Awash

Geography

The Awash River basin, spanning 23 administrative zones, covers 10% of Ethiopia's area and hosts about 17% of its population. It is partly located in the Main Ethiopian Rift. The Awash River is 1,200 kilometres (750 mi) long. It starts in Ethiopia’s central highlands at an elevation of 3,000 metres (9,800 ft) and passes through a number of locations before joining Lake Abbe at a height of 250 metres (820 ft). The Awash River basin is divided into three sections: upper, middle, and lower.

The Awash rises south of Mount Warqe, west of Addis Ababa in the woreda of Dendi, close to the town of Ginchi, West Shewa Zone, Oromia.

Hydrology

Rainfall varies a lot in the basin from one year to the next (this is called high intra-annual variability). Dry season water shortage is recognized as a challenge for various activities such as irrigation and domestic water supply by the Awash Basin Authority. However, flooding also occurs frequently during the main rainy season in July and August. The type of flooding is different for the upper, middle and lower Awash basin. Research has found that "the type and range of flooding in the Awash Basin varies widely reflecting the basin’s complex geography". For example, in urban areas, flash floods and river overflows are known to occur.

History

In the 16th century the Awash River was called the great Dir river and lay in the country of the Muslims.

The first European to trace the course of the Awash to its end in the Aussa oasis was Wilfred Thesiger in 1933/1934, who started at the city of Awash, followed the river's course to its final end in Lake Abhebad, and continued his expedition east to Tadjoura. (Although the explorer L. M. Nesbitt had followed parts of the course of the Awash in 1928, he turned away from the river at Asaita and proceeded north through the Afar Depression to the Red Sea.)

In 1960, the Koka Dam was completed across the Awash River at a point around 75 kilometres (47 mi) from Addis Ababa. With its opening, it became a major source of hydroelectric power in the area.

Ecology

Most of the Awash basin is part of the Ethiopian montane forests ecoregion. At high altitudes the Ethiopian montane grasslands and woodlands and Ethiopian montane moorlands predominate. The Somali Acacia–Commiphora bushlands and thickets ecoregion occupies low elevations in the Rift.

The basin's vegetation has a strong anthropogenic impact. All over the upper and central Awash basin, remains of different savanna types are still clearly visible. They range from thorn savannas in the lower rift, bush, grass and open savannas above 800 m and woody savannas on the escarpments and the highlands.

The lower Awash Valley is one of the last wildlife preserves for the African wild ass.