Gra Adiam Explained

Gra Adiam
Pushpin Map:	Ethiopia
Pushpin Map Caption:	Gra Adiam River in Dogu’a Tembien
Subdivision Type1:	Country
Subdivision Type2:	Region
Subdivision Name2:	Tigray Region
Subdivision Type3:	District (woreda)
Subdivision Name3:	Dogu’a Tembien
Length:	15km (09miles)
Width Avg:	20m (70feet)
Source1 Location:	Mashih in Seret municipality
Source1 Elevation:	2560m (8,400feet)
Source2:	May Ch’elaqot
Source2 Location:	Ch’elaqo in Inda Sillasie municipality
Mouth:	Giba River
Mouth Coordinates:	13.482°N 39.177°W
Mouth Elevation:	1445m (4,741feet)
River System:	Seasonal/permanent river
Custom Label:	Topography
Custom Data:	Mountains and deep gorges

The Gra Adiam is a river of the Nile basin. Rising in the mountains of Dogu’a Tembien in northern Ethiopia, it flows southward where its name changes to Bitchoqo. It empties in the Giba and finally Tekezé River.^[1]

Characteristics

It is a confined ephemeral river, locally meandering in its narrow alluvial plain, with an average slope gradient of 74 metres per kilometre. With its tributaries, the river has cut a deep gorge.^[2]

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). 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.^[2] The magnitude of floods in this river has however been decreased due to interventions in the catchment.

At Ch'elaqo and on other steep slopes, exclosures have been established; the dense vegetation largely contributes to enhanced infiltration, less flooding and better baseflow.^[3] Physical conservation structures such as stone bunds^{[4] [5]} and check dams also intercept runoff.^{[6] [7]}

Transhumance towards the gorge

Transhumance takes place in the summer rainy season, when the lands near the villages are occupied by crops. Young shepherds will take the village cattle down to the gorge and overnight in small caves. The gorges are particularly attractive as a transhumance destination zone, because there is water and good growth of semi-natural vegetation.^[8]

Boulders and pebbles in the river bed

Boulders and pebbles encountered in the river bed can originate from any location higher up in the catchment. 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.^[9]

• Upper basalt
• Interbedded lacustrine deposits
• Lower basalt
• Amba Aradam Formation
• Antalo Limestone
• Quaternary freshwater tufa^[10]
• Adigrat Sandstone

Natural boundary

During its course, this river passes through four municipalities and constitutes one border.^[1] On the various parts:

• The headwaters are located in Seret and Mika'el Abiy
• The main and lower course form the boundary between Walta (at the west) and Inda Sillasie (at the east)

Trekking along the river

Trekking routes have been established across and along this river.^[11] The tracks are not marked on the ground but can be followed using downloaded .GPX files.^[12]

• Trek 9 diagonally crosses the middle Gra Adiam valley
• Trek 8V, across the river and further to Dabba Hadera monastery

In the rainy season, flash floods may occur and it is advised not to follow the river bed. At times it may be impossible to cross the river in the rainy season.^[13]

See also

• List of Ethiopian rivers

Notes and References

1. Book: Jacob . M. and colleagues . Geo-trekking map of Dogu'a Tembien (1:50,000). In: Geo-trekking in Ethiopia's Tropical Mountains - The Dogu'a Tembien District . 2019 . SpringerNature . 978-3-030-04954-6 .
2. Book: Amanuel Zenebe . and colleagues . The Giba, Tanqwa and Tsaliet rivers in the headwaters of the Tekezze basin. In: Geo-trekking in Ethiopia's Tropical Mountains - The Dogu'a Tembien District . 2019 . SpringerNature . 978-3-030-04954-6 . 10.1007/978-3-030-04955-3_14 .
3. Descheemaeker. K. and colleagues. Runoff on slopes with restoring vegetation: A case study from the Tigray highlands, Ethiopia. . Journal of Hydrology . 2006 . 331 . 1–2 . 219–241 . 10.1016/j.still.2006.07.011. 1854/LU-378900 . free .
4. Nyssen. Jan. Poesen. Jean. Gebremichael. Desta. Vancampenhout. Karen. d'Aes. Margo. Yihdego. Gebremedhin. Govers. Gerard. Leirs. Herwig. Moeyersons. Jan. Naudts. Jozef. Haregeweyn. Nigussie. Haile. Mitiku. Deckers. Jozef. Interdisciplinary on-site evaluation of stone bunds to control soil erosion on cropland in Northern Ethiopia. . Soil and Tillage Research . 2007 . 94 . 1 . 151–163 . 10.1016/j.still.2006.07.011. 1854/LU-378900. free.
5. Gebeyehu Taye and colleagues. Evolution of the effectiveness of stone bunds and trenches in reducing runoff and soil loss in the semi-arid Ethiopian highlands. . Zeitschrift für Geomorphologie. 2015 . 59 . 4 . 477–493 . 10.1127/zfg/2015/0166.
6. Nyssen. J.. Veyret-Picot. M.. Poesen. J.. Moeyersons. J.. Haile. Mitiku. Deckers. J.. Govers. G.. The effectiveness of loose rock check dams for gully control in Tigray, Northern Ethiopia. . Soil Use and Management . 2004 . 20 . 55–64 . 10.1111/j.1475-2743.2004.tb00337.x.
7. Etefa Guyassa and colleagues. Effects of check dams on runoff characteristics along gully reaches, the case of Northern Ethiopia. . Journal of Hydrology . 2017 . 545 . 1 . 299–309 . 10.1016/j.jhydrol.2016.12.019. 1854/LU-8518957 . free .
8. Transhumance in the Tigray highlands (Ethiopia) . Mountain Research and Development . 2009 . 29 . 3 . 255–264 . 10.1659/mrd.00033 . Nyssen . Jan . Descheemaeker . Katrien . Zenebe . Amanuel . Poesen . Jean . Deckers . Jozef . Haile . Mitiku . free . 1854/LU-854326 . free .
9. Book: Sembroni . A. . Molin . P. . Dramis . F. . Regional geology of the Dogu'a Tembien massif. In: Geo-trekking in Ethiopia's Tropical Mountains — The Dogu'a Tembien District . 2019 . SpringerNature . 978-3-030-04954-6 .
10. Moeyersons . J. and colleagues . Age and backfill/overfill stratigraphy of two tufa dams, Tigray Highlands, Ethiopia: Evidence for Late Pleistocene and Holocene wet conditions. . Palaeogeography, Palaeoclimatology, Palaeoecology . 2006 . 230 . 1–2 . 162–178 . 2006PPP...230..165M . 10.1016/j.palaeo.2005.07.013 .
11. Book: Description of trekking routes in Dogu'a Tembien. In: Geo-trekking in Ethiopia's Tropical Mountains - The Dogu'a Tembien District . 2019 . SpringerNature . 978-3-030-04954-6 .
12. https://www.openstreetmap.org/traces/tag/nyssen-jacob-frankl Public GPS traces tagged with nyssen-jacob-frankl | OpenStreetMap
13. Book: Logistics for the Trekker in a Rural Mountain District of Northern Ethiopia. 2019 . Springer-Nature . 537–556 . 10.1007/978-3-030-04955-3_37 . Geo-trekking in Ethiopia's Tropical Mountains . GeoGuide . Nyssen . Jan . 978-3-030-04954-6 .