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ARPN Journal of Science and Technology >> Volume 7, Issue 1, January 2017

ARPN Journal of Science and Technology


Prediction of Runoff and Sediment Yield Using AnnAGNPS Model: Case of Erer-Guda Catchment, East Hararghe, Ethiopia

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Author Samuel Lindi Megersa
ISSN 2225-7217
On Pages 575-595
Volume No. 4
Issue No. 10
Issue Date November 01, 2014
Publishing Date November 01, 2014
Keywords Runoff, Sediment Yield, Estimation, and Model



Abstract

Land and water resources degradation are the major problems in Ethiopia. Poor land use practices and improper management systems have been playing a significant role in causing high soil erosion rates, sediment transport and loss of soil nutrients. In this study a physically based watershed model, AnnAGNPS model was applied to the Erer-Guda river catchment for prediction of runoff and sediment yield. The objectives were to evaluate the AnnAGNPS model capability to predict the runoff and sediment yield with respect to different land use practice factors and to identify the most erodible sub-catchment of Erer-Guda gauged catchment of East Hararghe zone. Sensitivity analysis, model calibration and validation were also performed to assess the model performance. Four sensitive parameters were identified of which curve number (CN) was the most sensitive one. For model calibration, model efficiencies of 0.758, -331.068 and 0.710 were observed for surface runoff, peak runoff rate, and sediment yield, respectively. Corresponding coefficient of determination were founded to be 0.825, 0.110 and 0.763, respectively. Runoff and sediment yield were well predicted but, peak runoff rate was over predicted. Validation results produced model efficiencies (NSE) as 0.778, -77.999 and 0.779 for surface runoff, peak runoff rate and sediment yield, respectively. The coefficient of determination (R2) as 0.923, 0.235 and 0.857 for runoff, peak runoff rate and sediment yield, respectively. Surface runoff and sediment yield simulation were found better in validation stage as well as the peak runoff rate showed almost the same as for calibration. Erer-Guda catchment was simulated with respect to land use practices for runoff and sediment yield generation. Cultivated agricultural land was contributed large amount of runoff and sediment yield. Runoff and sediment yield from the contributing land use was 486mm/yr and 10.50t/ha/yr, respectively. Erer-Guda catchment was divided in seven sub-catchments. Runoff and sediment yield for each sub-catchment were quantified. The result of simulation of runoff and sediment yield after calibration for the most erodible sub-catchment (SWT-5) was 498.41mm/yr. and 17.30tons/ha/yr. respectively. In conclusion, the AnnAGNPS model can effectively be used to predict runoff and sediment yield in order to effectively design soil and water related development in absence of gauged information.


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