About Eastern Nile
The Eastern Nile sub-system: This covers the
catchments of the Blue Nile (Abay), Atbara (Tekezze),
and Baro. The runoff from this region contributes
between 85 and 90 per cent of the annual Nile flows,
but the Blue Nile (Abay) can be seen to respond
directly to the seasonal rain patterns, exhibiting
clear dry and wet spells. The Eastern Nile supports
an extraordinary range of ecosystems from high
mountain moorlands, afromontane forests, savanna
woodlands, extensive wetlands, intensively
cultivated catchments, groundwater systems, and arid
Eastern Nile Basin
A river basin is a land mass dissected by
tributaries as they flow downstream and join each
other to form larger and larger rivers. The Nile
Basin looked at southward from the delta in
Alexandria, Egypt, is one such large basin. The Nile
Basin in turn is divided into several sub-basins,
the Eastern Nile being one of them. The Eastern Nile
basin covers some 2,695,300 km2, which in turn is
sub divided into sub basins that include Main Nile
(covering 44 %), the Baro-Akobo-Sobat and White Nile
(26 %), the Abbay/Blue Nile (17 %), and the Tekeze-Atbara
It is estimated that more than 156 million people
live in the four sub basins of Eastern Nile.
The Abbay/Blue Nile and Main Nile are the
most heavily populated, accounting 79 % of the total
population. Each of these sub-basins offers
distinctive natural resources potentials and
constraints that entail the need for context-
specific short- and long-term development
Abbay-Blue Nile Sub Basin
The Abbay-Blue Nile Sub-Basin covers 311,548 km2 (35
and 65 percent of which is in Sudan and Ethiopia
respectively). Seventy and thirty percent of the
population lives on the Ethiopian and Sudanese sides
Abbay's source is Gish Abbay in West Gojam,
Ethiopia, which flows northward as the Gilgel Abbay
into Lake Tana. Three major rivers (Megech, Rib and
Gumara) also flow into Lake Tana. The Abbay exits
from the southeastern corner of the lake, cuts a
deep gorge first south then westwards, later joined
by a number of tributaries: Beshilo, Derame, Jema,
Muger, Finchaa, Didessa and Dabus from the east and
south; and the Suha, Chemoga, Keshem, Dera and Beles
from the north. The Abbay exits Ethiopia near
Bambudi and becomes the Blue Nile in Sudan.
The Dinder and Rahad (seasonal rivers) rise to the
west of Lake Tana, flow westwards across the border
joining the Blue Nile below Sennar in Sudan. The
Blue Nile meets the White Nile at Khartoum.
Mean annual discharge of Abbay
(1920-2000) at the Sudanese border is
approximately 50.0 km3, additional 4.0 km3 coming
from Rahad and Dinder. In contrast to the more
steady White Nile, considerable seasonal flow
the Abbay/Blue Nile -
ranging from 302 million m3/month in February
to a peak of 13,151 million m3/month in August
(annual peak flow occurs July-October).
Abbay has a channel length of 922 km to the Sudan
border. Abbay falls 1295 meters to the Sudan border
(490 masl), beginning with the spectacular Tissat
Falls in Lake Tana (1,785 masl). There is a 10-fold
increase in discharge between Lake Tana and the
Sudan border. Rainfall in Abbay-Blue Nile Sub-Basin
ranges from nearly 2,000 mm/yr in the Ethiopian
Highlands to less than 200 mm/yr at the junction
with the White Nile.
Abbay-Blue Nile Sub-basin land use consists of:
farming - small scale sedentary and semi-mechanize
(36%); irrigated land (3%); grassland and woodland
(42%); high forest (1.4%); swamp (0.5%); rock
(2.4%); water body (1.3%); other (15%).
Main Nile Sub Basin
The Main Nile sub-basin covers 656,398 km2, from the
confluence of the Blue and White Niles in Khartoum
to the Delta in Egypt in the North, covering
over 14 degrees of latitude. Tekeze-Atbara
River is the only tributary along the Main Nile.
Except in years of exceptional rainfall there is no
Meroe dam in Sudan is located between
Khartoum and the Aswan High Dam at the Fourth
The average annual flow of the Main Nile at Tamaniat
is approximately 72.691 km3 (1911 – 1995). The river
flows through a series of cataracts with a total
drop of 192 m (from 375 masl at Khartoum to 183 masl
at Lake Nubia/Nasser) over a length 1,490 kms.
Though there are year-on-year variation, the
total annual flow at the border with Egypt has
historically been taken (before any significant
abstraction) as 84 km3 (1905-1959).
In Sudan the annual rainfall ranges from less than
25 mm in the north to 400 mm. In Egypt most rain
falls along the coast but even the wettest area,
around Alexandria, receives only about 200 mm of
precipitation per year.
Sixty five percent of the Main Nile Sub-Basin
is categorized as bare land and bare soil, 14
percent is loose sand, 13 percent covered by grass
and shrub, 4 percent is under irrigated land and 0.2
percent is woodland. The remaining portion of the
sub basin land is used for other purposes.
