Hydrological Models Comparison for Estimation of Floods in The Abaya-Chamo Sub-Basin
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Date
2008-06
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Addis Ababa University
Abstract
Nowadays the major environmental disasters in Ethiopia are recurrent droughts and floods. Their socio-economic and ecological impacts are devastating to the entire country, because most of them do not have real time forecasting technology or resource for post disaster rehabilitation. The Abaya-Chamo river basin is located in the southern part of Ethiopia. The extensive and attractable areas of this region, apart from being densely populated and extensively used for agriculture are also considered as a flood prone. Since most of the rivers in the basin are ungauged, it is essential to now the flow characteristics of the rivers in order to mitigate flooding effects in the basin. The aim of this study is to test the three conceptual hydrological models and propose suitable model for the estimation of floods in the ungauged catchments of the basin. Two catchments; Kulfo catchment from medium sized and Bilate catchment from large sized catchments, are selected for the analysis. Model approaches selected are: Soil Moisture Accounting (SMA) model which is embedded in the HEC-HMS software suite. SMA is a lumped, event, conceptual approach that allows continuous stream flow simulation and a number of model parameters are estimated. The other two models RRL SMAR & RRL TANK models are conceptual continuous daily time series models. Default values of all the parameters are used and then calibration has been made manually and automatically.
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Using various models performance evaluation criteria; Nash-Sutcliffe efficiency, NSE (Coefficient of efficiency), Index of agreement d, Coefficient of determination R2
, index of volumetric fit IVF and The relative error of the peak, the output of each models was evaluated. HEC-HMS SMA model performed well compared to the other models especially with the objective of capturing the peak flow and volumetric fit IVF in the two catchments. Thus, the HEC-HMS SMA model can be used for the estimation of peak floods in the two catchments and in the ungauged catchments with or without regionalization. Model uncertainties due to various sources such as improper data input, incorrect model parameterization are also highlighted in the end of this study. Keywords: Ungauged catchment, floods, HEC-HMS SMA, RRL SMAR, RRL TANK, Abaya-Chamo river basin.
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Keywords
Ungauged Catchment, Floods, Hec-Hms Sma, Rrl Smar, Rrl Tank, Abaya-Chamo River Basin