Awash River

The Awash River (sometimes spelled Awaash; Oromo: Awaash or Hawaas, Amharic: ዐዋሽ, Afar: Hawaash We'ayot, Somali: Webiga Dir, Italian: Auasc) 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 begins with Lake Gargori and ends with Lake Abbe (or Abhe Bad) on the border with Djibouti, about from the head of the Gulf of Tadjoura. The Awash River 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 River basin, spanning 23 administrative zones, covers 10% of Ethiopia's area.

The Awash River basin is the most developed, utilized, abused, impacted, and most populous (over 15% or nearly 18.6 million out of 120 million) basin in Ethiopia (as of 2021). Rapid growth of agriculture, industries and urbanization within the basin, as well as population growth is placing increasing demands on the basin's water resources. The main sources of water pollution in the upper Awash basin come from industrial and urban wastes, agricultural runoff (pesticides, fertilizers), and sewage discharge. Polluting industries in the basin include tanneries, paint factories, slaughterhouses, textiles, breweries, soft drink factories, sugar factories, hospitals, and pharmaceuticals. "Lucy", one of the most famous early hominin fossils, was discovered in the lower Awash Valley. It starts in Ethiopia’s central highlands at an elevation of and passes through a number of locations before joining Lake Abbe at a height of . The Awash River basin is divided into three sections: upper, middle, and lower. Semi-arid to arid conditions prevail in the Rift Valley. In contrast, the highlands partly receive more than 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. The type of flooding is different for the upper, middle and lower Awash basin. For example, in urban areas, flash floods and river overflows are known to occur.

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. Groundwater is predominantly recharged at the escarpments and highlands above 1,900 m a.s.l., where annual rainfall is higher than .

The basin's vegetation has a strong anthropogenic impact.

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.

Human activities and impacts

thumb|Illustration of a camel convoy on the Awash River in the nineteenth century by [[Guglielmo Massaia]]

The Awash basin is the most developed, utilized, abused, impacted, and most populous (over 15% or nearly 18.6 million out of 120 million) basin in Ethiopia.

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.

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. 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.

The river water and shallow groundwater are intrinsically connected. Contaminants in the river water can pollute the groundwater and vice versa. A study in 2024 investigated the characteristics of groundwater in a region of Middle Awash for multipurpose use. It found that contaminants such as arsenic, vanadium, gallium, lithium, rubidium, chromium, manganese, copper, and zinc were found enriched in groundwater near Lake Beseka, majorly influenced by geogenic activities, volcanic ash, and weathering of rocks. 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.

thumb|upright=1.2|The Koka Dam before it was completed 1960, creating the [[Koka Reservoir]]

20th Century

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 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 . Both lake and dam are threatened by increasing sedimentation.

Society and culture

thumb|The Awash River, forded by camel caravan, a nineteenth century engraving (in 1852)

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

The Awash International Bank is named after the Awash River.