The Qortem Zer’a is a river of the

Nile The Nile (also known as the Nile River or River Nile) is a major north-flowing river in northeastern Africa. It flows into the Mediterranean Sea. The Nile is the longest river in Africa. It has historically been considered the List of river sy ...

basin. Rising in the mountains of Dogu’a Tembien in northern

Ethiopia Ethiopia, officially the Federal Democratic Republic of Ethiopia, is a landlocked country located in the Horn of Africa region of East Africa. It shares borders with Eritrea to the north, Djibouti to the northeast, Somalia to the east, Ken ...

, it flows westward to empty finally in the Weri’i and

Tekezé River The Tekezé River (; , originally meaning "river" in Ge’ez; , also spelled Takkaze; ), is a major river in Ethiopia. For part of its course it forms a section of the westernmost border of Ethiopia and Eritrea. The river is also known as the Seti ...

Characteristics

It is an ephemeral river, mostly

meander A meander is one of a series of regular sinuous curves in the Channel (geography), channel of a river or other watercourse. It is produced as a watercourse erosion, erodes the sediments of an outer, concave bank (cut bank, cut bank or river cl ...

ing in its alluvial plain, with an average slope gradient of 34 metres per kilometre.

Flash floods and flood buffering

Runoff mostly happens in the form of high runoff discharge events that occur in a very short period (called

flash floods A flash flood is a rapid flooding of low-lying areas: washes, rivers, dry lakes and depressions. It may be caused by heavy rain associated with a severe thunderstorm, hurricane, or tropical storm, or by meltwater from ice and snow. Flash fl ...

). These are related to the steep topography, often little vegetation cover and intense convective rainfall. The peaks of such flash floods have often a 50 to 100 times larger discharge than the preceding

baseflow Baseflow (also called drought flow, groundwater recession flow, low flow, low-water flow, low-water discharge and sustained or fair-weather runoff) is the portion of the streamflow that is sustained between precipitation events, fed to streams by d ...

. The magnitude of floods in this river has, however, been decreased due to interventions in the catchment. Physical conservation structures such as stone bunds and

check dam A steel check dam A check dam is a small, sometimes temporary, dam constructed across a swale, drainage ditch, or waterway to counteract erosion by reducing water flow velocity. Check dams themselves are not a type of new technology; rather, t ...

s intercept runoff. On many steep slopes,

exclosure An exclosure, in an area being used extensively for grazing, is a limited area from which unwanted browsing (herbivory), browsing animals, such as domestic cattle or wildlife such as deer, are excluded by fencing or other means. Environmental ...

s have been established; the dense vegetation largely contributes to enhanced infiltration, less flooding and better

Irrigated agriculture

Besides springs and reservoirs, irrigation is strongly dependent on the river's baseflow. Such irrigated agriculture is important in meeting the demands for food security and poverty reduction. Irrigated lands are established in the alluvial plain along the river, particularly west of Getski Melesiley.

Transhumance towards the gorge

Transhumance Transhumance is a type of pastoralism or Nomad, nomadism, a seasonal movement of livestock between fixed summer and winter pastures. In montane regions (''vertical transhumance''), it implies movement between higher pastures in summer and low ...

takes place in the summer rainy season, when the lands near the villages in the uplands and the lowlands are occupied by crops. Young shepherds will take the village cattle to the slopes at the river headwaters.

Boulders and pebbles in the river bed

Boulders and pebbles encountered in the river bed can originate from any location higher up in the basin. In the uppermost stretches of the river, only rock fragments of the upper lithological units will be present in the river bed, whereas more downstream one may find a more comprehensive mix of all lithologies crossed by the river. From upstream to downstream, the following lithological units occur in the catchment. ::::::::::* Upper basalt ::::::::::* Interbedded lacustrine deposits ::::::::::* Lower basalt ::::::::::*

Amba Aradam Formation The Amba Aradam Formation is a Cretaceous sandstone formation in Ethiopia. It is up to 200 metres thick, for instance in the Degua Tembien district. As fossils are absent, the age of the Amba Aradam Formation was interpreted based on the age of as ...

::::::::::*

Adigrat Sandstone The Adigrat Sandstone formation in north Ethiopia, in a wide array of reddish colours, comprises sandstones with coarse to fine grains, and locally conglomerates, silt- and claystones. Given the many lateritic palaeosols and locally fossil woo ...

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Edaga Arbi Glacials The Edaga Arbi Glacials are a Palaeozoic geological formation in Tigray (northern Ethiopia) and in Eritrea. The matrix is composed of grey, black and purple clays (locally silt), that contains rock fragments up to 6 metres across. Pollen dating yi ...

From upper to lower Tembien

During its course, this river passes through two woredas. On the various parts: * The headwaters are in Dogu’a Tembien * Most of the lower plain is in

Kola Tembien Kola Tembien (, "Lower Tembien") is a woreda in Tigray Region, Ethiopia. It is named in part after the former province of Tembien. Part of the Mehakelegnaw Zone, Kola Tembien is bordered on the south by Abergele, on the west by the Tekezé River ...

Trekking along the river

Trekking routes have been established across and along this river. The tracks are not marked on the ground but can be followed using downloaded .GPX files. * Trek 5, along upper part of the river * Trek S3, along the lower part, potentially down to

In the rainy season, flash floods may occur and it is advised not to follow the river bed. In the lower part, it may be impossible to cross the river in the rainy season.

Gallery

Image:Qortem Zer'a near Imba K'ernale.jpg, Qortem Zer’a near Imba K’ernale mountain Image:Addi Welo twds May Baha.jpg, View over Qortem Zer’a towards May Baha

References

{{reflist Rivers of Ethiopia Dogu'a Tembien Tigray Region Nile basin