Judul : Intermittent vs Perennial streams in the Mediterranean
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Intermittent vs Perennial streams in the Mediterranean
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| In mid-June in western Turkey (town of Alabair, near Chine river basin) a very rare permanent stream; There is a type of fish. Note that there are few deciduous trees and shrubs in the coastal area. |
Disruption of flow: an elusive concept
Most people don't consider the most important characteristic that defines a stream ecosystem: persistent or persistent flows. I think the Australians call it "transient flow". It is an important problem in countries with a warm and semi-arid climate. Mediterranean climate regions have summer periods with little or no current; they are an important limiting ecological factor in these ecosystems. There seems to be a threshold and a breaking point. After regular drying for several months, these river systems have the following characteristics: Periodic. That is why they are considered temporary flows: There are temporary flows.
Before human modification, many permanent or transient currents were actually permanent! Very few people know (or seem to care). Therefore, what we see today are "artificially interrupted flows" due to anthropogenic pressures (for example, excessive pumping of aquifers, springs, excessive absorption of surface water, dams, etc.).
The streams are different, there are many species in the Mediterranean.
Many small clothes dry naturally due to local climatic conditions: long periods of natural drainage cause rivers to dry for a long time (e.g. more than 4 months). Of course, they are periodic. Without groundwater and moist shelters for completely aquatic inhabitants, we have very little aquatic biota to adapt to. These natural periodic flows are interesting, full of wonder and semi-aquatic life, but they differ from permanent systems: deciduous trees, less moisture, increasingly hardy fish, other plant communities, various species of aquatic insects; many terrestrial species living in riverbeds.
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| An artificially interrupted stream in western Turkey, near Karpuzlu; this is where most of the water is taken for agriculture and large areas are drained for months. summer of 2014 |
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| A small intermittent stream in east-central Greece near Lamia in early June. One species of fish, sperchios barbel, is found in small tanks. During winter and spring floods, fish migrate up and down. summer of 2014 |
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| The mentioned stream is 4 km downstream from the mentioned area; Near Lamia, Greece. Bone dry in early June; there is no fish Is it natural or artificial time? Large trees such as maples are a good indicator of the presence of groundwater. Below the river there may be a humid hyporheic zone. summer of 2014 |
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| The Xeropatamos River on the island of Samothraki is a continuous natural flow (now completely cut off due to increasing diversion of water for agriculture). The river bed is wide and is an interesting stony habitat for the local terrestrial biota. End of July photo. Note that there are no leafy trees on the shore. summer of 2014 |
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| Erasinos Current in Attica, Greece (Vavrona outside Athens) in February 2014. This stretch is an artificially interrupted stretch, without fish and with reduced riparian vegetation. Up the river - about 3 km - there are springs that bring water and fish all year round. |
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| Fishing in a small irregular stream in south-eastern Cyprus, the Oroklini stream south of the Larnaca-Pyla national road. The stream has now been made artificially permanent, as the water rises through the growth of its own small pond! Mosquitoes and eels can be found in this area (opposite Lake Oroklin). winter 2012 |
Definitions for educational purposes:
A permanent stream is a well-defined channel that carries water throughout the year during a year of normal rainfall. The water environment of the river bed is below the water table for most of the year. Groundwater is the main source of permanent stream water, but it also carries rainwater runoff. Flow can be significantly supplemented with storm drains. Hydrological and physical properties are often related to the continuous transport of water.
An intermittent stream is a well-defined channel that contains water only part of the year, usually in winter and spring when the stream is below the water table. No water - in "dry" conditions for at least three months in a significant part of the stream (in a normal year). Entire stretches of river (dozens of kilometers are usually dry in summer). Usually riparian and aquatic vegetation differs in a similar permanent flow.
Transient Flow - Transient flow refers to a feature that conveys only stormwater in direct response to rainfall, with the water flowing immediately during and immediately after a major rainfall event. Whether a branch may have a well-defined channel or not, the water channel is always above the water table and the storm drain is the main source of water. A transient flow lacks the biological, hydrological, and physical properties associated with continuous or discontinuous water transport. In the Mediterranean region, deciduous trees are generally absent in riparian areas of ephemeral streams.
I will update you on this matter in the near future.
- Check this link for general development by state:
Bioassessment of intermittent versus constant flow, Arizona, USA
- For a more recent European approach developed by the MIRAGE project, in which HCMR also participated, see:
A new approach to the study of temporal flow regimes in relation to the control over the composition and structure of aquatic biota
- Another comprehensive presentation of classification approaches comes from the MIRAGE project, in which HCMR also participated:
THE_MIRAGE_TOOLBOX_AN_INTEGRATED_ASSESSMENT_TOOL_FOR_TEMPORARY_SREAMS
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