Trend Analysis Of Runoff And Sediment Fluxes In The Upper Blue Nile Basin: A Comparative Analysis Of Statistical Tests, Physically-based Models And Land Use Maps | 10364
Journal of Ecosystem & Ecography
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The landuse/cover changes in the Ethiopian highlands have significantly increased the variability of runoff and sediment fluxes
of the Blue Nile River. The objectives of this study were (i) to understand the long-term variations of runoff and sediment
fluxes using statistical models, (ii) to interpret and corroborate the statistical results using a physically-based hydrological model
(SWAT), and (iii) to validate the interpretation of SWAT results by assessing changes of landuse maps. Firstly, Mann-Kendall
and Pettitt tests were used to test the trends of Blue Nile flow (1970 to 2009) and sediment load (1980 to 2009) at the outlet of
the Upper Blue Nile basin at El Diem station. These tests showed statistically significant increasing trends of annual stream flow,
wet season stream flow and sediment load at 5% confidence level. The dry season flow showed a significant decreasing trend.
However, during the same period the annual rainfall over the basin showed no significant trends. Secondly, the SWAT model
was used to simulate the runoff and sediment fluxes in the early 1970s and in 2000s in order to interpret the physical causes of
the trends and corroborate the statistical results. A comparison of model parameter values between the 1970s and 2000s shows
significant change, which could explain catchment response changes over the 28 years of record. Thirdly, a comparison of landuse
maps of 1970s against 2000s shows conversion of vegetation cover into agriculture and grass lands over wide areas of the basin.
The combined results of the statistical tests, the SWAT model, and landuse change detection are consistent with the hypothesis
that landuse change has caused a significant change of runoff and sediment load from the Upper Blue Nile during the last four decades
Tesfay Gebretsadkan Gebremicael has completed his M.Sc. at the age of 27 years from UNESCO-IHE Iinstitute for Water Education, The
Netherlands. He is the head of Natural Resources Management Research programme of Tigray Agricultural Research Institute. He has published
more than 6 publications, 2 Journal, 1 book and three proceeding in a conference.
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