The Tekeze-Atbara sub-basin covers an area of
227,128 km2, including the Mereb-Gash basin.
Sixty percent of the Sub-Basin falls in Sudan
and 40 % in Ethiopia. Seventy five percent of the
population lives in Ethiopia.
The Tekeze River travels more than 750 km
from its source near Lake Ashange in Ethiopia to the
border with Sudan. In Sudan
the river extends another 575 km in a north-westerly
Sudanese portion of the Tekeze-Atbara watershed is
characterized by very low density of watercourses
except in the south-west along the Blue Nile
watershed where there are numerous intermittent khor
The Atbara River contributes 12.7 % of the total
discharge of the Main Nile. The average discharge at
Kashm el Girba station (1986-2000) was 11.45 km3.
The total runoff is 52,834 m3 water per km2
per annum, compared with 169,612 m3/km2/yr for the
Blue Nile, 28 833 m3/km2/yr for Baro-Akobo-Sobat.
Most of the Tekeze-Atbara water comes from Ethiopia,
even though 50 % of the Sub-Basin is located in
Rainfall in the sub-basin ranges from about 2 120
mm/yr in the highlands of Ethiopia to less than 50
mm/yr at the junction with the Main Nile at Atbara.
Sixty two percent of
the Sub- Basin
covered under grass land and shrub land, 12 %
is categorized as bare land with
loose sand’ 10 % under small scale rain fed
sedentary agriculture, 4 5 is woodland, 3 % rock,
1.2 % under irrigated crops, forest land accounts
0.1 Other land uses cover the remaining portion.
The Baro-Akobo-Sobat- White Nile Sub-basin
The Baro-Akobo-Sobat-White Nile Sub-basin covers
468,215 km2 (84% is in Republic of South Sudan and
16 % in Ethiopia). Nearly 80% of the population
lives in Republic of South Sudan.
The main tributaries of the Sobat are the
Baro, Gilo and Akobo that rise on the Ethiopian
Plateau at some 3,300 masl. The Highlands are
covered in dense
although this is rapidly being converted to
agriculture. The plains below are covered with a
Lowland Baphia Forest that gives way to savanna
woodland and then swamp grassland plains.
The Baro-Sobat-White Nile Sub-basin within Ethiopia
is well-watered. However, spatial variation of the
mean annual rainfall is considerable due to the
great range in elevation across the basin. Average
annual precipitation ranges between 600 mm in the
lowlands (less than 500 masl), and 3,000 mm in the
highlands (over 2,000 masl). Average rainfall
greater than 100 mm occurs from May to October.
Highest rainfall occurs June-September.
Within Republic of South Sudan the highest rainfall
(greater than 1000 mm/year) is found in the
southwest and southeast of the Sub-basin. Over much
of the Pibor-Sobat Sub-basin
it varies between 750 and 1,000 mm/yr. In the White
Nile Sub-basin rainfall decreases northwards from
750 to 250 mm near the junction of the White and
Blue Niles. However, everywhere rainfall exhibits
both seasonal and year-on-year variability.
Variability increases form south to north.
Grass and open shrub land is the dominant land cover
constituting 52 % of the total land in the
Sub-Basin. Open wood land covers 17 %, 7% is under
permanent and seasonal swamp, 4 % sedentary crop
land, 2% irrigated crop, and 18 % under other uses.
The Eastern Nile Countries
The Eastern Nile riparian countries include
Ethiopia, Sudan and South Sudan, Egypt, and a small
portion of Eritrea (about 3,500 km2):
The most downstream country, with more than 96% of
its freshwater inflow originating from outside its
national boundaries, is also the most economically
developed. Its population was estimated at 82.5
million and GDP per capita at USD 2781 (World Bank,
2012). About 96% of the population lives within the
Nile basin. Egypt is one of the founding members of
the NBI (ENTRO, 2013).
Ethiopia is the most upstream country with a
population of 84.7 million and a GDP per capita of
USD 374 (World Bank, 2012). The highlands of
Ethiopia generate over 86% of the
Nile waters. The Nile basin covers 32% of the
national land area and 40% of the population resides
with in the basin. Ethiopia is one of the founding
members of the NBI (ENTRO, 2013).
of South Sudan
South Sudan is the youngest state encompassing
portions of the White Nile and the Nile above the
confluence of the Sobat and White Nile Rivers. The
population of South Sudan is 10.3 million (World
Bank, 2012). This area includes the extraordinary
wetland, the Sudd, which controls the flow from the
Equatorial Lakes region into the White Nile. About
97% of the country and 99% of the population falls
within the Nile Basin. South Sudan joined NBI in
2012 (ENTRO, 2013).
Sudan is the mid-stream country. Sudan has a
population of 34.3 million and GDP per capita of USD
1234 (World Bank, 2012). It receives the flows of
White Nile, Abbay/Blue Nile, Baro- Akobo-Sobat and
Tekeze-Setit-Atabra tributaries. Khartoum is where
the two Niles meet to form the Main Nile. About
74.9% of the country and 87% of the population
resides with in the Nile Basin. Sudan is one of the
founding members of the NBI(ENTRO, 2013).