Water Atlas of the BLUE NILE SUB-BASIN

Water Atlas of THE BLUE NILE SUB-BASIN

Draft

Eastern Nile Technical Regional Office (ENTRO) , 2006 page - Draft

Eastern Nile Technical Regional Office (ENTRO) , 2006 page - Table of Content

Introduction 1 Quick Overview of the Eastern Nile Basin

General 3 1.1. Location of Baro-Akobo-Sobat Basin .2. Administrative Units .3. Demography .4. Economy .5. Historical and Cultural Places

Land Surface Feature 4 .1. Topography .2. Slope and Terrain .3 Relief 2.3. Land and River Profiles

Climate 5 .1. Rainfall .2. Air Temperature .3. Evaporation .4. Humidity Land 6 4.1. Land use /Land Cover 4.2. Soil 4.3. Geology 4.4. Vegetation Hydrology 7 5.1. River network and Catchments 5.2. Sub-Basin Runoff volumes and Water resource 5.3. River System Schematics andDraft Indicative Water Balance 5.4. Sediment Infrastructure and Utilities 8 6.1. Dams and reservoirs 6.2. Irrigations and Agriculture 6.3. Hydropower and Electric 6.4. Communication and Transport Environmental 9 7.1. Land Degradation 7.2. Water quality Problems 7.3 Parks , wetlands and Protected areas 7.4 Water related Disease

Eastern Nile Technical Regional Office (ENTRO) , 2006 page - Draft

Eastern Nile Technical Regional Office (ENTRO) , 2006 page - Introduction

The Eastern Nile Technical Regional Office (ENTRO) is an organization meant to realize ENSAP (Eastern Nile Subsidiary Action Program) in the EN countries, namely Egypt, Ethiopia and Sudan. ENSAP seeks to realize the NBI Shared vision for the EN region aimed at reducing poverty, foster economic growth and the reversal of environmental degradation.

Currently, under ENSAP, planning is underway for the multipurpose development of the region. .To support its multipurpose development objectives, ENTRO proposes to synthesize information at sub basin level categorized in three themes namely, Water Resources, Environment and Socioeconomy. To implement this objective the base line data compilation at national level has been conducted for the three EN countries and compiled a report for each theme at national level. The present assignment is aimed at bringing the national level compiled data in to a sub basin level synthesized data, considering no boundary of the EN countries.

The objective of this consultancy work is thus to synthesize essential information on water and related resources at sub basin level. The national level compilations are to be synthesized at sub basin level so that information’s on these three themes could be presented at sub basin level, which can be used for proper planning of both resources and further investigation activities on resources in the Eastern Nile Sub-basins under the EN Multipurpose Development Program.

This work includes the preparation of the main report and sub basin level atlas preparations that could be annexed to the main report. This atlas specifically prepared for the Blue Nile sub basin is part of the four annexes that supports the main report This atlas is a summarized version of the main report with a more de- clarative fashion supported by few explanations and more base maps with the objective of providing basic features of each sub basin for decision makers and senior program/project coordinators. Draft

Eastern Nile Technical Regional Office (ENTRO) , 2006 page - Draft

Eastern Nile Technical Regional Office (ENTRO) , 2006 page - Quick Over View of the eastern Nile Basin The Eastern Nile Basin is constituted of three riparian countries namely Egypt, Ethiopia and Sudan. A very few portion of Eritrea (4214km2, Tekeze Master Plan Studies, May 1998) is also included in the Nile system. Egypt, with an estimated total area coverage of 997,739km2 (ENTRO Atlas, Jan 2006), is located in the upper north portion of the Nile occupying the entire lower course of the ENB including its mouth at the Mediterra- nean Sea. It is bounded on the north by the Mediterranean Sea; on the east by the Gaza strip, Israel and Red Sea; on the south by Sudan and on the west by Libya. The country has a maximum length of 1,105km stretching from north to south, with a maximum width at its south border, stretching east-west for some 1130km. Less than 10% of its area is identified to be cultivable, the bulk of its skin coverage (more than 90%) being desert where life could hardly survive. With a total area of 69722km2 the Nile watershed in Egypt accounts only 7% of the country and 4% of the ENB.

Ethiopia, Africa’s oldest independent country, is located in the horn of Africa, bounded on the northeast by Eritrea and Djibouti, on the east & south east by Somalia, on the south west by Kenya and on the west and northwest by Sudan. With total skin coverage of 1,133,380km2, Ethiopia is believed to be the major contributor (about 85% of the Nile inflow at Aswan) of the Nile annual inflow at Aswan. The highland plateau of the country (above 1800masl) is identified to be the heart of the country covering some 60% of its skin area. The Great Rift Valley splits the Ethiopian highland plateaus diagonally in northeastern and southeastern directions. The northeastern half largely drained by the Nile system. The plateaus are characterized with deep valleys and canyons cut by numerous rivers and streams drained by 12 major river basins, Abbay (the Blue Nile) being one of them taking the lion share both in terms of skin area coverage (18% of the country) and water resources potential (more than 50%). Ethiopia is the source of the Tekeze, Blue Nile and Baro-Akobo sub basins, which are believed to be the major contributor of the Nile water. Including the upper courses of Tekeze, Abbay & Baro-Akobo sub basins; the Nile watershed in Ethiopia accounts about 32% of the skin area of the country and 22% of the ENB. The Sudan, located in the northeasternDraft Africa and the largest land state (2,505,800km2) in the continent, is bounded on the north by Egypt, on the east by the Red Sea, Eritrea, and Ethiopia; on the south by Kenya, Uganda, & Democratic Republic of the Congo, and on the west by the Central Africa Republic, Chad, and Libya. The maximum stretch in Sudan is from North to South with a diameter of 2250km, along with its east- west extreme stretch width of 1730km. About 50% of Sudan is included in the Nile watershed. Contributing only 15% of the Nile inflow at Aswan, 74% of the ENB is located within the Sudanese land,

