ASSESSMENT OF THE DYNAMICS OF SUDDD SWAMP HYDROLOGY USING WATER BALANCE TECHNIQUES THE CASE STUDY OF THE BAHR EL JEBEL BASIN IN SOUTH SUDAN

Abstract

Sudd swamp area is the largest wetland in Africa, which is located in the central part or south Sudan. As results of the huge waters losses over Sudd swamp region due to evaporation. Beside reclamation of the land for development and other soci-economic activities, the area has be under raising tension, high conflicts and oppositions between managers and planners of water resources on one side and land users and environmentalists on other on how this swamp can be managed and utilized for the benefits both at locally and regionally. The objective of this study is to assess the Sudd swamp inundation area, volume and hydrological components controlling the swamp area. The method adopted to quantify the Sudd swamp water dynamics is application of the continuity equation. The monthly water balance of Sudd swamp area is determined from rainfall, evaporation, inflow and outflow of Sudd swamp region. Average rainfall for the area was estimated using Thiessen polygon for stations inside and outside the swamp area. Evaporation was estimated using Cropwat, Hamon and Thronthwaite methods. Inflow and outflow for the swamp area are time series flows measured at two stations. The potential evaporation has been estimated by the Thronthwaite method for Sudd swamp area at 170 6 mm year and the monthly averages range between 89 to 207 mm. The average monthly inundation area from 195 0 to 2009 of the Sudd area has been found range from 146 00 to 215 00 Million m 2 with mean volume of 249660. 2 Million 1113• The study also shows that the effect of climate change and human interference is very high on reduction of the fl ooding area. The increase of the temperature by three 3 "c and reducing o f rain fall amo u nt over the Sudd swamp area by 1 0 %, 15% and 25% of monthly precipitation amount , are both extr eme r e ducing the swamp inundation area from 69. 7 % up to 86 . 8 %. Also the abstraction or d iv ersion of 50% of the river in flow into Sudd swamp is reducing the swamp total annual area fr om 212211 . 19 Million ni2 to 15714 . 7 Mill m 2, which is a reduction by 92 . 6 % of the normal fl ooding areas. The total annually yield of three sub- basins ,B ahr el Jebel , Bahr el Ghazal and Sobat o utflows, which is as a total gain of White Nile is 31958 . 53 MCM/yr