Ab'aro

The Ab’aro is a river of the Nile basin. Rising in the mountains of Dogu’a Tembien in northern Ethiopia, it flows northwestward to empty into the Weri’i, which is a tributary of Tekezé River.

The Ab’aro is a confined ephemeral river in its upper part, whereas it widely meanders in the lower plains, with an average slope gradient of 60 metres per kilometre. Towards the footslope the river has cut a deep gorge (a cluse).

Runoff mostly occurs 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. In contrast to neighbouring rivers such as May Meqa, May Sho'ate or Graliwdo, the magnitude of floods in Ab’aro has not been decreased due to interventions in the catchment. Physical conservation structures such as stone bunds and check dams that intercept runoff are absent. On the steep slopes, exclosures have not been established and there is no dense vegetation that could contribute to enhanced infiltration, less flooding or better baseflow. As such, it is one of the few catchments that could stand model for conditions before major human interventions for conservation started in the Tigray region.

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 Quaternary freshwater tufa Adigrat Sandstone Logically, in the uppermost stretches of the river, only the pebbles and boulders 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.

Flows through: Ethiopia.

River data from Wikidata (CC0); lengths normalised to a common unit.