Eastern Nile Technical Regional Office (ENTRO) , 2006 page - Total Skin Area of ENB Countries and their Coverage of ENB Countries (their Respective Total Area Vs their Respective Area in the ENB Coverage in the ENB) Egypt 7% 2505800 3000000

2500000

2000000 997739 1133380 1220085 1500000

1000000 368037 69722 ENB Country Area (km2) 500000 Sudan Ethiopia 49% 32% 0 Egypt Ethiopia Sudan ENB Countries

The ENB is constituted with four major contributing sub basins; the Baro-Akobo-Sobat-White Nile sub basin (with mean annual inflow of 26bm3, that contributes 30% of the inflow at Aswan) from its southern tip, the Blue Nile (at 51bm3 contributes 60% of the inflow at Aswan) located in its middle-east direction, the Tekeze-Setite-Atbara sub basin (contributing 12bm3 per year & accounts 12% of the Nile inflow at Aswan) in its northeastern portion and the Main Nile in its lower course downstream of the Khartoum junction, at its northern tip.

Sub Basin Areas Sub Basins Area Coverage in the ENB System Baro-Akobo- Main Nile Sobat WN 40% 28%

656397 Main Nile 219570 Tekeze-Setite- Atbarta 313660 Blue Nile 468217 Baro-Akobo- Blue Nile Sobat WN Tekeze-Setite- 19% Atbarta 0 200000 400000 600000 800000 13% Area (km2)

According to the OSI socioeconomic report (ENTRO, Jan 2007, draft) the total population residing in the ENB is estimated at 148,775,920 (projected toDraft 2005). In the same report it is however, reported as 160million. Egypt with a total population of 77million in the ENB (1105person/km2 one of the worlds highest density) watershed accounts 52% of the population in the ENB. Ethiopia, with its total ENB population (population in the upper courses of the three ENB sub basins) of 48,400,000 (135 persons/km2) , being the second largest populous state in the ENB, accounts 33% of the ENB population. Sudan with a total ENB population of 23,375,920 (20person/km2) accounts 16% of the ENB population and is the least populous country in the ENB.

Eastern Nile Technical Regional Office (ENTRO) , 2006 page - The Baro-Akobo-Sobat-WN sub basin (12,410,000) covers 8% of the ENB population. The Blue Nile, the Tekeze-Setite-Atbara and the Main Nile sub basins with a total population of 44,457,200; 14671000; and 77,237,720 covers 30%, 10% and 52% of the ENB population respectively. Crude population densities (ppkm2) in the four sub basins: Baro-Akobo-S-WN, Blue Nile, Tekeze-Setitite-Atbara and Main Nile, is estimated at 27, 142, 67 and 118 respectively.

ENB Population Size by Sub Basin in the Year 2005 ENB Population Coverage by Country in the Year 2005 Population Densities in the ENB Sub Basins

Egypt Ethiopia 51% 33% Main Nile 77237720 118

Main Nile Tekeze-Setite-Atbarta 14671000 67

Tekeze-Setite- Atbarta Blue Nile 44457200 142

Blue Nile 27 Baro-Akobo-Sobat 12410000 WN Baro-Akobo-Sobat WN 0 10000000 20000000 30000000 40000000 50000000 60000000 70000000 80000000 Sudan 0 50 100 150 No of Population 16% Population Density (person/km2)

Currently irrigated agriculture is practiced in the lower course of both the Blue Nile, WN and in the Delta, at the mouth of the Nile. In Sudan current irrigation development is estimated at 1.5million hectares (Water Watch, Aug, 2006) and in Egypt it is about 3.25million hectares (Egypt Water Component OSI Report, Jan 2006). In Ethiopia, current irrigated agriculture practice is virtually none existence. Draft

Eastern Nile Technical Regional Office (ENTRO) , 2006 page - 1. Generals 1.1 Location of The Blue Nile Sub-Basin

The Blue Nile sub basin, located in the middle east of the Eastern Nile Basin, is the largest contributor 56bcm/year, of the Eastern Nile Basin system accounting 67% of the inflow at Aswan. The Gelgel Abbay, one of the major tributaries of Lake Tana, is believed to be the head of the Blue Nile. Gelgel Abbay starts in the highland plateaus of Gojjam flowing in a general north direction to Lake Tana.

Geographically the Blue Nile sub basin extends from 320 27’ East to 39050’ east and from 160 5’ North to 70 40’ north.

