Quebrada: what it is, characteristics and how it is formed

In geography, a ravine is defined as a narrow, deep valley with steep slopes, which forms mainly in mountainous or steep-sloping regions. Its origin is usually associated with the erosive action of water, which wears down the land over time, although it can also be due to tectonic movements.

A stream or river usually flows at the bottom of the stream, permanently or seasonally, depending on the rainfall pattern that occurs. This contribution of water generates special conditions that allow the development of vegetation and different animal species, turning the streams into ecosystems of great ecological importance.

You may also be interested in reading this article about a River Valley: what it is, how it is formed and examples.

The streams have a series of their own characteristics, such as:

• They have steep slopes and steep slopes: ravines usually have very steep slopes with steep slopes. This form of relief favors rapid water runoff and erosive processes, in addition to generating strong contrasts between the regions that solar radiation reaches and those that remain in shadow, thus creating microclimates with very particular characteristics.
• There is great seasonal variation in water flow: many streams have streams or water courses that operate seasonally. In rainy seasons the flow increases, while in dry seasons it can be greatly reduced or even dry temporarily.
• They present good quality waters: In many streams, the water that circulates remains relatively clean and little altered by human activity. Studies carried out in different places show that they usually have low levels of nutrients such as nitrogen, which indicates little contamination. In addition, characteristics such as pH, conductivity or the amount of minerals depend largely on the type of rocks and soils through which the water flows.
• They are environments that conserve high humidity and allow the formation of microclimates: in ravines a lot of humidity is conserved, whether in the soil, in the vegetation or even in the form of mist. This happens especially in the most closed and shaded parts, where almost no sunlight enters. Thanks to the presence of these variables, microclimates are generated that allow the presence of species adapted to these conditions.
• They have fertile soils with a greater water retention capacity: in many cases, especially where there is dense vegetation, the soils of the ravines (or their margins) have greater organic matter and better structure, which improves the retention of moisture and nutrients, compared to more exposed slopes.
• They are environments rich in biodiversity: due to the diversity of existing microhabitats (differences in light, temperature, humidity), many streams are home to a wide variety of flora and fauna species and even numerous endemic species.
• They intervene in water regulation: streams intervene in water collection, recharge aquifers, cushion runoff, reduce flood peaks in the lower parts of basins, and act as temporary water reservoirs in episodes of heavy rain.
• They are vulnerable to human disturbances: being on slopes, with loose slopes, presence of water, humid and fragile soils, streams can be very sensitive to different anthropogenic activities such as deforestation, urbanization, contamination of streams, modification of the channel, etc. This can cause accelerated erosion, landslides and even loss of biodiversity.

Streams originate mainly from the erosive action of water over time. When the rains are intense or frequent, the runoff water begins to wear down the land, opening furrows that, over the years, deepen until forming a narrow, boxed valley. In many cases, this erosion is favored by the slope of the relief, since in mountainous areas or with marked unevenness the water descends with greater force, increasing its capacity to drag sediments and rocks.

Another way in which ravines can arise is from tectonic activity, when the movements of the Earth’s crust generate fractures or subsidence in the ground that are then used by water to open its path.

A ravine is a narrow, deep valley formed by water erosion or tectonic processes. That is, it is a type of geographical feature that opens between mountains or steep slopes. At the bottom of that stream water may or may not circulate. On the contrary, a river is a course of fresh water that flows continuously, more or less abundant, from its source to its mouth. The river is water in motion.

Does a stream always have water?

Not necessarily. Many streams have streams or rivers that flow only in the rainy season or after storms, while in the dry season they may have little flow or even dry out. Others, however, maintain water permanently thanks to springs or the accumulation of frequent rains.

What is the importance of streams?

Streams act as natural corridors (biocorridors) that connect different environments and allow the movement of species. In addition, they regulate water flow and allow the recharge of aquifers. They also help prevent flooding and generate microclimates where a great diversity of species thrives. In many cases, they have a high cultural and tourist value.

What flora and fauna live in the streams?

The flora and fauna of the ravines varies greatly depending on the region, climate and altitude. In humid environments, such as those of the subtropical northwest or in yunga areas, it is common to find ferns, mosses, lichens, riverine trees and a great diversity of birds, amphibians and insects.

On the other hand, in streams in arid environments such as the Quebrada de Humahuaca, the vegetation is dominated by cardones, xerophytic shrubs and species that tolerate the lack of water and strong thermal oscillations well. There, the fauna includes birds typical of dry areas, reptiles and mammals adapted to water stress.

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