Climate Change Impact Assessment on Water Resources Availability (A Case Study for The Selected Catchments in Upper Blue Nile Basin)
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Date
2011-05
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Addis Ababa University
Abstract
The purpose of this thesis is to assess the significance of the climate change impact on streamflow at local scale (catchment scale) for some selected catchments in Upper Blue Nile Basin. The five catchments included in the study were Koga, Birr, Muger, Guder and Didessa Rivers. The Soil and Water Assessment Tool (SWAT) model is applied to study of the hydrology of the catchments and associated uncertainty with the simulated outputs. The SWAT model was calibrated for the period of 1992 to 2001 and validated for the period of 2001-2005. Model uncertainty was also done to establish the uncertainty bounds of the model, which is also the important boundary limit to evaluate the significance of the impact of climate change. The uncertainty analysis was done by using SUFI2 in SWAT-CUP. In the end, the climate change impact studies on water availability of the catchments were done based on the outputs of the Regional Climate Model (RegCM3) of emission scenario A1B. Overall the calibration and validation of the model was good except for Didessa. It was also shown from the model uncertainties analysis that the percentage of the simulated data within the uncertainty bound is only 24% for Didessa and 20% for Guder (P-factor=0.24, 0.20) which are relatively poor for both catchments. But for other catchments the percentage of simulated flow within the uncertainty limit during calibration and verification is more than 40% (P-factor=0.4). In general in all catchments; the impact of climate change may cause an increase in annual flow in both periods except in Koga and Didessa rivers. The estimation of the annual and monthly average flow volume changes in both period shows, the flow volume incremental range might be 48% to 185%. On the contrary, the decrement range flow in both rivers might be 0.33% to 6.7%. According to the uncertainty analysis carried out, the significance of the climatic change impacts for all catchment was analyzed. As a result it might be possible to conclude that for all catchments the impacts were significant except for Muger. Therefore, it can be deduced that climate change impact for most of the study areas might be the most sensitive than the propagated uncertainty on catchments flow.
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Water Resources, Climate Change Impact, Upper Blue Nile Basin