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Accueil du site → Master → Pays Bas → 2013 → Water balance of the Juba and Shabelle rivers in Ethiopia-Somalia : [assessment of water balance components and water demands]

UNESCO-IHE Institute for Water Education, Delft (2013)

Water balance of the Juba and Shabelle rivers in Ethiopia-Somalia : [assessment of water balance components and water demands]

Sebhat, M.Y.

Titre : Water balance of the Juba and Shabelle rivers in Ethiopia-Somalia : [assessment of water balance components and water demands]

Auteur : Sebhat, M.Y.

Université de soutenance : UNESCO-IHE Institute for Water Education, Delft

Grade : Master of Science (MS) 2013

Résumé
The Juba and Shabelle Rivers are the only perennial and transboundary rivers in Somalia but two-thirds of the river basins are located outside Somalia, mostly in Ethiopia, with a part of the Juba basin in Kenya . The catchment area of the Juba River is 218,114 km2at Jamame and for the Shabelle River basin it is 296,976 km2at the Juba confluence. Although the Shabelle River has a larger drainage area than the Juba River, the flow in the Juba River is much higher. The two rivers originate from the Bale mountain ranges at an altitude of about 4230 m in the Ethiopian highlands flowing towards the Indian Ocean crossing the border between Ethiopia and Somalia. The thesis deals with a characterization of the hydrometeorology, the water balance, and the demands and users in the Juba and Shabelle River basins. The study area was delineated using a 30 m resolution Shuttle Radar Topography Mission (SRTM) digital elevation model. To fulfil the research objectives, the rainfall and daily runoff data were collected from the FAO SWALIM project office and database, theLocClim v.1.10 database and the TRMM satellite product. The daily runoff data was stored and analyzed using the HEC-DSSVue 2.0.1 system for the basic statistical analysis and a correlation testing of TRMM data and measured rainfall data.The areal rainfall was calculated using the Thiessen polygon method with the ArcGIS software and the actual evaporation was determined using the water balance method. Water users and demands along the Juba and Shabelle Rivers were modelled using a WEAP model.The Juba and Shabelle Rivers have two peak flows during the Deyr (October to December) and Gu (April to June) flood seasons. The river peak flows occur in October and September in the Juba and Shabelle rivers, respectively. The Shabelle River flow is decreased at the downstream runoff stations during the two peak flow seasons but there is only a very small flow reduction in the Juba River. The annual daily peak flows were observed for the Juba River at the Luuq runoff station and for the Shabelle River at the Belet Weyne runoff station, but during the Hagaa (July to September) and Jilaal (January to March) seasons the daily flow for the two rivers are very low and even close to zero.The actual evapotranspiration was determined as a remaining part of the water balance equation and it is mainly depended on the rainfall in each sub basin. The actual evapotranspiration contribution from the two rivers was almost negligible and ignored in the study area. This is due to nearly negligible surface runoff contribution from each sub basin in Somalia and the sub basin areas are large compared to the river cross section that contributes to evaporation.The long-term mean annual flow volume at Luuq and Belet Weyne runoff stations were 5,638 and 3,499 mcm in the Juba and Shabelle Rivers, respectively. If maintaining the existing irrigation infrastructure along the rivers, irrigation water demands or the year 2035 are 3% and 63% of the annual flow volume at the Juba and Shabelle Rivers, respectively.

Sujets  : water balance river basins water demand rainfall Ethiopia Somalia

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Page publiée le 10 février 2020