Error in High–Resolution Satellite Rainfall Products in Streamflow Prediction in Birr Watershed, Ethiopia
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Date
2013-05
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Addis Ababa University
Abstract
The main objective of this study is to evaluate the performance of high – resolution satellite rainfall products (TMPA 3B42RT, 3B42V6, and 3B42V7) under sparse ground based data and complex topography medium sized watershed (Birr at 952.8 km2 ) in Blue Nile River basin Ethiopia through semi – distributed hydrological model HBV – light for daily streamflow simulation. First, the model is calibrated for the watershed to average rainfall input from rain gauge for the period of 2003 – 2008. Then the calibrated parameter values are used for daily streamflow simulations using rainfall input from each satellite products; comparison of the magnitude of rainfall and simulations to the observed streamflow at the outlet of each watershed forms the basis for the conclusions of this study. The comparison results of rainfall magnitudes revealed that both new version 7 TMPA 3B42RT and 3B42V7 rainfall estimates gave reasonably accurate result compared to rain gauge rainfall estimates. This result reveals that, in this region, 3B42RT accurately estimated the total average rainfall with negligible bias, but underestimated the seasonal rainfall with % bias less than - 11 %; while very small overestimation of average seasonal and total rainfall observed in 3B42V7 rainfall estimates with % bias less than 6%. However; version 6 TMPA 3V42V6 rainfall estimates consistently underestimated both the total and seasonal rainfall with % bias greater than – 40%, which probably suggests that rainfall estimates based on TMPA 3B42V6 can’t be a replacement of rain gauge measurements in this region. The result of this study revealed the applicability of satellite rainfall products as an input in hydrological model to simulate streamflow. Simulation from all rainfall inputs captured the trend of observed hydrograph with slight underestimation of large flood events. Simulation based on the new version 7 of TMPA 3B42RT and 3B42V7 gave reasonably accurate streamflow simulation for large flood events compared to others. On the other hand, the 3B42V6 simulation shows poor performance which underestimates consistently the daily streamflow. Dense rainfall network for rainfall measurement and stage – discharge rating curves should be given priority to improve the comparison results. Key words: Satellite rainfall products, HBV – light model, Birr watershed.
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Keywords
Satellite Rainfall Products;Hbv ;Light Model; Birr Watershed