The Blue Nile Sub-Basin Draft

Location of the Blue Nile Sub-Basin

Data/Information Source :One System Inverntory Synthesis Report 2007

Eastern Nile Technical Regional Office (ENTRO) , 2006 page - 10 Map - 1.1 : Location Map of The Blue Nile Sub- Basin

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Eastern Nile Technical Regional Office (ENTRO) , 2006 page - 11 1.2 Administrative Units of The Blue Nile Sub-Basin

The sub basin is constituted by tthree regional states In Ethiopia , : Amhara (93,565km2) , Beni- Shangul-Gumuze (44,676km2) and Oromiya region (62478km2) with a total area of 202994km2 Ethiopa, (64%) are included Its counter part in Sudan is 36% constituted from five states: Sennar (30,106km2), Blue Nile (19162km2), El-Gezira (15686km2), Gadrife (38829km2) and Khartoum (6880km2), which all together covers 110,663km2, and Sudan, accounts 36% of the total sub basin at Khartoum, 64% its mouth.

100,000 93565 90,000

80,000

70,000 62478 60,000

50,000 44676

Area(km2) 38829 40,000 30106 30,000

19162 20,000 15686

10,000 6880

0 Sinnar Blue Nile El Gezira Gadrife Khartoum Amhara Beni-Shangul- Oromiya Gumuze Area of Adminsitrative Units within the Blue Nile Sub Basin

Gaderif; 5% Sinnar; 5% Khartoum; 9% Amhara; 46% DraftEl-Gezira; 8%

Blue Nile; 1%

Beni-Shangul Oromiya; 24% Gumuze; 2% Population distribution by administrative division within the Blue Nile Sub Basin

Data/Information Source :One System Inverntory Synthesis Report 2007

Eastern Nile Technical Regional Office (ENTRO) , 2006 page - 12 Map - 1.2 : Administrative Divisions of the Blue Nile Sub-Basin

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Eastern Nile Technical Regional Office (ENTRO) , 2006 page - 13 1.3 Demographic Characteristics of The Blue Nile Sub-Basin

The Blue Nile sub-basin is the second highly populated 106 sub-basin of the four sub-basins of the Eastern Nile 104 Basin system. Accordingly, it is home to an estimated 102 104.7 102 100 44, 457,210 people, and accounting 28% of the total 98 100 96 population of the Eastern Nile Basin. 96.7

Ratio (M: Per 100F) 94 92 Located in Ethiopia, the Abbay Basin comprises the Illubabor Abbay South Sudan Watershed Gondar major part of the Beni-Shangul-Gumuze and Amhara Sex Ratio in the Blue Nile Sub Basin Regional States and some portion of the Oromiya

Regional State. According to the 1994 Population Average Lefe-expectancy in the Blue Nile Sub Basin and Housing Census of Ethiopia, the Basin had an 70 57.3 60 52.4 estimated population of 22.6 million, which was 46 49.6 50 projected to reach 30.7 million in 2005. This indicates 40 a 35% population increase in the Basin during the last Age 30 ten years after the most recent census in the country 20 10 0 The Blue Nile watershed downstream of the border Male Ethiopia Female Ethiopia Male Sudan Female Sudan extends from the Blue Nile State bordering Ethiopia Average Life-expectancy in the Blue Nile Sub Basin in the southeast, downwards to the Khartoum state at Khartoum in the general north direction. The estimated 140 population of the Basin Nile sub-basin in the Sudan in 120 100 130 129 2004 was 13,400790 with average annual growth rate 115 104 80 92 of 2.7% and projected to 13,757,200 to the year 2005. 89 83 86 60 Number 40 The sub Basin constitutes three regional states in 20 Ethiopia and five states in Sudan and it is characterized 0 Blue Nile Gadarif Khartoum El-Gezira Sennar Amhara BS-Gumuz Oromiya by a range of socio-economic and ecological variations. Infant Mortality Rate in the Blue Nile Sub Basin per 1000 The Blue Nile and the main Nile route in Sudan are Live Births divided as the southern and northern zones, on the basis of the wide diversity in the nature of the landscape Gaderif; 5% Sinnar; 5% DraftKhartoum; 9% Amhara; 46% between the scrub and tropical forest of the south and the desert in the north. The southern zone stretches El-Gezira; 8% from the Sudan-Ethiopian borders to Khartoum State, which land area also includes the states of Blue Nile, Blue Nile; 1%

Sennar, Gezira, Gadrife and Khartoum. The northern Beni-Shangul Oromiya; 24% Gumuze; 2% zone extends from north of Khartoum State down to Population distribution by administrative division within the Northern State, which borders with Egypt and falls the Blue Nile Sub Basin in the main Nile sub basin.

Data/Information Source :One System Inverntory Synthesis Report 2007

Eastern Nile Technical Regional Office (ENTRO) , 2006 page - 14 Map - 1.3 : Population density map of the Blue Nile Sub-Basin

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Gaderif; 5% Sinnar; 5% Khartoum; 9% Amhara; 46%

El-Gezira; 8%

Blue Nile; 1%

Beni-Shangul Oromiya; 24% Gumuze; 2% Population distribution by administrative division within the Blue Nile Sub Basin

Eastern Nile Technical Regional Office (ENTRO) , 2006 page - 15 1.4 Economy of The Blue Nile Sub-Basin

The upper course of the sub basin, agriculture largely primitive in nature, is the major occupation, where more than 85% of employment is coming from. In the highlands agriculture is largely below subsistence level dominated with low-level technologies.

