Mesenbet Yibeltal Sebhat
The Juba and Shabelle Rivers are the only perennial and transboundary rivers in Somalia but twothirds of the river basins are located outside Somalia, mostly in Ethiopia, with a part of the Juba basin in Kenya. 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 study area was delineated using a 30 m resolution Shuttle Radar Topography Mission (SRTM) digital elevation model. To fulfill the research objectives, the rainfall and daily runoff data were collected from the FAO SWALIM project office and database, the LocClim v.1.10 database and the TRMM satellite product. The daily runoff data was stored and analyzed using the HECDSSVue 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. The Juba and Shabelle Rivers have two peak flows during the Deyr and Gu flood seasons. 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 and Jilaal 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.
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