Awash River

Lower Valley of the Awash

UNESCO World Heritage Site
Map of the Awash drainage basin
Location	Ethiopia
Criteria	Cultural: (ii)(iii)(iv)
Reference	10
Inscription	1980 (4th Session)

The Awash (sometimes spelled Awaash; Oromo: Awaash OR Hawaas, Amharic: ዐዋሽ, Afar: Hawaash We'ayot, Somali: Webiga Dir) is a major river of Ethiopia. Its course is entirely contained within the boundaries of Ethiopia and empties into a chain of interconnected lakes that begin with Lake Gargori and end with Lake Abbe (or Abhe Bad) on the border with Djibouti, some 100 kilometres (60 or 70 miles) from the head of the Gulf of Tadjoura. It is the principal stream of an endorheic drainage basin covering parts of the Amhara, Oromia and Somali Regions, as well as the southern half of the Afar Region.

The Awash Valley (and especially the Middle Awash) is internationally famous for its high density of hominin fossils, offering unparalleled insight into the early evolution of humans. "Lucy", one of the most famous early hominin fossils, was discovered in the lower Awash Valley. For its paleontological and anthropological importance, the lower valley of the Awash was inscribed on the UNESCO World Heritage List in 1980.

Rapid growth of agriculture, industries and urbanization within the Awash basin, as well as population growth is placing increasing demands on the basin’s water resources. The basin usually has two rainy seasons, a shorter one around March (Belg), and a longer one between June and September (Kiremt), which partly fall into one longer rainy season. Climate change is predicted to increase the water deficiency in all seasons and for parts of the basin, due to a projected increase in temperature and decrease in precipitation.

Overview

The Awash River basin, spanning 23 administrative zones, covers 10% of Ethiopia's area and hosts about 17% of its population.

The Awash rises south of Mount Warqe, west of Addis Ababa in the woreda of Dandi, close to the town of Ginchi, West Shewa Zone, Oromia. After entering the bottom of the Great Rift Valley, the Awash flows south to loop around Mount Zuqualla in an easterly then northeasterly direction, before entering Koka Reservoir. There, water is used for the irrigation of sugar cane plantations. Downstream, the Awash passes the city of Adama and the Awash National Park. It is then joined on its left bank by its chief affluent, the Germama (or Kasam) River, before turning northeast at approximately 11° N 40° 30' E as far north as 12° before turning completely east to reach lake Gargori.

The Awash River is 1,200 kilometers long. The Encyclopædia Britannica Eleventh Edition's article Abyssinia, describes its middle portion as "a copious stream nearly 200 feet [61 meters] wide and 4 feet [1.2 meters] deep in the dry season, and during the floods rising 50 or 60 feet [15 or 18 meters] above low-water mark, thus inundating the plains for many miles along both its banks."

Other tributaries of the Awash include (in order upstream): the Logiya, Mille, Borkana, Ataye, Hawadi, Kabenna and Durkham Rivers. Towns and cities along its course include Metehara, Awash, Gewane and Asaita.

Paleontology

Main article: Middle Awash

Humans have lived in the valley of the Awash almost since the beginning of the species. Numerous pre-human hominid remains have been found in the Middle Awash. The remains found in the Awash Valley date from the late Miocene, Pliocene, and early Pleistocene (roughly 5.6-2.5 million years ago), and include fossils of many Australopithecines, including "Lucy", the most famous individual Australopithecus. Other extinct hominids discovered at the site include Homo erectus and Ardipithecus.

History

Awash River in the Awash National Park

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

The Koka Dam before it was completed 1960

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. The resulting freshwater lake, Lake Gelila (also known as the Koka Reservoir), has an area of about 180 square kilometres (69 sq mi). Both lake and dam are threatened by increasing sedimentation.

Climate

The climate of the Awash River Basin is mostly influenced by the movement of the intertropical convergence zone (ITCZ). During its movement northwards in March/April and its retreat southwards, ITCZ creates two rainy seasons, a shorter one around March (Belg), and a longer one between June and September (Kiremt), which partly fall into one longer rainy season. The rainy season tends to be bimodal towards eastern Ethiopia and almost unimodal towards western Ethiopia. The time between October and March is a dry season, called Bega. Semi-arid to arid conditions prevail in the Rift Valley. In contrast, the highlands partly receive more than 1,600 millimetres (63 in) of rainfall in ca. six months per year.

