Mereb River

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Mereb River

The Mereb River, also known as the Mareb River or the Gash River, is a river in East Africa. It starts southwest of Asmara in central Eritrea and flows south along the Eritrea–Ethiopia border, then west through western Eritrea toward the eastern Sudanese plains near Kassala. Most years the river is dry and only carries water during the rainy season; the water often dissipates in the sands of eastern Sudan, forming an inland delta. Its waters usually do not reach the Nile.

Course and size
- Length: about 440 kilometers (270 miles).
- Basin: estimates vary. Ethiopian catchment is reported around 5,700 square kilometers, while the total basin is sometimes given as 21,000 to 44,000 square kilometers.
- Discharge: average around 21.6 cubic meters per second, with higher peak flows during floods.

Tributaries
- Right bank (Eritrea): Obel River.
- Left bank (Ethiopia): Sarana, Balasa, Mai Shawesh, and Engweya rivers.

History
The Mereb has long served as a boundary between Bahr negash (Medri Bahri) to the north and the Ethiopian region of Tigray to the south. The Bahr negash extended to the Red Sea coast, and Debarwa near Asmara was a historic capital.

Wildlife
The river’s Eritrean floodplain was the site of a large elephant herd sighting in 2001, the first such sighting in Eritrea since 1955.

Mouth and context
The river ends in the eastern Sudanese plains. Because the river often dries up, its waters usually do not flow into the Nile and instead form an inland delta.