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Norwegian University of Science and Technology (NTNU) 2011

Hydrological modelling in east Gojjam Region, Ethiopia

Asfaw, Betemariam Assefie

Titre : Hydrological modelling in east Gojjam Region, Ethiopia

Auteur : Asfaw, Betemariam Assefie

Université de soutenance : Norwegian University of Science and Technology (NTNU)

Grade : Master thesis 2011

Résumé partiel
The Blue Nile River is known for its huge hydropower potential. Future sustainable planning and management of the river system require advanced approaches in hydrological analysis. Rainfall-runoff models are one of the hydrological tools that can be used for runoff forecasting (real-timeforecasting), flood forecasting, generation of runoff time-series from meteorological data(precipitation and air temperature), filling-in of missing runoff observations, quality control of runoff data, determining the effects of land use changes in a catchment and studying the effects of climate change.In this study, two types of rainfall-runoff models : a lumped conceptual model( HBV) and a distributed physically based model (LANDPINE), both widely used at the Department of Hydraulic and Environmental Engineering at NTNU, were applied to compare their performance in the East Gojjam region, part of the Blue- Nile basin. Different evapotranspiration computation methods were also compared with measured evapotranspiration to determine the best method for assessment of climate impact. The achieved Nash-Sutcliffe efficiency coefficient (R2) values were 0.76 and 0.78 for LANDPINE and HBV models respectively which showed the acceptable performance of both models on the Chemoga catchment. The higher R2, less data requirement, less time (cost) of model set up, its flexibility to be integrated with daily evapotranspiration computation, and the purpose of the applications made the HBV model to be selected for further model applications over the LANDPINE model. Among the different methods of computing Potential evapotranspiration, the Thornthwaite method was found to be more representative and had the best fit to the observed records. However, to achieve this, an adjustment of the heat index on the original method and conversion into daily equivalent (by using temperature anomalies) were made. The potential of the HBV model to improve quality of flow data (i.e. filling missing data and estimating flow for nearby rivers) was found sufficient, even though, the monthly average of simulated flow on Jedeb and particularly Temcha rivers by HBV model showed lower values than the observed flows. This may have been due to the lack of meteorological data collected within these catchments.


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