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Please use this identifier to cite or link to this item: http://hdl.handle.net/123456789/2272

Authors: Yacob, Esayas
Advisors: Prof. Tenalem Ayenew
Copyright: Mar-2010
Date Added: 3-May-2012
Abstract: Abstract Rapid increases in population, forest clearing and continuing search for a farm land have induced pressure on natural resource. In order to reverse such kind of problem assessing the level of problem and finding solution at watershed level is necessary. The studies of land use land cover changes and their effects on soil erosion and runoff patterns at the watershed level are essential in water resource planning and management. This study provides an approach to identify the effects of land use land cover changes on runoff and sediment in Tikur Wuha watershed. The changes in land use land cover were associated with growing demand of wood for fire, charcoal, construction materials, household furniture, pulp and paper industries, and expansion of farming and grazing land. By apply GIS technique with computer model in analysis of soil erosion and runoff, this study estimates the sediment yield due to soil erosion, evaluate the yearly sediment transport rates of the rivers flowing into the lake and examine the effects of change in land use land cover on water yield. Daily meteorological data of Awassa and Haissawita station, 1965 and 2004 land use map, soil map and daily and monthly Tikur Wuha river flow data were used and analyzed using SWAT model. The runoff and soil loss simulation were done by dividing the watershed into eight subwatersheds and by assigning a hydrological response unit based on multiple HRU definition. This study presents the calibration and validation of SWAT for the stream flow for two periods, 1990-1995 and 1996-2000. The simulation result showed that runoff and soil loss were increased through out the simulation period. Model predictions on monthly basis show a strong relation between water yield and land use change during the calibration and validation periods, as indicated by coefficient of determination (R2) and Nash- Sutcliffe simulation efficiency (E), 0.751 and 0.603 for calibration results and 0.848 and 0.738 for the validation respectively. As a result the annual water yield was found with in the ranges of 459.546 mm to 757.48 mm for the 1965 land use and from 498.223mm to 766.453mm for the land use 2004. Higher value of the surface runoff correlated with Orthic Luvisols soil type and bare and open shrub land use system. The final actual erosion result for the catchment also shows that the value ranges from 0.162t/ha/year to 1.823 t/ha/year for the land use in 1965 and from 0.132t/ha/year to 1.75t/ha/year for land use type in 2004. The mean erosion rate is 0.67and 0.89 t/ha/year for 1965 and 2004, respectively. The study also indicated land use /land cover change in the last 39 years (1965 to 2004), the dense wood land, dense bushy wood land, dense shrub land and wetlands-non forested changed in to bare land, open bush land, open shrub land, and swampy iii grass land. The findings of this particular study suggested that deforestation and soil erosion problems need to be given due attention urgently to maintain the stability and resilience of the ecosystem.
URI: http://hdl.handle.net/123456789/2272
Appears in:Thesis - Environmental Sciences

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