The JAM (2005) defined the poverty rate in Sudan as the population below 40% of economic status index on asset ownership basis. Unfortunately the index is not defined. The poverty line in Ethiopia is set using a basket of food items sufficient to provide 2200kcals per adult per year. Together with a non-food component this represents EBirr 1,070 in 1995/96 prices. It is evident that the two measures are not directly comparable.

In Sudan the JAM report estimates the following poverty rates for states within the basin:

Kassala 41% to 60% 60 Gaderif 41% to 60% 50 Nahr El-Neil 21% to 40% 40 Red Sea 61% to 70% 30 50 65 55 50 20 32 38 30 In Ethiopia estimates were made for those regions in 10 0 the sub basin and presented as: Kassala Gaderif Nahr El- Red Sea Amhara BS-G Oromiya Neil Regional States Rural Urban Total poverty rates for states within the Blue Nile basin Amhara 32% 35% 32% BS-G 56% 41% 55% Oromiya 37% 49% 38%

In all regional states rural rates had declined since Children 1995 and urban rates had increased. Old Age 7

Draft 85

Dependacy Ratio in the Blue Nile (Ethiopia) Per 100 Working Population (15 to 64 age)

Data/Information Source :One System Inverntory Synthesis Report 2007

Eastern Nile Technical Regional Office (ENTRO) , 2006 page - 16 Draft

Eastern Nile Technical Regional Office (ENTRO) , 2006 page - 17 1.5 Cultural and Historical Locations of The Blue Nile Sub-Basin

The well -trodden path through Ethiopia’s famous and fascinating historic places takes you through a scenically magnificent world of fairy -tale names, such as Lalibela, Gondar, Deber Damo and Bahar Dar. Gondar and Bahar Dar being located at the heads of the Blue Nile sub basin.

Several of Ethiopia’s more remote areas are excellent for walking safaris, which are offered by several good tour operators in the country. Walking tours, best planned for the dry season, offer the traveler the opportunity for awe-inspiring vantage points from which to view many of Ethiopia’s natural wonders, cultural riches and architectural heritage. In Gondar, there are fairy-tale castles dating back to the 17th century.

Gondar was the 17th Century capital of Ethiopia, and is notable for its medieval Castles and churches. The City’s unique imperial compound contains a number of Castles built between 1632 and 1855 by the various Emperors who reigned during this period. These dramatic castles, unlike any other African, display a richness in architecture that reveals the Axumite traditions as well as the influence of Arabia.

Other treasures of Gondar include the 18th Century palace of Ras Beit, the bath of Fasilades, the ruined palace of Kusquam, and the church of Debre Berhane Selassie with its unique murals.

Bahar Dar is a small town set on the south - eastern shore of Lake Tana, where local fishermen still use papyrus boats, and just 30 km from the spectacular Tiss-Essat Falls. Here the Blue Nile creates “Smoking Water” an awe-inspiring sight as it plunges into the gorge below.

From Bahar Dar one must explore some of the ancient monasteries that have been built around Lake Tana, or on the many Islands. These include Dek Stephanos with its priceless collections of icons, as well as the remains of several medieval emperors, Kebran Gabriel and Ura Kidane Mehret with its famous frescoes. The colourful local market at Bihar Dar is renownedDraft for its weavers and wood workers.

Eastern Nile Technical Regional Office (ENTRO) , 2006 page - 18 Draft

Eastern Nile Technical Regional Office (ENTRO) , 2006 page - 19 2. Land Surface Feature

2.1 Topography Characteristics of The Blue Nile Sub-Basin

Topographic map of the sub basin generated using satellited based elevation information(DEM) , indicates two major land forms in the system. The mountainous topography largely located in the Ethiopian highlands in its eastern portion and the flat low-lying areas of the sub basin starting close to the Ethio-Sudan border and extending westwards in to the Sudanese land to Khartoum, the mouth of the sub basin. The low-lying areas have an altitude that ranges from 500masl (at and around the border) to 340masl around Khartoum. This surface of the sub basin has some undulating features with just the occasional granite jebel rising above the clay plain. The lowland in the Rahad and Dindir watersheds (b/n Atbara and the Abbay watershed) is covered by the Butana plains.

In the Eastern portion of the sub basin the topography is characterized with highland plateaus well above 2000masl to 2500masl with isolated volcanic ruminants rising to 3500masl to 4200masl. The Abbay river and its tributaries are deeply incised in these highland plateaus leaving an undulating and rolling topographic features which forms a series of isolated tablelands separated by the deeply incised valleys and gorges. Around the border, in the Ethiopian territory, the lowlands having an altitude that ranges from 600masl to 1000masl have undulating and rolling topographic features demarcating the transition b/n the highland plateaus in the eastern portion to the flat low-lying plain in the western portion of the sub basin.

