Application of a Satellite Based Rainfall-Runoff Estimation: in Upper Omo-Gibe Basin to Simulate the Extreme Flood Event at Omorate
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Date
2020-02
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Addis Ababa University
Abstract
Satellite-rainfall products are recognized as an essential source of rainfall data, especially in the
region where ground based measurements are unavailable. Therefore, the main objective of this
study is to Apply a Satellite based Rainfall-Runoff estimation: in Upper Omo-Gibe Basin to
simulate the extreme flood event at Omorate and with specific objective of evaluate the
capabilities, applicability and limitations of satellite rainfall products such as CMORPH, TRMM
3B42v7 and PERSIANN, and inputs of hydrological models to simulate the Rainfall-Runoff by
hydrological model NAM and preparing the Flood Hazard map in the lower water shed using
MIKE-11,MIKE-21 and MIKE-FLOOD. These products and inputs were employed to simulate
stream flow in the Great Gibe Watershed. The study period 2000-2012 was used for
downloading and extracting the selected satellite rainfall estimates with daily-temporal and 0.250
x 0.250 spatial resolution.
Sensitivity and uncertainty analysis, calibration and validation of the model were done using
MIKE ZERO particularly the Sequential Uncertainty Fitting (SUFI-2) algorism for all rainfall
inputs independently. The calibration period was from 2001-2005 leaving one years as a-warm up
period and the validation period was from 2006-2012 for satellite rainfall based simulations as
well as in situ based simulations. Based on the modeling results of Mike Zero models had showed
better performance when calibrated with the in situ rainfall with model performance efficiency of
Mean Absolute Error, Maximum Values and Standard Deviation models respectively while, the
satellite rainfall estimates (TRMM-3B42v7 and CMORPH) showed relatively good performance
when calibrated on the models with Mean Absolute Error (5.21,4.24), Max.Val. (73.74,32.97) and
Std. Deva.(7.46,4.24) in the case of Asendabo with relative to the ground based measurements in
both satellite based product respectively. But, PERSIANN satellite rainfall estimates showed poor
performance for all Mean Absolute Error (3.78), Max. Values (33.06) and Std. Deva. (4.24)
before bias corrected.
The model output simulation results performance in analyzed of Rainfall-Runoff based up on the
coefficient of determination and Nash-Sutcliffe coefficient, during the calibration it is found to be
0.509 and 0.64 respectively and the total water balance error during calibration is 14.75%. And
during validation period 0.645 and 0.675 respectively with the total water balance error is 17.5%.
Peak and low flows between observed and simulated hydrograph were found matching well. The
simulated minimum and maximum runoff for 13 years’ period the maximum annual runoff varies between 1466.3 mm to 7525.4 mm. The simulated runoff was maximum for the month of August
(6977.4 m3/s) and minimum for the month of April (5540.6 m3/s). The single flood event of year
100 in the upper part of Gibe confluence flood plain simulated using MIKE FLOOD, which
integrated the calibrated and validated 1D MIKE-11 hydrodynamic model with 2D hydrodynamic
model MIKE-21 for the flood plain.
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Keywords
Great-Gibe, Rainfall-Runoff, MIKE-11, MIKE-21, MIKE-FLOOD TRMM3B42v7, PERSIANN, CMORPH