ASSESSMENT OF WATER LOSSES TO RIVER BARO. IN THE BARO BASIN BETWEEN GAMBELLA AND THE OUTLET TO SUDAN

Abstract

The major objective of this thesis work is to assess the water loss situation in the Baro basin between Gambella and the outlet to Sudan. The whole basin between Gambella and Burebiey (the final outlet to Sudan) was first considered as one reach. The thesis has identified that there are significant water losses that occur in this basin. Tl_ie water balance of the monthly mean flows indicate thatthere is an average annual water loss of about 3366 million cubic meters, and the time series shows that overbank spills occur when the monthly flows at Gambella exceed about 1 . 5 billion cubic meters and the outflows through bifurcating channels start when flows at Gambella surpass one billion cubic meters. In order to exactly know where the maximum amount of losses occurs, the reach between Gambella and Burebiey was divided into three subreaches. After extending the records at all stations ( 1929-2004), the total mean annual water loss observed is about 3852 million cubic meters. In the first two subreaches minor losses are observed, and the major losses which account about 60 % occur in the last subreach, . between Jekow and Burebiey. About 92 % of these losses are due to outflow through offtaking channels and overbank spills. The paper also considered the potential evapotranspiration loss in the whole basin between Gambella and Burebiey. These losses were compared with the total water losses/spills, and it found that the former losses exceeded the latter ones. It is concluded that if the flows at Gambella are maintained .at a maximum of 1 . 5 billion cubic meters a month there would be no much inundation in this basin and, hence, people could get permanent settlement, and their properties could be secure from damage and wastage.