Altitude Based DEM Classification of the BN SB

30 24 25 22 20 18

15 13 13

10 7 Coverage (%) 5 2 0.3 0 Draft 342-500 500-1000 1000- 1500- 2000- 2500- 3000- 3500- 1500 2000 2500 3000 3500 4261 Altitude Classes

Eastern Nile Technical Regional Office (ENTRO) , 2006 page - 20 Map - 2.1 : Elevation Model of the Blue Nile Sun- Basin

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Eastern Nile Technical Regional Office (ENTRO) , 2006 page - 21 2.2 Terrain and Landform of The Blue Nile Sub-Basin

The flat land form with slope less than 5% covers (44%) nearly half of the sub basin. Land forms with gentle slope (5% to 10% land slope) covers 13% of the sub basin and land slope exceeding 20% covers 20% out of which land slope exceeding 30% covers 6%. The remaining 22% of the basin has land slope in the range of 105 to 20%. From Lake Tana (1785masl) to the Ethio-Sudan border (500masl) the Blue Nile traverses a total distance of about 1000km with an average river bed slope of 1.5%.

Land Slope Classification Coverage (%) for BN SB as Produced from DEM Files

0-5 5~10 10~15 15~20 20~25 25~30 >30

6 6 8 44

12 13

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Eastern Nile Technical Regional Office (ENTRO) , 2006 page - 22 Map - 2.3 : Terrain Map of Blue Nile Sub-Basin

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Eastern Nile Technical Regional Office (ENTRO) , 2006 page - 23 2.3 Relief of The Blue Nile Sub-Basin

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Eastern Nile Technical Regional Office (ENTRO) , 2006 page - 24 Map - 2.2 : Reliefe Map of The Blue Nile Sub-Basin

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Eastern Nile Technical Regional Office (ENTRO) , 2006 page - 25 3. Climate

3.1 Climate-Rainfall in The Blue Nile Sub-Basin

The climate of the BN is dominated by two factors: its near-equatorial location and an altitude ranging from below 500masl at its mouth to more than 4000masl in the highland plateaus of Ethiopia. The influence of these factors determines the rich variety of local climates, ranging from hot and desert like along and d/s of the Sudan border, to temperate climates on the highland plateaus, and cold climates on the mountain peaks. The climates in the highland plateaus of the BN is largely characterized with dry months in the winter and mean annual rainfall of above 1200mm. Beyond the border, mean annual rainfall is reduced to less than 500mm, and further reduced to 180mm at Khartoum. From the border to Khartoum hot tropical climate dominates

50.00% Blue Nile Sub Basin Rainfall Isohytes 45.00%

40.00%

35.00%

30.00% 25.26% 25.23% 25.00%

19.24% 20.00%

15.00% 10.61% 9.14% 10.00% 5.36% 5.16% 5.00%

0.00% 150-400 400-600 600-900 900-1200 1200-1300 1300-1500 1500-1800

With weighted mean annual rainfall of above 1000mm the effective rainfall is estimated to be 300mm at Khartoum and above 500mm at the Ethio-Sudan border. Altitude in the upper course of the sub basin ranges from below 1500masl to well above 2000masl. This reach of the sub basin is well known for its high rainfall that ranges from 1000mm to above 1500mm. Hydrologic variability in the highlands of the sub basin is significant (ranging from 20% to more than 30%) and flood problems are serious cases at its mouth, at Khartoum. Floods are also important in the upper course of the sub basin as in the case of the Lake Tana sub basin. Recurrent flooding is significantly affecting a number of households residing in the flood plains of Fogera, Dembia, & Bichign around LakeDraft Tana.

Eastern Nile Technical Regional Office (ENTRO) , 2006 page - 26 Map - 3.1 : Rainfall Map of Blue Nile Sub-Basin

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Eastern Nile Technical Regional Office (ENTRO) , 2006 page - 27 3.2 Climate-Temprature in The Blue Nile Sub-Basin

Temperature and evaporation are observed to have good correlation with altitude in the Blue Nile sub basin.

At high altitudes (>2300masl) in the western highland plateau of Ethiopia mean annual temperature is reported to be in the range of 17oC to 19.5oC. Close to the Ethio-Sudan border where altitude is lowered to less than 1000masl, temperature rises ranging from 24oC to 26.5oC. At is mouth, around Khartoum, altitude is below 500masl and temperature ranges from 28.5oC to 30.5oC

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Eastern Nile Technical Regional Office (ENTRO) , 2006 page - 28 Map - 3.2 : Temprature Map of Baro-Akobo-Sobat and White Nile Basin

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Eastern Nile Technical Regional Office (ENTRO) , 2006 page - 29 3.3 Climate-Evaporation in The Blue Nile Sub-Basin

Variation of evaporation does flow the same pattern as that of temperature. In the upper course, evaporation is less due to high altitudes. Mean annual evaporation ranges from about 1500mm (Fiche station (.2300masl) in the high lands of the sub basin) to more than 6800mm around Khartoum, the mouth of the sub basin (fig 4.9 & fig 4.10). Horizontal variation of evaporation is also significant. In the southern half of the upper course, mean annual evaporation is even below 1500mm and in its north half, especially at its northern tip evaporation is above 1800mm.

