Validating Satellite Based Rainfall Product and Hydrological Modeling in Blue Nile Jemma Sub-Basin
No Thumbnail Available
Date
2021-09-16
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Addis Ababa University
Abstract
Water resource management absolutely depends on water resource data like rainfall and stream
flow. Better quality of such data are obtained by direct measurement via interconnected
gauging instruments. Due to limited resource, gauging instruments’ distribution are not dense
enough, in turn causes water resource data scarcity. Currently, Satellite rainfall estimates are
available with good spatial and temporal resolutions. However, they are estimates rather than
direct measurements. Thus, as the study was begun to evaluate the performance of satellite
based rainfall product, TRMM_3B42; it was validated in Jemma sub-basin, and its raw and
combined version was evaluated as input of distributed type of HEC-HMS model in Gumerrow
catchment. For the achievement of the objectives, collected hydro-meteorological, satellite
remote sensing and Arc-Info data were processed with appropriate tools like R-programing
language, Arc-GIS model builder, HEC-HMS and others. Results also were presented using
graphical techniques, categorical and continuous statistics, and model evaluation statistics.
The Satellite based rainfall product and Ground rain-gage data were comparable except some
important variations. In categorical rainfall values, the overall accuracy of Satellite rainfall
estimate was greater than 78.7%, which was observed in Light rain type of daily timescale.
However, the stated algorism has faced special difficulty in daily timescale with more false
alarms. In continuous rainfall values, Positive linear association was detected in daily, monthly
and seasonal timescales with correlation coefficient values of 0.52, 0.915 and 0.926 respectively.
And an average underestimation of Satellite rainfall estimate was discovered in all timescales.
Among seven HEC-HMS model parameters, Potential max retention factor (S) was obtained
as the most sensitive parameter in Gumerrow catchment. Raw Satellite rainfall estimate
showed poor performance in calibration period of (2003-2006) with NSE, PBIAS, RSR and
R2 values of 0.406, 24.26%, 0.771 and 0.417 respectively. However, the performance had
improved significantly to good enough with NSE, PBIAS, RSR and R2 values of 0.532, 14.83%,
0.684 and 0.554 respectively when combined version was used as input of HEC-HMS model.
Relative to calibration period, improved performance was discovered in validation period
of (2007-2008) with NSE, RSR and R2 values of 0.452, 0.74 and 0.477 respectively for raw
Satellite rainfall estimate, and 0.56, 0.663 and 0.618 respectively for combined version.
Description
Keywords
Jemma Sub-Basin, TRMM_3b42, Combined Version, Gridded Data, Distributed HEC-HMS Model