Water Resource System Modeling of Eastern Nile River Basin
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Date
2015-06
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Addis Ababa University
Abstract
This study was conducted to quantify the likely impacts and benefits of current and future
development options in the Blue Nile basin using simulation approach. Four cases studies were
investigated under different scenarios; i) the filling strategy of the under-construction Great
Renaissance Dam (GERD), ii) the long term GERD operation case study iii) strategic
development perspective case study that includes all proposed dams upstream of GERD in
Abbay-Blue Nile and iv) future irrigation development in the Eastern Nile. Mike Basin and Mike
Hydro River Basin Simulation Models were used.
The results indicate 6 years filling period is mostly sufficient to fill the GERD reservoir with no
impact on the current irrigation water use of Egypt. However, if a rare scenario of 6 years dry
consecutive sequence of flow that was observed in the 1980s occurs, the filling strategy need to
be revised. Analysis of the hypothetical scenarios within -/+ 20 flow variation from the long term
mean indicates the 6 years filling sequence lower than the normal (mean) flow by up to 10% will
be in the tolerable range of filling.
In terms of long term analysis, once GERD reservoir is filled and started operation, it imposes no
threat to the existing agricultural water use on downstream countries (Sudan and Egypt).
However, the annual energy production from HAD may be reduced by 6 to 8% due to the
reduction in the head available at the Dam in Egypt. Overall, the presence of GERD renders
more regional benefit than before. The mean energy in Eastern Nile region could increase by
more than 120%. If additional proposed dams are developed as strategic option in the Abbay-
Blue Nile sub basin, up to 56,000 GWh/year of energy can be produced without significant
iv
impact on regional agricultural water uses. The upstream country Ethiopia can generate as much
as 38200 GWh of Energy and the energy production in Sudan increases by 38%.
However, expansion of irrigated agriculture in the Eastern Nile basin generally may impact both
the hydropower and existing agricultural water uses downstream of GERD. Analysis based on
planned irrigation development in the basin indicates, water availability is a major constraint that
limits irrigated agriculture expansion. The planned irrigation development in Sudan and Ethiopia
may reduce water availability for agriculture by as much as 26.3% in the Eastern Nile basin. The
possibility of more large-scale irrigation exists in the basin, but it is not close to the extent of
planned development. As the study utilized the planned irrigation development by the countries,
comprehensive regional planning and coordinated water management scenario, which is not
covered under this study, may yield a better overview of irrigation expansion in the basin.
This study is a comprehensive analysis of the impacts and benefits of hydropower and irrigation
development in the Eastern Nile basin and may lay a basis for future scientific engagement in the
basin. Hydropower development in the upper reaches of Abbay-Blue Nile basin is enormous and
renders distinct possibility for future development beyond the completion of GERD. However,
planned large scale expansion of irrigated agriculture introduces water deficit to both energy and
agriculture production and requires coordinated regional planning and analysis for optimal
economic and social returns to the basin. The future holds a great deal of uncertainty in terms of
socio-economic and political changes that influence development decisions. To take full
advantage of the water resources of the basin it is necessary the basin be managed as a single
system which requires the establishment of an effective institutional mechanism that aim to
develop the river in a shared-vision and cooperative way. Furthermore, future climate change
may put additional uncertainties to the Eastern Nile basin development. Therefore, it is suggested
that analysis of water resources development in Eastern Nile Basin shall explore opportunities
using probabilistic approaches under various level of regional cooperation scenarios.
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Keywords
Eastern Nile Basin, Basin Simulation Models were used