Spatial Variation of Evaporation in the Blue Nile Sub Basin 8000 Mean Annual Evap(mm) 7000

6813 6000 Mean Annual Evap (mm) 5000

4000 4685 3938 3000

2000 2038 1635 1622 1000 1514 1302

0 Bahir Dar Fenote- Debre- Alem Ketema Agaro El-Damazine Sennar Khartoum Selam Markos Stations Draft

Eastern Nile Technical Regional Office (ENTRO) , 2006 page - 30 Map - 3.3 : Evaporation Map of The Blue Nile Sub-Basin

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Eastern Nile Technical Regional Office (ENTRO) , 2006 page - 31 3.4 Climate-Humidity in The Blue Nile Sub-Basin

Half of the sub basin is identified to have a mean annual relative humidity of above 55%. Some 16%, largely located in its mouth, is identified as dry area with mean annual relative humidity of less than 40%.

Blue Nile Relative Humidity areal Distribution

55-60 65-68 60-65

50-55 3 30 5 -3 -4 5 0 45-50 40-45 27-30

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Eastern Nile Technical Regional Office (ENTRO) , 2006 page - 32 Map - 3.4 : Reletive Humidity Map of Blue Nile Sub-Basin

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Eastern Nile Technical Regional Office (ENTRO) , 2006 page - 33 4. Land

4.1 Land use and Land Cover of The Blue Nile Sub-Basin

The five major land use land cover units in the sub basin constitute sedentary rain-fed crop land (26%), grass land (25%), wood land (17%), shrub-land (12%), and semi-mechanized farm (10%). Irrigated crops (2.6%), rock surfaces (2.4%), high forest areas (1.4%). Water bodies (1.3%), shifting rain-fed crops (1.1%) etc are the minor land use land cover units which all together constitutes 10.7% of the sub basin

Rainfed Crops: Sedentary GrasslandLand Use Land Cover Coverage(%)Woodland in the BN Sub Basin Shrubland Semi-mechanised farms Irrigated Crops Rock High forest Water Rainfed Crops: Shifting Plantation Sand Seasonal sw amp Permanent sw amp Urban Afro-alphine

10.0 11.8 2.6 16.8 2.4 1.4 0.4 0.7 25.0 25.8 0.2 0.2

Blue Nile Sub Basin Landuse Land Cover

9000000 8000000 7000000 Area(ha) 6000000 5000000 4000000 Area(ha) 3000000 2000000 1000000 Draft 0 Rock Sand Water Urban Plantation Woodland Shrubland Grassland High forest Afro-alphine Irrigated Crops Seasonal swamp Permanent swamp Rainfed Crops: Shifting Semi-mechanised farms Rainfed Crops: Sedentary Landuse Unit

Eastern Nile Technical Regional Office (ENTRO) , 2006 page - 34 Map - 4.1 : LandCover Map of The Blue Nile Sub- Basin

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Eastern Nile Technical Regional Office (ENTRO) , 2006 page - 35 4.2 Soil of The Blue Nile Sub-Basin

Soils Coverage in the Blue Nile Sub Basin 2.8 2.8 3.6 5.1 28.9

12.7

18.7 23.9 Vertisols Nitisols Leptosols Luvisols Water Body Cambisols Regosols Alisols

Phaeozems Fluvisols Swamp Solonchaks

Along the international boundary a demarcation b/n the vertisols and Nitisols exists. The Nitisols covering 24% of the sub basin largely covers the western highlands while the eastern highlands are covered by the less fertile leptosols (19%). The unconsolidated sediments of the Sudan lowland plain are categorized as vertisols covering 29% of the sub basin. The highland plateaus of Ethiopia with flat land slope are covered with extensive vertisols. Luvisols of better fertility and deep in depth are dominantly covering the flood plains surrounding Lake Tana. Draft

Eastern Nile Technical Regional Office (ENTRO) , 2006 page - 36 Map - 4.2 : Soil Map of the Blue Nile Basin

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Eastern Nile Technical Regional Office (ENTRO) , 2006 page - 37 4.3 Geology of The Blue Nile Sub-Basin

The geologic map of the sub basin indicates the sub basin is dominated with three geologic features, the base rocks, the basement complex, acidic & metamorphic rocks and the unconsolidated sediments of Vertisol nature.

The bas rocks of basaltic origin dominate in the eastern highland plateaus of the sub basin in Ethiopia and along the boundaries of the BN and Atbara -Tekeze sub basins. The lowlands of Ethiopia largely close to the international boundary and some portions in the lower course of the Rahad and Dindir watersheds are largely covered with basement complex, acidic and metamorphic rocks. The central part of the Gezira scheme, starting from the international boundary including considerable portion of the Khartoum state are predominantly covered with unconsolidated sediments of largely clay in nature.

