wood is used for construction, furniture, and boats.

Mediterranean Climate and Evergreen Vegetation

The Mediterranean climate corresponds to the Mediterranean floral region. These floral formations are adapted to summer drought through various mechanisms, including the development of deep roots and hard, coriaceous leaves.

Characteristic Trees of the Mediterranean Climate

• Evergreen oak: The most characteristic and widespread tree of this drought-resistant climate. It is resistant to cold winter temperatures and is suited to all soil types. Its wood serves for external works, and its fruit is used to feed livestock.
• Cork oak: Needs mild winters, takes advantage of some humidity, and prefers siliceous soils. It is used for the construction of tools and ships, and its cortex is harvested to obtain cork.