Tanqwa

It is a confined river, locally meandering in its narrow alluvial plain, with a slope gradient of 25 metres per kilometre. With its tributaries, the river has cut a deep gorge. Tributaries Tributaries, upstream from Abiy Addi, include • Tsech'i River • May Qoqah • Arwadito • Adawro River ==Hydrology==

Hydrological characteristics The runoff footprint or annual total runoff volume is 41 million m³ at the bridge in Abiy Addi and 79 million m³ at the confluence with Giba River at Barashuwa. Peak discharges up to 543 m³ per second occur in the second part of the rainy season (month of August) when there are strong rains and the soils are saturated with water in many places. The percentage of total rainfall that directly leaves the catchment as storm runoff (also called runoff coefficient) is 23%. As such water contains many nutrients (locally it is called "aygi"), farmers estimate that it strengthens their cattle, which they will bring to the river. Up to the 1980s, there was strong pressure on the environment, and much vegetation disappeared. This river had its greatest discharges and width in that period. The magnitude of floods in this river has however been decreased in recent years due to interventions in the catchment. On other steep slopes, exclosures have been established; the dense vegetation largely contributes to enhanced infiltration, less flooding and better baseflow. Physical conservation structures such as stone bunds and check dams also intercept runoff. ==Transhumance towards the river gorge==

The valley bottoms in the gorges of this river have been identified as a transhumance destination zone. 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. ==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. • Phonolite plugs • Upper basalt • Interbedded lacustrine deposits • Lower basalt • Amba Aradam Formation • Antalo Limestone • Adigrat Sandstone • Edaga Arbi Glacials • Precambrian basement rocks ==Natural boundary==

During its course, this river passes through nine municipalities and three woredas and constitutes six different borders. From upstream to downstream: • Border between Hagere Selam and Melfa, both in Dogu’a Tembien • Border between Lim'at and Melfa, both in Dogu’a Tembien • Border between Aregen and Melfa, both in Dogu’a Tembien • Border between Aregen and Degol Woyane, both in Dogu’a Tembien • Border between Aregen (Dogu’a Tembien) and Geramba (Kola Tembien) • Crosses the town of Abiy Addi • Border between Kola Tembien and Abergele (woreda) ==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 6, along the middle Tanqwa course • Trek 20, along the upper Tanqwa course In the rainy season, flash floods may occur and it is advised not to follow the river bed. Frequently, it is then also impossible to wade across the river. == See also ==