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Eastern Nile Technical Regional Office (ENTRO) , 2006 page - 38 Map - 4.3 : Geology Map of Blue Nile Basin

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Eastern Nile Technical Regional Office (ENTRO) , 2006 page - 39 4.4 Vegetaion Cover of The Blue Nile Sub-Basin

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Eastern Nile Technical Regional Office (ENTRO) , 2006 page - 40 Map - 4.4 : Vegetation Map of Blue Nile Basin

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Eastern Nile Technical Regional Office (ENTRO) , 2006 page - 41 5. Hydrology

5.1 Drainage and Cathement of The Blue Nile Sub-Basin

The Abbay river (Abbay refers to u/s of the border that is the Blue Nile in Ethiopia) is the second largest sub basin in Ethiopia and sub divided in to 16 major watersheds namely: Deddessa (19943km2), South Gojjam (17029km2), Guder (7123km2), Anger (8027km2), Lake Tana (15300km2), North Gojjam (14618km2), Dabus (21367km2), Beshilo )13453km2), Fincha (4154km2), Muger (8318km2) Jemma (16033km2), Welaka (6517km2), Wombera (13,163km2), Beles (14426km2), Rahad at border (8401km2) and Dinder at border (15,128km2) which constitutes a total of 202,884km2 in the Ethiopian Territory. Its counter part in Sudan has the Blue Nile, Rahad and Dinder major watersheds with estimated area of 110,663km2. The Blue Nile at Khartoum, its mouth, is estimated to have a total drainage area of 313,547km2 , indicating nearly 65% of the BN sub basin is in Ethiopia, contributing nearly 100% of the total sub basin inflow at Khartoum

Area(km2) 350000 311382 300000 Area(km2) 250000 200719 200000

150000 110663 93565 100000 38829 50000 30106

r le ra e m m a e a m m a i i if u u r z iy u u n N z r o S a u S to in e e d rt h m m r S u G a a n m u ro ia a l l G h a A G p h B E d l- O io K K u u h t S g t a n E e a il h N S i- e n lu e B B l ta o T The Blue Nile starts at the outflow of Lake Tana located in its southern tip at Bihar Dar. Blue Nile flows in a relatively shallow river banks, in a general south direction on medium altitude (1800masl) plateau for some 30km and at Tiss Esat (water that smokes) it is plunged with a 50m deep fall, usually known as Tiss Esat Fall, which then after it enters in to the Abbay/Blue Nile gorge. The Blue Nile, then drains the Gojjam highlands (part of the Central highland plateaus of Ethiopia with an altitude reaching to more than 4000masl) in its right bank and the North Gondar, South Wollo and North Showa highland plateaus (also part of the central highland plateaus of Ethiopia) in its left bank. The Blue Nile after entering the gorge, flows in a clock wise spiral and initially in a general south direction, collecting runoff from its major tributaries such as Beshilo, Walaka, and Jemma in the left bank and Abeya, Suha, and Muga (as part of the South Gojjam Watershed) in its right bank. From the Addis-Bihar Dar highway bridge and d/s, the Blue Nile flows in a general west directionDraft following the same clockwise pattern and collects runoff from the west Showa and Wellega highland plateaus (part of the western highland plateaus of Ethiopia) in its left bank through its major tributaries Muger, Fincha, Angar, Deddessa, and Dabus and in its right bank collecting runoff from the Gojjam highland plateaus (part of the Central and western highland plateaus of Ethiopia) through its major tributaries such as Yeda, Chemoga, Birr, Fettam, Dura and Beles, all together identified as the South Gojjam watershed. The Dabus in the left and the Beles in the right are the two major contributors joining the BN close to the border.

D/s of the border; the BN is intercepted with the Roseires reservoir after entering some 100km in to the Sudanese land. No major tributaries join the system in this reach. D/s of the Roseires dam the Sennar dam is located on the main stem of the system. Two major tributaries entering the system d/s of the Sennar reservoir are Dindir and Rahad, both of them originated from the north western highland plateaus of Gondar in Ethiopia. In general the Sudan counterpart of the Blue Nile sub basin is sub divided in to five major watersheds.

Eastern Nile Technical Regional Office (ENTRO) , 2006 page - 42 Map - 5.1 : Drainage Network and Catchments

Draft

Eastern Nile Technical Regional Office (ENTRO) , 2006 page - 43 5.2 Surface water resource of The Blue Nile Sub-Basin

Accounting more than 65% of the Aswan inflow at Khartoum (the mean runoff of the Nile at Khartoum estimated at 74bcm), Blue Nile is the major contributor in the Nile system in general and in the ENB sub system in particular. The mean annual inflow at Abbay Kessie station (1980-2000) is estimated at 17.4bcm. The watershed area at Kessie station is estimated at 65784km2, which is about one-third of the Abbay watershed at the border. The effective runoff generated by the watershed u/s of the Kessie station is estimated to be 265mm. Considering the 1980 to 2000 years of record, the Blue Nile at the border yields mean annual inflow of 51bcm with effective runoff of 285mm indicating the runoff generated in the south portion (Guder, Anger Dedessa, and Dabus watersheds) is considerably high. At the outlet of Lake Tana the inflow to the Blue Nile system is estimated at 3.7bcm (effective runoff being 240mm) indicating the runoff generated b/n the border and the lake outflow is about fourteen times the lake outflow. Alike the mean annual rainfall, effectiveness of rainfall in terms of runoff generation decreases northwards. The unrestricted mean annual runoff at Khartoum is estimated at 56bcm, resulting an effective runoff of 180mm. However, after abstractions for different uses (largely for irrigation), records from 1980 to 2000 indicate that the Blue Nile mean annual inflow at Khartoum is estimated at 48bcm.The reduction in effective runoff west wards in the sub basin is largely attributed to the vast low-lying plain starting from the international boundary to Khartoum characterized with low mean annual rainfall.

