Impact of Land Use Change on Reservoir Sedimentation (Case Study of Karadobi)

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Addis Ababa University


The Blue Nile Basin is one of the most affected areas by soil erosion, sediment transport and land degradation. The land and water resources of the basin and the ecosystem are in danger due to the rapid growth of population, deforestation, overgrazing, soil erosion, sediment deposition, storage capacity reduction, drainage and water logging, flooding, pollutant transport, population pressure and over-exploitation of specific fish species. The lack of decision support tools and limitation of data concerning weather, hydrological, topographic, soil and land use; are factors that significantly hinder research and development in the area. There is a need for hydrological and sediment transport research of the Blue Nile Basin that can improve catchment’s management programs. Appropriate decision support tools are needed for better assessment of the hydrology and soil erosion processes for planning and implementations of soil and water conservation measures. The tools concern various hydrological and soil erosion models as well as geographical information system (GIS). The modelling tools will finally help to save the physical quality of the land. In this paper the influence of land use changes on catchment’s hydrology is observed particularly on sediment yield. To carry out this SWAT MODEL was used for simulation. The delineated watershed was divides into 75 sub basins and 293 HRUs by the model. Model calibration and validation was done at Kessie. In addition to this the model efficiency was checked at this station. Based on this values for coefficient of determination (r²) and Nash–Sutcliffe model efficiency (ENS) were found to be in the acceptable range i.e. (0.80 to 0.95 for r² and 0.70 to 0.92 for ENS ).The annual sediment load at Karadobi is found to be 855 ton per square kilometre. And in 50 years 7.84% of the active storage will be depleted due to sediment accumulation. Four scenarios are developed to observe the impact of land use changes. Based on this a 10 and 20% of change in agropastoral land to agricultural land has resulted in 12% and 61% increase in sediment load. But 60% and 90% change of pasture and forest lands have resulted in a sediment increment by less than 0.5%.



Geographical information system (GIS)