Awash River

(2015) The Awash River basin, spanning 23 administrative zones, covers 10% of Ethiopia's area and hosts about 17% of its population. 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. 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. 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 as far north as 12° before turning completely east to reach lake Gargori. Other tributaries of the Awash include (in order upstream): the Logiya, Mille, Borkana, Ataye, Hawadi, Kabenna and Dukem Rivers. Towns and cities along its course include Metehara, Awash, Gewane and Asaita. There are tributary rivers, lakes, hot springs, and swamps in the Middle Awash Basin. == 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 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 ==

s 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 . 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 and in southern Afar. The Awash Basin is a densely populated and industrialized area where numerous enterprises rely on groundwater for their operation. Therefore, the majority of human development initiatives in the basin will continue to depend heavily on the quantity and quality of groundwater. Groundwater management requires proactive measures due to the global challenges posed by rapid population growth, urbanization, climate change, and various human activities. == 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. 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 ==

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. Over half of the groundwater sources were unsuitable for drinking, posing significant health risks to local communities that rely heavily on these sources due to limited access to clean surface water. In the Middle Awash Basin and the country at large, the water quality of most groundwater sources is inadequately monitored and insufficiently regulated. Consequently, areas within the upstream Awash Basin, particularly around Modjo, Bishoftu, Gelan, and Addis Ababa, are highly susceptible to unregulated abstraction and pollution of groundwater. == Paleontology ==

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 ==

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

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. == See also ==