Abay Basin Water Allocation Modelling Using Hec Ressim
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Date
2009-10
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Addis Ababa University
Abstract
Despite Ethiopia possesses abundant water resources potential, second only to
Congo in all of Africa, the country is at critical cross roads with large and increasing
population, a depressed national economy, insufficient agricultural production and
low no of developed energy sources. 83% of Ethiopians lack access to electricity; only
5 percent of irrigable land and 3% of the hydropower potential in the Blue Nile basin
has been developed so far. Nowadays persisting drought and increasing competition
for water have left Ethiopia with no more chance other than seeking solutions and
assure sustainability of the resource.
Even though Ethiopian portion of Blue Nile, Abay possesses a great potential of
irrigation and hydropower developments, the financial and political constraints have
long hindered the country’s development. This study aims at analyzing the effects of
implementing the potential irrigation and hydropower projects that are
contemplated in the country.
Reservoir system simulation (Hec-ResSim) software has been used to study the out
puts of executing different developments in the basin. This has been done by setting
up the model and simulating for four scenarios including the base scenario referring
to the current situation in the basin. After a curious filtering of all projects mentioned
in the basin’s master plan and other project specific reports, 315,431ha (38.7% of
total 815,581ha potential) of irrigation and 7,026Mw (89.6% of total 7845Mw
potential) of hydropower potential; overall comprising 23 dams having a combined
maximum storage capacity of 170.15Bm3 have been preferred to be analyzed and
assessed using the model. After categorizing these projects under four scenarios; the
simulation has been done based on 33 years (1960-1992) of monthly hydrologic flow
series.
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This study under has indicated that If Ethiopia is to develop 315,431ha and 7,029Mw,
the resulting decline in the cross border flow will be only 3,382.93Mm3 which is only
7.29% of the currently simulated (under current condition scenario,scenario-1) Abay
discharge to Sudan which is 46,396.99 Mm3. Under this condition both Ethiopia and
Sudan benefit from regulation of Abay by Ethiopian dams, in that it results in
increasing of low flows, giving the whole system uniformity of balance, decreasing
water escaping during flood seasons.
As concluded from this study regulation works upstream in Ethiopia have resulted in
a uniform monthly average flow of 3,584.51Mm3 throughout the year to Sudan.
Currently as the base case simulation indicated, Sudan receives monthly average low
flow of 1,233.54Mm3 through November to June which then turns to be increasing;
August being flood month when 13,456.27Mm3 has been observed.
In addition if Ethiopia is to develop 7,029Mw including hydropower projects on the
tributaries, then some 38,385.81Gwh/annum of electricity will be produced. Even
though Tana-Beles project imposes a big deal of inflow and power out put decline on
the main stream hydropower plants, this power decrease was exceeded by the
power generated at Tana-Beles power plant. Prior to Tana-Beles project Power
output from main stream plants has been 34,284.23 Gwh/annum then increased to
34,736.14 Gwh/annum despite power decrease at Karadobi, Mabil, Mandaya and
Border.
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Keywords
Using Hec ; Ressim