Inflow Distribution of the Blue Nile at Sennar Station Seasonal Distribution of Runoff for Rahad & Dindir at their Respective Mouth (After Sutcliffe & Parks Feb 1999) 8000 1200 7000 1000 Rahad (1907-97) 6000 Mean Rahad (1908-97) 5000 Max 800 Min 4000 600

Runoff (m3/s) 3000 400 2000

Mean Monthly Inflow (mcm) 200 1000 0 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Seasons (months) months

The runoff contributed from the 16 majorDraft watersheds is presented in the table below. Downstream of the border, Rahad and Dindir, both originated from the south-western highland plateaus of Ethiopia, are the major contributors to the sub basin with all together discharges mean annual inflow of 4bcm to the Blue Nile system.

Monthly Inflow Distribution of Blue Nile at Ethio-Sudan Border (1961-79) 8000 7000 6000 Mean Border Max Min 5000 4000 3000 Max, Min) 2000 1000 Discharge (m3/s, Mean, 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Months

Eastern Nile Technical Regional Office (ENTRO) , 2006 page - 44 Map - 5.2 : River Runoff Map of Blue Nile Sub-Basin

Draft

Eastern Nile Technical Regional Office (ENTRO) , 2006 page - 45 5.3 Indicative waterbalace of The Blue Nile Sub-Basin

The 16 major watersheds in the Abbay u/s of the border and the extension of these watersheds in Sudan named as the Blue Nile, Dindir and Rahad are the major watersheds (section 3.5.1) and river systems constituted the rivers schematic of the sub basin.

Indicative water balance for the Blue Nile system is presented in fig below. The water balance accounts abstractions in the system. Evaporation is not implicitly presented in the system due to data shortage at Roseries and Sennar reservoirs in the Sudan. From the data available for the sub basin, the Blue Nile provides mean annual inflow of 51bm3 at the border, 49.3bm3 at the Roseries station, indicating a loss of 1.73bm3 b/n the border and the Roseries station. Most of the irrigation abstractions in the Sudan are made from the Sennar reservoir and through pumping d/s of the Sennar reservoir. Mean annual abstraction for the reach b/n the Roseries and Khartoum is averaged at 6.38bm3. The Rahad and Dindir rivers contribute man annual inflow of 4.0bm3 to the Blue Nile main stem d/s of the Sennar reservoir. This makes the mean annual inflow of the Blue Nile before Khartoum to be 53.3bm3. After accounting the abstractions for irrigation, mean annual inflow reaching the Khartoum node is stated as 46bm3. Data recorded in the Blue Nile at Khartoum (1900 – 1995) is averaged at 48.7bm3 (usually taken as 50bm3 in most of the reports including the water component OSI report of the Sudan). As a result it is believed that the long-term mean annual inflow of the Blue Nile at Khartoum is averaged at 48.7bm3. The Blue Nile alone is thus believed to contribute 65% of the inflow to the Main Nile at Khartoum.

Draft

Eastern Nile Technical Regional Office (ENTRO) , 2006 page - 46 Map - 5.3 : Flow Schematics of Blue Nile Sub-Basin

Draft

Eastern Nile Technical Regional Office (ENTRO) , 2006 page - 47 Sediment in Blue Nile Sub-basin The sediment load at the Ethio-Sudan border is estimated at 140Mt/yr. Sediment inflow from the watershed u/s of the Beles-Abbay confluence is estimated at 138.8Mt/yr. The trapping efficiency at the Roseries reservoir is estimated at 15% and an average of 21.08Mt/yr sediment is deposited. The Sennar with trapping efficiency of 10% is depositing a mean annual sediment load of 11.56Mt/yr. The Dindir and Rahad rivers, d/s of the Sennar reservoir, yields mean annual sediment inflow of 9.2Mt/yr. In the reach b/n the Dindir-Rahad & Blue Nile confluence to Khartoum sediment deposit takes place along the river banks and in the flood plains at a rate of 6.32Mt/yr with retention efficiency of 2.5%. Accordingly, the sediment load reaching the mouth of the sub basin at Khartoum is estimated at 99.04Mt/yr.

Sedimentation of reservoirs and irrigation canals is one of the most priority development concerns in the d/s reach of the sub basin. The report from the Sudan water OSI component indicate that the Roseries and the Sennar reservoirs have respectively lost some 35% and 60% of their total storage capacity due to reservoir sedimentation resulted from high sediment inflow from the highland portion of the sub basin. The Roseries and the Sennar were initially designed at a reservoir capacity of 3.5bcm and 0.5bcm respectively. Further more siltation in the irrigation infrastructures (canals, division boxes etc) in the well known Gezira scheme is a priority concern causing the maintenance cost virtually routine and expensive

Design Storage Capacity Vs Current (2000) Storage Capacity for Reservoirs in the BN-Sudan Design Storage Current Storage(2000) 4000 3354 3000 2227 2000 930 1000 Storage (Mm3) 370 0 Sennar Roseires DraftReservoirs

Eastern Nile Technical Regional Office (ENTRO) , 2006 page - 48 Map - 5.4: Sediment in Blue Nilie Sub- Basin

Draft

Eastern Nile Technical Regional Office (ENTRO) , 2006 page - 49