Climate change

A study in 2018 investigated the effects of climate change on water resources in the Awash Basin. They used three climate models from Coupled Models Intercomparison Project phase 5 (CMIP5) and for three future periods (2006–2030, 2031–2055, and 2056–2080). The models were selected based on their performance in capturing historical precipitation characteristics. The baseline period used for comparison was 1981–2005. The future water availability was estimated as the difference between precipitation and potential evapotranspiration projections using the Representative Concentration Pathway (RCP8.5) emission scenarios. The projections for the future three periods show an increase in water deficiency in all seasons and for parts of the basin, due to a projected increase in temperature and decrease in precipitation. This decrease in water availability will increase water stress in the basin, further threatening water security for different sectors.

Hydrology

Groundwater recharge varies between values exceeding 350 millimetres (14 in) per year in the upper highlands and no recharge at the bottom of the rift valley. Groundwater is predominantly recharged at the escarpments and highlands above 1,900 m a.s.l., where annual rainfall is higher than 1,000 millimetres (39 in). Localized small-scale recharge is also supposed to occur at the flanks of the rift valley volcanoes. Artificial groundwater recharge takes further place at irrigated plantations at the rift valley. Recharge from river channel losses and via infiltration from lakes plays a role in the Main Ethiopian Rift (MER) and in southern Afar.

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.

Rapid growth of agriculture, industries and urbanization within the Awash basin, as well as population growth is placing increasing demands on the basin’s water resources. The basin is known for high climate variability involving droughts and floods, and climate change will likely intensify the existing challenges. Future water management strategies should be inclusive of all sectors and consider the equity for different users.

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.

Fauna

The lower Awash valley is one of the last wildlife preserves for the African wild ass. The mammal is now extinct in Yangudi Rassa National Park, but still found in the adjacent Mille-Serdo Wildlife Reserve. Other large animals native to the area include Beisa Oryx, Soemmering's gazelle, Dorcas gazelle, gerenuk and Grevy's zebra. Crocodiles also flourish within the river.

Economic activities

The Awash Basin's economy is dominated by the agricultural and service sectors, with the latter prevailing in the large urban center of Addis Ababa. Agriculture dominates water use (about 89% of total water use in the basin) and is expected to continue to be the basis for economic growth in the coming years. Crop production in particular is a major component of the basin's economy and has seen rapid growth in recent years, with the value of output expanding by 7.9% per year in real terms between 2004 and 2014. As of 2012, the total irrigated area of the basin is less than 2% of the total area under cultivation.

Forestry hardly exists inside the Awash River Basin, with a few exceptions of small eucalyptus plantations. Outside of Awash National Park the open and woody savannas have been almost completely cultivated with crops. This especially accounts for all escarpment terraces. Thereby the scattered tree cover remained similar to the primary state of the savannas, while the grass layer has been replaced by crops. Only highest altitudes still show connected woodlands. Partly reforestation was carried out on not cultivable altitudes with secondary coniferous forests. The cultivated crops are (endemic) teff, maize, sorghum, beans and vegetables.

Pastures hardly exist where agriculture is possible. The cattle graze on field edges and waysides and on steep escarpments. This is one major reason for erosion, because vegetation cover is partly destroyed. Stubble-grazing is a common practice in the Awash Basin.

Recurrent extreme wet and dry weather events challenge economic activities in the basin. The large portion of rural poor engaged in rainfed agriculture in the drought-prone marginal lands located in the middle and lower reaches of the basin suffer greatly from recurring drought.

Climate variability already has a severe impact on populations and economic productivity in the Awash basin. Severe droughts in the basin have led to a significant depression of crop yields and death of livestock, resulting in increases in food insecurity. A modest (5%) decrease in rainfall was estimated to reduce the basin’s gross domestic product (GDP) 5%, with a 10% decrease in agricultural productivity. Humanitarian assistance requests are relatively common due to climate shocks, such as the 2015/2016 El Niño events which resulted in a severe drought and a humanitarian response targeting over 10 million people nationally, with many priority districts located in the Awash basin.

Society and culture

The valley of the Awash from about 9° N downstream is the traditional home of the Afar people and Issa people. The valley of the Awash have been included as part of the Fatagar, Ifat, and Shewa.

The Awash International Bank is named for the Awash River.

See also

• List of rivers of Ethiopia
• List of fossil sites (with link directory)
• List of hominina (hominid) fossils (with images)
• List of World Heritage Sites in Ethiopia

External links

• Media related to Awash River at Wikimedia Commons
• The Middle Awash Project website

Further reading

• Zewdu Tememew Molla, "Dam Safety Evaluation on Koka Dam, Ethiopia". M.Sc. thesis, 2005. abstract

This article incorporates text from a publication now in the public domain: Chisholm, Hugh, ed. (1911). "Abyssinia". Encyclopædia Britannica (11th ed.). Cambridge University Press.